Virginia Tech Tree Fruit Extension and Outreach Programs

2021 Tree Fruit Extension Survey

S. Sherif — Fri, 08 Oct 2021 21:36:26 GMT

Greeting,

The following is a link for a very brief survey that should take less than 2 min to complete. The results of this survey will help us assess our tree-fruit research and extension program at the AHS Jr. AREC. This survey will also help us identify priority areas and extension activities most preferred by Virginia tree fruit growers and stakeholders.

Here is the survey link:

https://virginiatech.qualtrics.com/jfe/form/SV_dcZlZMMDx5SbKGa

We appreciate your help!

Apple Maturity Report-Winchester Sep 30-2021

S. Sherif — Thu, 30 Sep 2021 14:17:53 GMT

DA readings refer to the level of chlorophyll (green color) in the fruit, just below the skin. DA values decrease proportionally with fruit ripening. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the harvest date for most commercial apple varieties. Generally speaking, fruits intended for CA should be picked at starch index (3-5), firmness (> 16 lb), and DA reading (around 0.60). Fruits intended for fresh consumption should be harvested at starch index (5.5-7), firmness (13-16 lb), DA reading (0.35), and Brix (12-14%).

Chlorpyrifos Tolerances for to be Revoked in 2022

Chris Bergh — Fri, 24 Sep 2021 13:52:34 GMT

As we have expected for a while, a final ruling on chlorpyrifos (Lorsban, Yuma, Warhawk and other generics) has been issued by the EPA. Earlier this week, the EPA provided a comprehensive document that addresses questions about this issue, which can be found at the link below.

https://www.epa.gov/ingredients-used-pesticide-products/frequent-questions-about-chlorpyrifos-2021-final-rule

The statements below, copied from that document, summarize the rationale for the decision and provide the date on which tolerances for all commodities will expire.

“Based on the currently available data and taking into consideration the currently registered uses for chlorpyrifos, EPA is unable to conclude that the risk from aggregate exposure from the use of chlorpyrifos meets the safety standard of the Federal Food, Drug, and Cosmetic Act (FFDCA). Accordingly, EPA is revoking all tolerances for chlorpyrifos. This final rule is effective October 29, 2021. The tolerances for all commodities expire on February 28, 2022”.

Importantly, any commodity treated with chlorpyrifos during the 2021 growing season will not be affected by this ruling and can be sold into the marketplace. Another practical consideration is that the final allowable applications of chlorpyrifos would target peach borers and, if necessary, dogwood borer, this fall. Thereafter, it will not be available for pest management in spring 2022.

Any remaining stocks of products containing chlorpyrifos will need to properly disposed of. This may include the pesticide collection program operated by VDACS. Although their program for 2021 has ended, VDACS will be working with Cooperative Extension agents in the coming months to determine the locations where collections will be conducted in 2022, which appear to include most of the areas relevant to Virginia tree fruit growers. Mark Sutphin has provided me with two links that relate to the VDACS collection program, and I have copied them below, for your information. We will continue to provide updates on any new developments that may arise with respect to the disposal of remaining stocks.

https://www.vdacs.virginia.gov/pesticide-collection.shtml

https://www.vdacs.virginia.gov/map-of-participating-localities.shtml

Apple Maturity Report-Winchester Sep 22-2021

S. Sherif — Wed, 22 Sep 2021 18:43:30 GMT

Apple Maturity Report-Winchester Sep 16-2021

S. Sherif — Thu, 16 Sep 2021 18:22:05 GMT

DA readings refer to the level of chlorophyll (green color) in the fruit, just below the skin. As the fruit ripens, chlorophyll levels decline. Therefore, low DA values are indication of advanced fruit maturity. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the harvest date for most commercial apple varieties. Generally speaking, fruits intended for CA should be picked at starch index (3-5), firmness (> 16 lb), and DA reading (around 0.60). Fruits intended for fresh consumption should be harvested at starch index (5.5-7), firmness (13-16 lb), DA reading (0.35), and Brix (12-14%).

Apple Maturity Report-Winchester Sep 2, 2021

S. Sherif — Fri, 03 Sep 2021 21:28:06 GMT

Apple Maturity Report-Winchester Aug 26, 2021

S. Sherif — Fri, 27 Aug 2021 16:18:41 GMT

Starch index was assessed for 12 apple varieties grown in the AHS Jr. AREC, Winchester, VA, on Aug 18
, 2021.
To get information about the starch index, iodine solution recipes, and different maturity indices please refer to our blog post at https://blogs.ext.vt.edu/tree-fruit-horticulture/2012/08/23/harvest-maturity-resources/

Apple Maturity Report-Winchester Aug 18, 2021

S. Sherif — Wed, 18 Aug 2021 18:01:45 GMT

Starch index was assessed for 12 apple varieties grown in the AHS Jr. AREC, Winchester, VA, on Aug 18
, 2021.
To get information about the starch index, iodine solution recipes, and different maturity indices please refer to our blog post at https://blogs.ext.vt.edu/tree-fruit-horticulture/2012/08/23/harvest-maturity-resources/

Section 18 request for dinotefuran withdrawn

Chris Bergh — Tue, 17 Aug 2021 14:53:00 GMT

Following conversations with VDACS, some of my eastern tree fruit colleagues, and representatives from the companies that market Venom and Scorpion, I have notified VDACS that we wish to withdraw the request for a Section 18 Emergency Exemption for dinotefuran for the 2021 season. This will influence growers only in VA, PA, and WV, as several of the original participants (NC, NJ, MD) have declined to participate for the last 1-2 years. Further, I have notified VDACS that a request will not be submitted in 2022 or thereafter. There are several reasons for this. In the short term, one factor is that the EPA must respond to submissions regarding this request received during the public comment period in spring 2021, and would not likely accomplish this on time for its use this year. Importantly, a Section 18 exemption is intended to be a short-term response to an emergency situation. Given that we have received approval for dinotefuran use under a Section 18 every year since 2011, this process has more than run its course with the EPA.

Therefore, dinotefuran cannot be used in pome fruit. In stone fruit, it can be applied only at the rates labelled under its Section 3 registration, which are lower than allowed on the previous Section 18 labels. Whether a Section 3 registration for dinotefuran in tree fruit will eventually happen remains to be seen, and is a matter for the companies and the EPA.

As you know, a Section 18 for bifenthrin (Bifenture, Brigade) for BMSB in apples and stone fruit has been in place for the 2021 season since earlier this month, and will expire on Oct. 15. We hope that a Section 3 registration for bifenthrin will occur, but again, that remains to be determined.

We do have products, including bifenthrin, some of the other pyrethroids, and some of the neonicotinoids that can provide adequate protection against BMSB, particularly given that its current populations are considerably lower than what they were in the early years of the outbreak.

Apple Maturity Report-Winchester Aug 13, 2021

S. Sherif — Sat, 14 Aug 2021 16:18:22 GMT

Below is the apple maturity report for the Winchester/Fredrick county area (Table 1). We measured fruit firmness (lb), fruit color, total soluble solids (Brix), and starch conversion rate (1-8 index) for 12 apple cultivars grown in the AHS Jr. AREC’s and we will keep sending similar reports throughout the harvest season to help you determine the optimal harvest time for your apple varieties. More varieties will be added to the table below as we move through the harvest season. We have assessed fruit firmness, Brix, and starch index according to the methods we described previously in another blog post (https://blogs.ext.vt.edu/tree-fruit-horticulture/2012/08/23/harvest-maturity-resources/). We used a DA meter to measure fruit coloration. The DA device measures the chlorophyll content in the fruit, just below the skin. As the fruit ripens, chlorophyll degrades, and DA readings decline accordingly. Starch index, fruit firmness and, ‘to some degree’, Brix values, are used either alone or in combination to determine the harvest date for most commercial apple varieties. In Table 2, you will find the estimated firmness and starch index values at which apples should be harvested for controlled atmosphere (CA) storage and fresh consumption. If you don’t see your variety in the list, you can generally harvest your crop at starch index (3-5), firmness (> 16 lb), and DA reading (0.60) for CA storage. But if the crop is intended for fresh market, then wait until starch index of (5.5-7), firmness (13-16 lb), DA reading (0.35) and Brix (12-14%). Again, there are varietal differences, so it’s always recommended to use more than one maturity index to determine the optimal harvest time.

Table 1: Apple Fruit Maturity Report for Winchester/Fredrick County-Aug 13-2021
DA readings refer to the level of chlorophyll (green color) in the fruit, just below the skin. As the fruit ripens, chlorophyll levels decline. Therefore, low DA values are indication of fruit maturity. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the harvest date for most commercial apple varieties. Generally speaking, fruits intended for CA should be picked at starch index (3-5), firmness (> 16 lb), and DA reading (around 0.60). Apples intended for fresh consumption should be harvested at starch index (5.5-7), firmness (13-16 lb), DA reading (0.35), and Brix (12-14%).

Starch index was assessed for 12 apple varieties grown in the AHS Jr. AREC, Winchester, VA, on Aug 13
, 2021.

This table was adapted from the Michigan State University Website

Test message 8.10.21

Chris Bergh — Tue, 10 Aug 2021 16:45:14 GMT

This is just a test to determine whether or not my recent posts are being delivered to subscribers.

Section 18 for use of Brigade WSB, Bifenture EC, and Bifenture 10DF against BMSB in apples, peaches, and nectarines in Virginia

Chris Bergh — Fri, 06 Aug 2021 15:54:01 GMT

On August 5, 2021, the Environmental Protection Agency (EPA) approved the renewal of a Section 18 Emergency Exemption for use of the bifenthrin-based products, Brigade WSB, Bifenture EC, and Bifenture 10DF against brown marmorated stink bug (BMSB) in apples, peaches, and nectarines in Virginia. This exemption applies only to the products mentioned above. These and other bifenthrin-based insecticides have a Section 3 label for use in pears. The requirements of this Section 18 are that applications must be made only from the ground, at a rate of 0.08 to 0.2 lb active ingredient (a.i.) per acre, with not more than 0.5 lb a.i. per acre per season. These application rates equate to 5.12 – 12.8 fl oz of Bifenture EC, and 12.8 – 32.0 oz of Bifenture DF or Brigade WSB per acre. Seasonal maximums are 32 fl oz of Bifenture EC, 80 oz of Bifenture DF, and 72 oz of Brigade WSB. Multiple applications may be made per season, at a minimum retreatment interval of 30 days. The REI is 12 hours and the PHI is 14 days. This insecticide is extremely toxic to fish, aquatic invertebrates, and bees, and all precautions to avoid these exposures must be observed. Bifenthrin is considered one of the strongest insecticides against BMSB but can be disruptive to natural enemies of secondary pests. Consequently, we recommend its use in apples later in the season, when BMSB populations are highest. In peaches and nectarines, it can be useful until 14 days before harvest. This Emergency Exemption expires on October 15, 2021. A petition to support a Section 3 registration for bifenthrin in these crops is under review with the EPA.

CM and OFM Degree Days and Optimal Spray Timing, 7.26.21

Chris Bergh — Mon, 26 Jul 2021 17:32:03 GMT

ReTain and Harvista For Pre-Harvest Drop Control of Apples

S. Sherif — Sun, 25 Jul 2021 21:52:33 GMT

The pre-harvest drop refers to the abscission of fruits from the tree before horticultural maturity. Depending on the cultivar and growing season, yield losses due to pre-harvest drop can reach 30%. Factors such as heat and drought stress, heavy insect infestation, and late summer pruning can increase the severity of fruit drop. Early-maturing cultivars (e.g., Gala and Honeycrisp) are usually more prone to fruit drop than late-maturing cultivars (e.g., Fuji and Pink Lady). Ethylene, the ripening hormone, is considered the primary driver of pre-harvest drop, and therefore ethylene inhibitors are used to control the pre-harvest drop in apple orchards. ReTain (from Valent Bioscience) and Harvista (from AgroFresh) are the two ethylene inhibitors labeled for pre-harvest drop control in Virginia. ReTain inhibits the biosynthesis/production of ethylene, whereas Harvista prevents ethylene reception and action. The purpose of this blog post is to share with you the results of two experimental trials we conducted in the 2018 and 2019 seasons to explore the effects of different rates and application timings on the efficacy of these materials.

In 2018: we examined two rates of ReTain (166g/acre and 333g/acre) and three application timings (1 week, 3 weeks and (1 & 3) weeks before the anticipated harvest date) on the percentage of fruit drop (%) of Gala apples. We used 6 trees per treatment. We flagged and counted 100 fruit/tree at 4 weeks before harvest (WBH), and we counted the fruits on these trees every week starting at 1 WBH through 4 WAH. The percentage of fruit drop (%) at each stage was calculated relative to the initial fruit count. In addition to fruit drop, we also investigated the effects of different treatments on fruit quality parameters (fruit weight, size, firmness, color, sugar content, starch index, and acidity). The findings of this trial can be concluded in four points: a) The effect of ReTain treatments on fruit drop was more evident at 1 and 2 weeks after harvest. b) Applying ReTain at the full rate (333g/acre) 3 weeks before the anticipated harvest date reduced fruit drop by 40-50% and extended the harvest season by 1-2 weeks. The same results were obtained when ReTain was used at half rate (166g/acre) at 1 and 3 WBH. C) fruits treated with ReTain (full rate) were firmer, had a lower starch index and lower brix than the untreated checks. However, ReTain-treated fruits were generally less colored than untreated checks. D) no differences in fruit size were found between ReTain- treated and untreated fruits. (Please refer to Tables 1 & 2).

Table 1: The effects of ReTain rate and application timing on the pre-harvest fruit drop (%) of Gala apples-Season 2018.

Silwet L-77 (0.1 %; 388 ml/100 gal) was added to all spray applications.
Values sharing the same letters are not statistically significant.
WBH: weeks before harvest; WAH: weeks after harvest.

Table 2: Gala fruit quality as affected by ReTain applications- 2018.

Color was measured by a DA meter; lower I_AD values indicate advanced fruit maturity.

In 2019: we examined 2 rates of ReTain (333 g/acre and 666 g/acre), 1 rate of Harvista (121 fl oz/acre), 3 application timings for ReTain (at 1, 3 and (1&3) weeks before harvest) and 2 application timings for Harvista (at starch index 2 and at starch index (1.5 and 3). Again, six trees were used per treatment. The total number of fruits on each tree was counted four weeks before harvest. The percentage of fruit drop was calculated starting at 1 WBH and through 3 WAH. We also examined the effects of different treatments on the fruit quality of Gala apples at harvest. Our results indicated that: a) a full rate (333 g/acre) of ReTain applied at 3 WBH was not statistically different than a double rate (666 g/acre); b) Harvista applied twice (at starch index 1.5 and 3) showed better results on fruit drop than the single application (at starch index 2); c) There were no significant effects on fruit size and weight when either ReTain or Harvista were used; d) Fruits treated with ReTain were generally firmer than control, but had poor coloration; e) Harvista did not improve fruit coloration, but also did not reduce it compared to control; f) ReTain applications at a full rate significantly reduced the fruit’s ethylene content, but it required two applications of Harvista to acquire the same effect. (Please refer to Tables 3 & 4)

Table 3: ReTain and Harvista effects on the pre-harvest fruit drop (%) of Gala apples-2019

DBH: days before harvest; WBH: weeks before harvest

Table 4: ReTain and Harvista effects on fruit quality of ‘Gala’ apples-2019

Color was measured by a DA meter; lower I_AD values indicate advanced fruit maturity. Ethylene (ET) content was quantified per each fruit using gas chromatography. Higher ET levels indicate advanced maturity.

Other general notes:

6h drying time after ReTain and Harvista applications is required for achieving better results.
For optimal results, ReTain and Harvista should be applied with 100 gal/acre as a complete spray.
ReTain label allows the use of up to two pouches per acre either as a single spray or as a split application for apple.
Harvista can be applied close to anticipated harvest date (within 3 days prior to harvest).

CM and OFM Degree Days and Optimal Spray Timing, 7.22.21

Chris Bergh — Thu, 22 Jul 2021 13:30:05 GMT

CM and OFM Degree Days and Optimal Spray Timing, 7.19.21

Chris Bergh — Mon, 19 Jul 2021 14:35:15 GMT

Tree Fruit Pathology Survey for Dr. Srdjan Acimovic

Chris Bergh — Fri, 16 Jul 2021 17:51:17 GMT

Dr. Srdjan Acimovic, the new tree fruit pathologist at Virginia Tech’s Winchester Research and Extension Center has asked that I post this message for him. Srdjan wishes to conduct a survey targeting commercial growers of tree fruit and specialty crops in Virginia, which will provide him with their feedback on the economic significance of plant diseases in their individual operations and their opinions about the importance of plant disease research. Dr. Acimovic compiled the questions in this survey, which is intended to help direct and guide his research and extension programs in tree fruit and specialty crop pathology. The survey is anonymous and no personal or specific farm data will be collected. Your participation would be greatly appreciated, and you can do so by clicking on the text below.

Virginia Tree Fruit & Specialty Crop Disease Significance Survey

CM and OFM Degree Days and Optimal Spray Timing, 7.15.21

Chris Bergh — Thu, 15 Jul 2021 12:26:30 GMT

CM and OFM Degree Days and Optimal Spray Timing, 7.12.21

Chris Bergh — Mon, 12 Jul 2021 17:13:01 GMT

Apple Fruit Thinning-Winchester-May 14

S. Sherif — Sat, 15 May 2021 05:15:34 GMT

Our fruit size averages for ‘Gala’, ‘Red Delicious’ and ‘Honeycrisp apples in Winchester are 15.66, 14.9 and 13.23 mm, respectively. If you applied thinning treatments on May 2 or 4, you should be able to see thinning responses by now. Fruitlets to be abscised will be loose and easily pulled off. In order to assess the response of thinning applications applied on May 4, we marked the fruitlets of 10 clusters of Gala, Honeycrisp and Reds and tracked their sizes in the last three days using a digital caliper. The idea behind this was to monitor the fruit growth rate and determine how many fruitlets will eventually abscise. Fruitlets to be abscised are believed to have a growth rate that is less than 50% of the fastest growing fruit on the tree. For instance, the fastest growth rate for Gala in the past three days was 0.6 mm per day. A fruit in the cluster that shows less than 0.3 mm/day will likely abscise soon. Based on this, we have found that our thinning applications on May 4, will result on 50%, 67%, 82% abscission rate for Reds, Gala and Honeycrisp, respectively. On other words, we should expect more triples, doubles and singles/cluster for these three cultivars, respectively. Our per acre thinning rates for Gala and Reds were (64-96 fl oz of Exilis + 1 qt of Sevin + 1 pt of Regulaid). For Honeycrisp, our rate was (4.5 oz of Refine + 1 qt of Sevin + 1 pt of Regulaid). If you applied similar rates on the same day for the same cultivars, your responses will be likely the same.

The Apple Carbohydrate Thinning Model at NEWA.Cornell. For this location (Winchester, VA) I used March 20 and April 16 for the green tip and bloom dates, respectively. Precent flowering spurs (51-75%). The model was run on Saturday May 15 at 1:10 am. Winchester VT AHS AREC weather station was used for this location.

If, after assessing thinning responses in your orchard, you still feel that another thinning application is required, it’s still possible to apply 6-BA and NAA applications until your average fruit sizes are ~ 18 mm. NAA would likely result in better thinning responses at this stage. As shown in the figure below, the carbohydrate model predicts carbohydrate surplus in the next three days and therefore the recommendations are to increase the rate of thinning materials by 30%.

For cultivars exceeding an average fruit size of 20 mm , NAA and 6-BA applications won’t be effective. If more thinning is required, the only chemical option available would be ethephon. You will find more information about rescue thinning by ethephon in the following blog post (https://blogs.ext.vt.edu/tree-fruit-horticulture/2020/05/20/apple-rescue-thinning-by-ethephon/).

Summer disease update

noreply@blogger.com — Tue, 11 Aug 2020 03:25:00 GMT

Six extended wetting events since Jul 22 have dramatically increased summer disease pressures in the Winchester area: Jul 22: 6 hr wetting at 73° with 0.9 in. rain, Jul 23-24: 13 hr wetting at 73° with 0.51 in. rain, Jul 30-31: 21 hr wetting at 70° with 1.01 in. rain; Aug 1-2: 15 hr wetting at 72° with 0.45 in. rain, Aug 3-4: 19 hr wetting at 68° with 0.92 in. rain; and Aug 6: 6 hr wetting at 68° with 0.2 in. rain. Suffice it to say that Winchester's extended dry conditions of July have passed! Wetting events at these temperatures have favored development of sooty blotch and flyspeck and the rot fungi. Evidence of early season (scab), mid-season (Brooks spot), and late season diseases (sooty blotch and developing rots) is shown below:

Scab, sooty blotch and rot spots on unprotected Granny Smith fruit at Virginia Tech AREC, Winchester, VA, Aug 10, 2020.

Infection by Brooks spot (8 o'clock and 1 o'clock positions from the calyx), as well as sooty blotch and rot spots on unprotected Idared fruit, Aug 10, 2020. Infection by Brooks spot, one of the earliest "summer diseases", typically occurs about a month after petal fall.

Recent disease pressure has been somewhat heavier than Winchester in other areas of Virginia, especially east of the Blue Ridge. Amounts of rainfall from extended wetting events have varied, especially with the remnants of the recent hurricane. Most were not excessive in areas where rain was needed; some extended wetting occurred with only a few hundredths of an inch of rainfall. All of these have been favorable for rot development where protection was inadequate and volume of rainfall can impact fungicide residual.

Fire blight-killed shoots harbor the rot fungi and are a common pre-harvest inoculum source. Due to cool temperatures throughout bloom, the Winchester area mostly escaped fire blight this year, but infection was more common east of the Blue Ridge and in the Roanoke area.

Accumulated wetting hours through the summer can be an indicator of summer disease pressure, particularly to predict the development of the sooty blotch and flyspeck (SBFS) fungal complex, but also can be a general indicator of rot pressure. To predict SBFS, we record accumulated wetting hours (ACW) from rainfall, fog, or dew, starting 10 days after petal fall. The action threshold of 250 ACW predicts that the SBFS fungi are present on unprotected fruit when the threshold is reached, and symptoms will soon appear with further incubation. Winchester passed the 250-hr threshold on July 21, and symptoms are now present on unprotected fruit, as shown above, with symptoms heavier at lower elevations, which have more wetting hours. Here is a listing of selected petal fall dates and current total wetting hour accumulation (ACW) for selected locations as of Aug 10: Winchester, May 5, 393 ACW; Staunton, May 5, 823 ACW; Roanoke, Apr 18, 447 ACW; Floyd, Apr 28, 470 ACW; Manassas, Apr 28, 694 ACW; Sperryville, Apr 28, 387 ACW; Crozet, Apr 18, 423 ACW; Carter Mountain, Apr 18, 558 ACW; Red Hill, Apr 18, 483 ACW; Lynchburg, Apr 13, 647 ACW; Rustburg, Apr 13, 573 ACW; Danville, Apr 13, 832 ACW.

Unless unusual fruit disease-related events occur, this will be the final post for this year. With approaching harvest, carefully observe pre-harvest intervals and per acre per year restrictions for all fungicides and all crop protection products.

Bitter rot; sooty blotch, flyspeck threshold and activity

noreply@blogger.com — Wed, 22 Jul 2020 07:41:00 GMT

Conditions have been dry at Winchester, with only three extended wetting events at Winchester in the past month: June 27-28: 9 hr of wetting at 72° with 0.17 in. rain, July 10-11: 6 hr of wetting at 71° with 0.07 in. rain, and July 21-22: more than 10 hr of wetting at 72° with 0.28 in. rain. In spite of the rain received July 21, the Winchester area is still experiencing drought, with July rainfall total at Winchester AREC only 0.49 inches.

Bitter rot (shown below) was observed in a organic production block July 21. This indicates that, although weather has been dry the past month, there was ample opportunity earlier for bitter rot infection which is now evident.

Bitter rot in Honey Crisp apples July 21, 2020. Likely inoculum source was a large overwintering fruit mummy (upper left).

Bitter rot in Honey Crisp apple July 21, 2020. Likely inoculum source was small, current season, fruit mummies (upper left).

Other areas of Virginia have received variable amounts of rainfall in the past month. Some areas have been dry like Winchester, while others have received adequate moisture. Few have had excessive rainfall, but all could have bitter rot conditions as favorable as those in Winchester.

To predict the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (ACW) from rainfall, fog, or dew, starting 10 days after petal fall. The action threshold of 250 ACW predicts that the SBFS fungi are present on unprotected fruit when the threshold is reached, and symptoms will soon appear with further incubation. After several weeks delay, Winchester and Sperryville have now exceeded the 250-hr threshold. Here is a listing of selected petal fall dates and total wetting hour accumulation (ACW) for selected locations as of the night of July 21: Winchester, May 5, 271 ACW; Staunton, May 5, 591 ACW; Roanoke, Apr 18, 423 ACW; Floyd, Apr 28, 342 ACW; Manassas, Apr 28, 461 ACW; Sperryville, Apr 28, 272 ACW; Crozet, Apr 18, 332 ACW; Carter Mountain, Apr 18, 473 ACW; Red Hill, Apr 18, 375 ACW; Lynchburg, Apr 13, 488 ACW; Rustburg, Apr 13, 361 ACW; Danville, Apr 13, 667 ACW.

Extended wetting periods and volumes of rainfall expected to increase sooty blotch/flyspeck and rot pressure

noreply@blogger.com — Mon, 22 Jun 2020 02:14:00 GMT

Three extended wetting events at Winchester in the past week favored secondary apple scab and summer disease development. These occurred June 10-11: 10 hr of wetting at 73° with 0.23 in. rain, June 17-18: 14 hr of wetting at 65° with 0.69 in. rain and June 21: 16 hr of wetting at 65° with 0.01 in. rain. Cedar-apple rust infection on leaves over most of the length of unprotected shoots (shown below) indicates that infection occurred well into June this year, but galls have now been depleted of inoculum at Winchester AREC.

Cedar-apple rust on York Imperial apple shoot June 20, 2020.
Lesions on all but the youngest leaves show that infection occurred well into June.

Apple powdery mildew infection occurs on days without rainfall above 53°, and in the Winchester area we have had 38 days favorable for infection since spores were available on Mar 29.

Other areas of Virginia also received significant wetting events in the past two weeks, June 10-11, and especially June 14-19. Some of these were extremely long wetting periods with heavier rainfall than Winchester: Staunton June 16-19, 51 hr with 1.88 in. of rain; Roanoke three wetting periods June 14-18, totaling 65 hr and 5.75 in. rain; Batesville June 16-19, 44 hr with 1.31 in. rain; Carter Mt., June 15-18, 64 hr with 0.91 in. rain; Red Hill, three wetting periods June 13-19, totaling 54 hr and 0.9 in. rain; Lynchburg, two periods June 15-19, total 76 hr and 3.79 in. rain; Rustburg, June 14-19, two periods totaling 79 hr and 3.81 in. rain; Danville, two periods, total 67 hr and 1.8 in. rain. These long wetting periods and volumes of rainfall should be expected to increase pressure from sooty blotch and flyspeck and various fungal rot diseases.

To predict the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (ACW) from rainfall, fog, or dew, starting 10 days after petal fall. The action threshold of 250 ACW predicts that the SBFS fungi are present on unprotected fruit when the threshold is reached, and symptoms will soon appear with further incubation. All of the monitored areas except Winchester and Sperryville have now exceeded the 250-hr threshold, and Winchester and Sperryville will likely pass the threshold in the next 7-10 days. Here is a listing of selected petal fall date and total wetting hour accumulation (ACW) for selected locations as of June 21: Winchester, May 5, 187 ACW; Staunton, May 5, 324 ACW; Roanoke, Apr 18, 316 ACW; Floyd, Apr 28, 291 ACW; Manassas, Apr 28, 257 ACW; Sperryville, Apr 28, 199 ACW; Batesville, Apr 18, 316 ACW; Crozet, Apr 18, 276 ACW; Carter Mountain, Apr 18, 435 ACW; Red Hill, Apr 18, 291 ACW; Lynchburg, Apr 13, 366 ACW; Rustburg, Apr 13, 361 ACW; Danville, Apr 13, 450 ACW.

Extended wetting events and accumulated wetting hours favor early rot development

noreply@blogger.com — Wed, 10 Jun 2020 03:56:00 GMT

Two extended wetting events at Winchester last week favored secondary apple scab and cedar-apple rust infection and early rot development. These occurred June 4-5: 17 hr of wetting at 69° with 0.83 in. rain and June 5-6: 18 hr of wetting at 69° with 0.42 in. rain. Wetting was variable across other commercial fruit production areas of Virginia. Apple powdery mildew infection occurs on days without rainfall above 53°, and the Winchester area we have had 33 days favorable for infection since spores were available on Mar 29.

To predict the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (ACW) from rainfall or dew, starting 10 days after petal fall. The action threshold for SBFS development is 250 ACW. Here is a listing of selected petal fall date and total wetting hour accumulation (ACW) for selected locations as of June 9: Winchester, May 5, 112 ACW; Staunton, May 5, 217 ACW; Roanoke, Apr 18, 205 ACW; Floyd, Apr 28, 188 ACW; Manassas, Apr 28, 182 ACW; Sperryville, Apr 28, 146 ACW; Batesville, Apr 18, 208 ACW; Crozet, Apr 18, 178 ACW; Carter Mountain, Apr 18, 314 ACW; Red Hill, Apr 18, 189 ACW; Lynchburg, Apr 13, 243 ACW; Rustburg, Apr 13, 247 ACW; Danville, Apr 13, 331 ACW.

ACW is related to wetting from rainfall, fog, or dew. The action threshold of 250 ACW signals that the SBFS fungi would be present on unprotected fruit when the threshold is reached and symptoms would appear with further incubation. Carter Mountain and Danville have passed the threshold, and Lynchburg and Rustburg are close to the threshold.

Extended wetting events and accumulated wetting hours predict the development of sooty blotch and flyspeck

noreply@blogger.com — Tue, 02 Jun 2020 07:37:00 GMT

At Winchester last week a secondary apple scab and cedar-apple rust infection period occurred May 28: 7 hr of combined wetting at 69° with 0.09 in. rain. Most of the other commercial fruit production areas of Virginia experienced similar conditions, with relatively warm extended wetting during the period from May 27 to 29. Expect extended wetting events with warmer temperatures to increase the potential for early latent rot infection of fruit. At Winchester, cedar-apple rust galls remain active. Apple powdery mildew infection occurs on days without rainfall above 53°, and in the Winchester area we have had 29 days favorable for infection since spores were available on Mar 29.

To predict the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (ACW) from rainfall or dew, starting 10 days after petal fall. The action threshold for SBFS development is 250 ACW. Here is a listing of selected petal fall date and total wetting hour accumulation (ACW) for selected locations: Winchester, May 5, 73 ACW; Staunton, May 5, 167 ACW; Roanoke, Apr 18, 194 ACW; Floyd, Apr 28, 174 ACW; Manassas, Apr 28, 131 ACW; Sperryville, Apr 28, 114 ACW; Batesville, Apr 18, 186 ACW; Crozet, Apr 18, 162 ACW; Carter Mountain, Apr 18 329 ACW; Red Hill, Apr 18, 175 ACW; Lynchburg, Apr 13, 226 ACW; Rustburg, Apr 13, 235 ACW; Danville, Apr 13, 288 ACW.

The action threshold of 250 ACW signals that the SBFS fungi would be present on unprotected fruit when the threshold is reached and symptoms would appear with further incubation. Carter Mountain and Danville have already passed the threshold, and Lynchburg and Rustburg may reach the threshold within the coming week . ACW is related to wetting from rainfall or dew, and typically, lower elevations in an orchard accumulate wetting hours more quickly because of wetting from dew. So far this year, that was not the case with the higher elevation of Carter Mountain accumulating wetting hours more rapidly from extended wetting from rainfall and fog in the past two weeks.

Extended wetting last week will trigger early summer disease development

noreply@blogger.com — Tue, 26 May 2020 08:28:00 GMT

At the AREC last week an apple scab and cedar-apple rust infection period occurred May 22-23: 24 hr of combined wetting at 60° with 1.14 in. rain. Conditions were similar east of the Blue Ridge in Manassas and Sperryville, but more extreme to the south from Staunton to Roanoke and Floyd and east of the Blue Ridge from the Charlottesville area southward to Lynchburg and Danville. At Winchester, cedar-apple rust galls remain active with more extended wetting periods predicted for this week.

Staunton had two wetting periods of 10 and 42 hr with a total of 0.91 in. rain. In Roanoke, two infection periods totaled 113 hr combined wetting and 10.17 in. rain. The total rainfall in Floyd was 1.92 inches, but with 115 hr of extended wetting. In Albemarle County, combined wetting ranged from 43-55 hr at Crozet, Red Hill and Batesville to 102 hr on Carter Mountain with rainfall totals from 1.3 to 2.6 inches. Lynchburg had 86 hr wetting with 2.95 in rain, Rustburg 114 hr wet with 3.87 in. rain and Danville 89 hr combined wetting with 4.69 in. rain.

In all areas, this extended wetting will contribute to early accumulation of wetting hour totals toward development of sooty blotch and flyspeck. Fortunately, much of the earlier portion of the wetting events was at cooler temperatures not as favorable to rot development, but the latter portion was at warmer temperatures, and occurred after heavy rains would have depleted fungicide residue, making the fruit vulnerable to latent rot infection. This extended wetting was also favorable to secondary scab and late rust infection on foliage, and the extremely long wetting periods can increase the amount of fruit scab.

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (ACW) from rainfall or dew, starting 10 days after petal fall. The action threshold for SBFS development is 250 ACW. Here is a listing of selected petal fall date and total wetting hour accumulation (ACW) for selected locations: Winchester, May 5, 55 ACW; Staunton, May 5, 133 ACW; Roanoke, Apr 18, 174 ACW; Floyd, Apr 28, 159 ACW; Manassas, Apr 28, 91 ACW; Sperryville Apr 28, 102 ACW; Batesville Apr 18, 164 ACW; Crozet, Apr 18, 138 ACW; Carter Mountain, Apr 18 329 ACW; Red Hill, Apr 18, 150 ACW; Lynchburg, Apr 13, 199 ACW; Rustburg, Apr 13, 201 ACW; Danville, Apr 13, 243 ACW. The action threshold of 250 ACW means that the SBFS fungi would be present on unprotected fruit when the threshold is reached. Lynchburg, Rustburg and Danville are predicted to reach the threshold within the coming week and Carter Mountain has already passed the threshold. ACW is related to wetting from rainfall or dew, and often lower elevations in an orchard accumulate wetting hours more quickly because of wetting from dew, but that obviously is not the case with the higher elevation of Carter Mountain this year.

Apple powdery mildew infection occurs on days without rainfall above 53°, and in the Winchester area we have had 26 days favorable for infection since spores were available on Mar 29.

Fire blight infection conditions on late bloom May 15; scab and rust infection May 14-15.

noreply@blogger.com — Tue, 19 May 2020 07:12:00 GMT

Fire blight infection conditions finally occurred at Winchester on late bloom May 15. Below is a cropped graphic from the Maryblyt 7 program.

Graphic from Maryblyt 7, May 18, 2020. Click to enlarge.

While most apple blocks were past bloom in the Winchester area, a few still had some susceptible bloom. The temperature and rainfall data are current through Monday evening, May 18. Predicted weather conditions are shown for May 19-31. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, and this must coincide with an average daily temperature of 60°F or more. Based on recorded temperatures and wetting, the risk column shows the infection was possible wherever bloom was present May 15. Infection aslo would have been possible with wetting May 16-17. The extended outlook through May 31 is shown primarily to track infection development from May 15, but indicates that infection would be possible wherever there is bloom and wetting May 27-31.

The BBS column tracks the appearance of blossom blight symptoms from infection that occurred May 15, which is now predicted for May 27. The CBS column tracks canker blight symptom appearance and predicted canker margin symptoms (CMS, expansion of overwintered cankers) May 16. Further tracking in the CBS column predicts canker blight symptoms when that value reaches 100 May 28.

Under these conditions a Streptomycin application would have been recommended for May 14-15, to protect any late bloom through the infective period. This would particularly include any young and recently planted trees with flowers. Cooler predicted temperatures the next week indicate a decline in risk, but warmer temperatures will again bring the EIP to an infective level May 26. Note that "wetting" can occur with maintenance and thinning applications, so streptomycin should be included in such applications if there is late bloom. Also note that, while bloom may have escaped infection during this unusually low fire blight pressure year at Winchester, expect canker blight and shoot blight symptoms if cankers were allowed to overwinter in trees that had infection last year.

At the AREC last week an apple scab and cedar-apple rust infection period occurred May 14-15: 8 hr wet at 62° with 0.04 in. rain. Similar conditions also extended south to Staunton and east of the Blue Ridge from Manassas to Sperryville. Staunton and Sperryville to the Charlottesville area also had an infection period May 17. At Winchester, cedar-apple rust galls remain active after this wetting event with only 0.04 inches of rain.

Apple powdery mildew infection occurs on days without rainfall above 53°, and in the Winchester area we have had 16 days favorable for infection since spores were available on Mar 29. Secondary mildew symptoms are now quite common on unprotected trees, as are secondary scab and cedar-apple rust lesions.

Extended wetting is predicted for all major fruit production areas in Virginia May 18-22. This wetting will be highly favorable to secondary scab and late rust infection on foliage and will contribute to recorded accumulated wetting hours for development of sooty blotch and flyspeck (SBFS). For purposes of predicting the development of the SBFS fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we will use May 5 as the petal fall date for Winchester, so the start of wetting hour accumulation (ACW) will be from May 15. For the Roanoke area and areas east of the Blue Ridge, we will consider petal fall to have been one week earlier than Winchester, and accumulation of wetting hours will be from May 8. The action threshold for SBFS development is 250 ACW.

Secondary scab infection May 5-6; fire blight infection conditions on late bloom May 15-18.

noreply@blogger.com — Tue, 12 May 2020 07:04:00 GMT

At Winchester, most apple varieties are well beyond petal fall, but late bloom susceptible to fire blight persists on some late varieties and some recently planted trees.

At the AREC last week an apple scab infection period occurred May 5-6: 17 hr wet at 47° with 0.18 in. rain. Similar conditions also extended south to Staunton and east of the Blue Ridge from Loudoun County to the Charlottesville area, where infection conditions resulted from a combined wetting period. At Winchester, cedar-apple rust galls and quince rust cankers remain active after this wetting event.

Apple powdery mildew infection occurs on days without rainfall above 53°, and we have had 14 days favorable for infection since spores were available on Mar 29. Below is an example of primary and secondary powdery mildew on Idared apple.

A secondary powdery mildew lesion (bottom left) next to a primary mildew shoot on Idared apple.

The Winchester area will likely see its first fire blight infection conditions wherever susceptible bloom remains this weekend, May 16-18. Similar conditions exist for all other major fruit producing areas of Virginia, but with some starting on May 15. Blossom infection has already been reported on apples east of the Blue Ridge south of Charlottesville and in southwest Virginia, and on pears in Clarke County from infection that occurred six weeks ago. Below is an example of late bloom that was observed on Goldrush apple in Nelson County last week.

Late bloom and set fruit on Goldrush apple in Nelson County May 7, 2020.

Just to add a footnote about the unusually cool conditions through April and into mid-May that allowed the Winchester area to escape fire blight infection from Mar 30 until the very latest of bloom: The daily mean high temperature for April this year was 60.0° and, since 1928 only three years had a cooler mean daily high temperature, 1935, 1961, and 1966! Meanwhile, 17 years had a mean April high greater than 70°

Secondary apple scab and rust infection periods April 28 through May 4; fire blight pressure low to moderate in the Winchester area

noreply@blogger.com — Tue, 05 May 2020 06:39:00 GMT

At Winchester, most apple trees are at petal fall and only later varieties such as Rome Beauty and some young trees are still in bloom.

At the AREC in the past week we received three apple scab/rust infection periods. Apr 28: 9 hr wet at 49° with 0.06 in. rain; Apr 29-30: 19 hr wet at 58° with 1.22 in. rain (heavy scab and rusts) and May 3-4: 7 hr wet at 62° with 0.42 in. rain. Cedar-apple rust galls and quince rust cankers remain active after these wetting events, and unprotected apple blossoms and small fruit remain susceptible to quince rust infection, so a follow-up application including an SI fungicide is suggested. On May 4 cedar rust lesions were evident on flower cluster and shoot leaves, from infection that occurred Apr 7-8.

This past week the length of wetting and amounts of rainfall have been somewhat variable across the major commercial fruit production areas of Virginia, but all areas received at least one extended wetting period favorable to secondary scab infection where control was not achieved during earlier primary infection periods.

Apple powdery mildew infection occurs on days without rainfall above 53°, and we have had 12 days favorable for infection since spores were available on Mar 29. Expect secondary powdery mildew symptoms to begin appearing in the next week or so.

In the Winchester area, fire blight pressure has been mostly low to moderate on apples that first bloomed Mar 30, and that trend continues for late blooming apples through the coming week, However, fire blight blossom symptoms were reported on early blooming Asian pears Apr 27 in Clarke County. Also blossom infection (shown below) was also evident in young apple trees in central Virginia, apparently from infection that occurred Mar 29.

Blossom blight symptoms in central VA, May 2, 2020. Infection probably occurred Mar 29.

Apple scab and rust infection Apr 23-27; fire blight blossom symptoms reported on early blooming Asian pears in Clarke Co.

noreply@blogger.com — Tue, 28 Apr 2020 07:46:00 GMT

At Winchester, Red Delicious apple trees are near petal fall, but there is still much bloom on many apples, and later varieties such as Rome Beauty are now in full bloom. At the AREC we received two recent infection periods. Apr 23-24: 21 hr wet at 50° with 0.41 in. rain (scab and rusts); Apr 25-27: 31 combined hr wet at 47° with 0.80 in. rain. Cedar-apple rust galls and quince rust cankers were in "full bloom" during these extended wetting events, and unprotected apple blossoms remain very susceptible to quince rust infection, so a follow-up application including an SI fungicide is suggested. On Apr 27 a few cedar rust lesions were evident on flower cluster leaves, from infection that occurred Mar 27-28.

The above conditions for Winchester were generally similar across most of the major commercial fruit production areas of Virginia. The greatest concerns for these events are where earlier infection periods occurred with inadequate fungicide protection, and scab lesions are now sporulating, leading to heavy secondary infection.

Apple powdery mildew infection occurs on days without rainfall above 53°, and we have had ten days favorable for infection since spores were available on Mar 29. Expect secondary powdery mildew symptoms to begin appearing in the next week or so.

Although fire blight pressure has been mostly low to moderate on apples that first bloomed Mar 30 in the Winchester area, fire blight blossom symptoms on early blooming Asian pears were reported Apr 27 in Clarke County. In that case, apparently the pear trees were in bloom by Mar 19 and infection likely occurred on Mar 20, before the first apple blossoms were open at our AREC.

Fire blight pressure low to moderate through April 25; secondary scab infection possible where control was inadequate Mar 27-28.

noreply@blogger.com — Tue, 21 Apr 2020 06:06:00 GMT

At Winchester apple trees are mostly at mid-bloom.

Fire blight: With prevailing cool temperatures, current fire blight pressure remains low to moderate through Apr 25 in the Winchester area, the Shenandoah Valley, and across much of northern Virginia. Conditions through Apr 25 are not favorable for fire blight infection in the Roanoke and east of the Blue Ridge south of Charlottesville, however some of these areas had earlier potential infection Mar 28-31 and Apr 7-9.

Scab: At the AREC we received a marginal apple scab infection period Apr 17-18: 14 hr wet at 47° with 0.08 in. rain. Most of the scab ascospores have been discharged signalling the end of the primary infection, but where protection was inadequate during the Mar 27-28 infection period, expect lesions to be appearing, and secondary infection could be possible with predicted wetting events later this week.

At Winchester, we have had 12 days favorable for apple powdery mildew infection since spores were available.

This will be updated again Apr 28.

Apple scab and rust infection April 12-13; fire blight pressure low to moderate through April 19.

noreply@blogger.com — Tue, 14 Apr 2020 08:10:00 GMT

At Winchester apple trees are mostly at mid-bloom, with later cultivars coming into bloom.

At the AREC we received an apple scab, quince rust and cedar-apple rust infection period Apr 12-13 with 15 hr wet at 57° with 0.74 in. rain. Earlier last week we also had a possible combined scab/rust infection period Apr 7-8 with 9 hr wetting at 57° with 0.94 in. rain. More than 95% of the scab ascospores are now mature in the Winchester area. At Winchester, we have had 10 days favorable for apple powdery mildew infection since spores were available.

Most of the commercial fruit production areas in Virginia had similar scab and rust infection conditions Apr 12-13, but with more rainfall east of the Blue Ridge and southward. Rainfall ranged from 1.5 inches at Sperryville and 2.3 inches at Manassas to 3.36 inches at Lynchburg. Such volumes of rainfall deplete fungicide protection, calling for fungicides with after-infection control for scab and rusts, as well as something for protection against powdery mildew in mildew-susceptible cultivars..

FIRE BLIGHT: With most apples in bloom, the current fire blight threat remains moderate to low in the Winchester area.

Graphic from Cougarblight, April 14, 2020. Click to enlarge.

Above is the graphic from the Cougarblight model as shown on our NEWA site. We selected orchard blight history option as “Fire blight occurred in your neighborhood last year” and first blossom open date as 3/30/20. Cougarblight shows color-coded risk assessment as “Cougarblight 4-Day DH” risk is moderate or low through Apr 19. The Roanoke area and areas east of the Blue Ridge south of Charlottesville had possible infection Apr 7-9 (graphics not shown), and after high risk Apr 13, are now also showing moderate to low infection potential through Apr 19.

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations.

This week's fire blight outlook for Winchester and beyond

noreply@blogger.com — Mon, 06 Apr 2020 07:40:00 GMT

NOTE: This year for fire blight risk assessment, I will post a graphic from the Cougarblight model as shown on our NEWA site. I will be using the same weather data from our NEWA station to make a comparison to Maryblyt 7 as in previous years, but not posting the MaryBlyt graphic. We thank Dr. Mizuho Nita for hosting the Maryblyt 7.1 download site at: http://grapepathology.org/maryblyt

Graphic from Cougarblight, April 6, 2020. Click to enlarge.

FIRE BLIGHT: Above is the graphic from the Cougarblight model as shown on our NEWA site. We selected orchard blight history option as “Fire blight occurred in your neighborhood last year” and first blossom open date as 3/30/20. Cougarblight shows color-coded risk assessment as “Cougarblight 4-Day DH” risk is low or caution for this week Apr 7-11. The Roanoke area and areas east of the Blue Ridge south of Charlottesville have a potential for infection Apr 7-9 (graphics not shown). Setting the first bloom date to 3/25/20 instead of 3/30/20 did not make any difference in prediction of infection for this week. However, Roanoke and areas south of Charlottesville could have had earlier infection (March 27-31) if the first bloom date had been as early as March 20.

Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection, which occurs with wetting. The fire blight outlook will be updated Apr 13.

Apple scab infection March 27-28; powdery mildew infection Mar 29-30

noreply@blogger.com — Tue, 31 Mar 2020 03:58:00 GMT

At Winchester we are seeing mostly pink stage, with a few early blossoms open on Idared and Pink Lady apples. At the AREC we received our first definite apple scab infection period Mar 27-28 with 15 hr wet at 53° with 0.57 in. rain. More than half of the scab ascospores are now mature in the Winchester area. Only a few cedar-apple rust spores were discharged during the recent wetting, but spore horns are now fully mature. Apple powdery mildew spores are available, and infection could have occurred on Mar 29 and 30.

As shown below, a few early apple and crabapple blossoms were open Mar 30. However, with cool temperatures predicted most of the next two weeks, the current fire blight threat is minimal in the Winchester area.

Early bloom on Idared apple, March 30, 2020. Winchester, VA.

Early season apple disease activity

noreply@blogger.com — Mon, 23 Mar 2020 00:44:00 GMT

Due to other pressing commitments this year, some of my updates and bud development stages may be delayed. Every orchardist should be aware of ongoing developments in their own orchard and protect or react accordingly. The updates for the Winchester area are based on the AREC's NEWA weather station as they have been since 2017. This resource and other NEWA stations in Virginia are available publicly, and all growers and advisers should be using them in their disease management decisions.

Tight cluster stage on Red Delicious at Virginia Tech AREC, Winchester. Note the small mummified blossom next to the developing flower cluster. These and dead twigs are a common source for spores of fruit rot and frogeye leaf spot fungi.

Apple scab outlook: At Winchester on Sunday March 22, we are seeing tight cluster stage on Red Delicious and other advanced cultivars. Because of potential for fruit russet, this stage is too late for application of copper sprays to fresh market fruit, and another protectant fungicide should be used ahead of infection. With green tip set at March 7, the apple scab program on our AREC NEWA station indicates that 17% of the scab ascospores have matured, and many would be ready for a potential infection period with combined wetting over the next several days or later in the week. This is a high level of ascospore maturity for the first infection period of the year and could result in heavy primary infection on the large susceptible target.

Where there is concern that scab infection may have occurred without any fungicide protection, it would be prudent to mix Vangard (cyprodinil) with a protectant to improve post-infection control. Dodine (Syllit) is another early season option where scab may be the only apple disease of concern up to pink stage. Do not use Syllit after pink stage.

Expect powdery mildew and rust activity soon in orchards prone to these disease problems.

For the Roanoke area and areas east of the Blue Ridge, please check NEWA stations in your region, adjust your green tip stage setting and hit 'calculate' to predict scab status in your area. Generally, these areas have higher percent ascospore maturity and had their first infection period last week if green tip was present by March 1. The Gadino Cellars NEWA station in Rappahannock County indicates that scab infection could have occurred as early as March 2-3 if green tip was present by March 1.

Summer diseases and powdery mildew; Pre-harvest apple disease outlook in the Winchester area

noreply@blogger.com — Thu, 15 Aug 2019 03:30:00 GMT

In the past month we recorded only two major extended wetting events at our AREC in Winchester: Jul 22-23 (18 hr wet at 68° with 2.74 in. rain) and yesterday, Aug 13-14 (14 hr wet at 72° with 0.5 in. rain). However, there were also nine other wetting events less than 5 hr in length, with relatively small amounts of rainfall, and some of those may have had greater amounts of rainfall and stayed wet longer in surrounding areas.

Due to comparatively delayed wetting hour accumulation this year, sooty blotch was slower to make its appearance, and was first observed at our AREC last week (shown below).

Sooty blotch (and scab) observed on unprotected Fuji apples August 8, 2019.

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we chose May 2 as the petal fall date for Winchester, so the start of wetting hour accumulation (ACW) was from May 12. As of Aug 14, total wetting hour accumulation by our AREC NEWA weather station was 342 hr and the 250-hr action threshold was reached Jul 11. In 2017 by Aug 14 we had recorded 462 ACW, the threshold was reached July 5 and SBFS was observed July 7. By contrast, during the extremely wet year last year (2018), we saw 630 ACW by Aug 14, the 250-hr threshold was reached June 12, and SBFS was observed by June 27.

In trees not protected by fungicides this year, bitter rot is more common than SBFS, indicative of early summer disease pressure in May and June.

Powdery mildew on late shoot growth: As frequently occurs following heavy rains after a dry period, the 2.7 inches of rain Jul 22-23, promoted a flush of renewed late season growth that was very susceptible to mildew (see below).

Powdery mildew on late season growth, Granny Smith apple, July 31, 2019

Late infection often leads to a lot of mildew carryover in buds, and a recurrent problem and a significant reduction in yield the next year. This is particularly true with very susceptible varieties like Granny Smith, Idared, Ginger Gold and Honeycrisp, and in situations like this, it is prudent to select late-season fungicides with mildew activity as well as rot and SBFS activity. Examples include products such as Merivon, Luna Sensation, Pristine, Inspire Super and Indar. Caution: Remember to observe allowed pre-harvest intervals for all fungicides as well as insecticides and other products.

Increasing summer disease pressures

noreply@blogger.com — Wed, 17 Jul 2019 03:30:00 GMT

Summer disease pressures have increased in the past two weeks. At our AREC in Winchester, we recorded three extended wetting events since the last post Jul 6: Jul 5-6 (13 hr wet at 73° with 0.06 in. rain; Jul 8 (7 hr wet at 73° with 0.12 in. rain); and Jul 11 (8 hr wet at 79° with 0.63 in. rain). Infection by the bitter rot and white rot fungi will occur quickly with wetting and temperatures in the 70s.

The image below, sent to me from the Winchester area, suggests increasing rot pressures.

Rots with mummies. (Photo by W. Mackintosh).

The proximity and distribution of the spots to the mummies suggests that they are developing rots. Some spots were described as having droplets on them. The explanation is that it is probably droplets splashed off the mummies, carrying spores and other dark juicy material. Some droplets carrying spores may incite rot infection and others may not, or some might stay latent for a period of time. Some rots might just be growing slower than others so they get over run by the faster growing organism.

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we chose May 2 as the petal fall date for Winchester, so the start of wetting hour accumulation (ACW) was from May 12. Wetting hour accumulation in July has brought the total ACW to 273 hr, (past the 250-hr action threshold). ACW at Roanoke remains similar to Winchester at 269 hr, but with only 0.36 in. rainfall in July.

Other areas of Virginia with (ACW total) and rainfall in July are: Staunton (452 hr, 1.40 in.); Rappahannock County (Gadino Cellars, 362 hr, 3.06 in. rain); Red Hill (878 hr, 0.24 in.); Lynchburg (552 hr, 1.54 in,); Floyd (362 hr, 1.66 in.); Danville (649 hr, 2.53 in. rainfall).

Variable summer disease pressures

noreply@blogger.com — Sat, 06 Jul 2019 07:01:00 GMT

Summer disease pressures the past month have been generally lighter at Winchester than in other parts of Virginia. For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we chose May 2 as the petal fall date for Winchester, so the start of wetting hour accumulation (ACW) was from May 12. Wetting hours accumulated quite rapidly in May, but more slowly in late June and early July; however, rains the past two days have brought the total ACW (234 hrs) approaching the 250 hr threshold with more rain expected through the weekend. ACW is similar to Winchester at Roanoke (239 hr).

Other areas of Virginia generally had more rainfall than Winchester and more wetting hours in June. Examples, with ACW totals, are: Staunton (377 hr); Rappahannock County (Gadino Cellars) 319; Red Hill (733 hr); Lynchburg (480 hr); Floyd (331 hr); Danville (548 hr).

At our AREC in Winchester we recorded only three extended wetting events since the posts early last month: Jun 13 (10 hr wet at 59° with 0.19 in. rain; Jun 24 (9 hr wet at 74° with 0.54 in. rain); and Jul 4-5 (16 hr wet at 70° with 0.74 in. rain). Other local areas experienced thunderstorms which resulted in more total rainfall and, especially where those occurred in the evening, more ACW.

Summer disease activity

noreply@blogger.com — Wed, 12 Jun 2019 07:55:00 GMT

At our AREC in Winchester we recorded an extended wetting event: Jun 9-10, with 30 hr of wetting at 63° with 0.62 in. rain. This wetting favored development of secondary apple scab, early summer disease activity on apples, peach scab, cherry leaf spot and brown rot on ripening cherries.

Other areas of Virginia generally had more rainfall and longer wetting in the past week with these examples: Rappahannock County (Gadino Cellars) 30 hr wet at 63° with 1.84 in. rain; Red Hill (Jun 7-11, 67 hr wet at 62-70° with 3.5 in. rain); Lynchburg (Jun 7-11, 53 hr wet at 63° with 2.35 in. rain); Roanoke (Jun 6-10, 63 hr wet at 68° with 4.39 in. rain); Floyd (Jun 6-11, 90 hr wet at 63° with 3.25 in. rain); Danville (Jun 6-9, 55 hr wet at 70° with 2.47 in. rain). Heavy amounts of rainfall and lengthy wetting periods at warm temperatures are favorable for Glomerella leaf spot and bitter rot and other fruit rots as well as sooty blotch and flyspeck.

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we chose May 2 as our petal fall date for Winchester, so the start of wetting hour accumulation was from May 12. As of Jun 11, accumulated 147 wetting hours (ACW) toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex at our AREC NEWA station, 932 ft elevation. (Last week I had noted that at a lower elevation, 909 ft, we had already accumulated 331 hr ACW, but that figure was distorted because the wetness sensor had come loose from its stand and dropped into the grass where it remained wet abnormally long).

Most other areas of Virginia have accumulated more wetting hours than Winchester, based on approximate petal fall dates and increased length of wetting in these areas: Rappahannock County (Gadino Cellars) 199 hr; Red Hill 472 hr; Lynchburg, 319 hr; Roanoke, 172 hr; Floyd 220 hr; Danville, 364 hr. Note that the values shown in bold font have passed the 250 wetting hour threshold. This means that the SBFS fungi are now present on unprotected fruit, and would develop symptoms if samples were taken and incubated under moist/humid conditions. Specific protection against SBFS and the rots is recommended at this time.

Peach brown rot: The 3-week period leading up to harvest for individual peach varieties and other stone fruits is a critical time for protection from brown rot. Weather conditions, especially rainfall, will affect how much rot appears on varieties as they ripen. During this period, step up the program to include fungicides specifically active against brown rot. Include Captan with those classes of chemistry that are at risk for development of resistance and rotate chemical classes in the final applications. Application interval should be about 3 weeks and 1 week to harvest for ‘normal’ conditions, but might need to be shortened to offset frequent, heavy rainfall.

Recent extended wetting; early summer disease pressures June 2, 2019

noreply@blogger.com — Mon, 03 Jun 2019 03:35:00 GMT

At our AREC in Winchester we recorded two extended wetting events: May 26-27, with 6 hr of wetting at 69° with 0.15 in. rain; and June 2, with 9 hr of wetting at 61° with 0.2 in. rain. Again these extended wetting events at relatively warm temperatures favored secondary apple scab, early summer disease activity on apples, peach scab, cherry leaf spot and brown rot on ripening cherries.

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we chose May 2 as our petal fall date for Winchester, so the start of wetting hour accumulation was from May 12. As of 8 AM June 2, accumulated wetting hours (ACW) already passed the 250 wetting hour threshold for specific treatment against the SBFS fungal complex: at 909 ft elevation we had 331 hr; at 932 ft (the AREC NEWA station), 93 hr; and at the 983 ft elevation, 90 hr ACW. One of the purposes of following three weather stations is to compare wetting hour accumulation at different elevations. Note that we have already passed the threshold at the lower elevation and the total is more than 100 hr ACW more than last year on this date. At the two higher elevations ACW accumulation is more than 100 less than last year at this time. NOTE: Edited Jun 12: Last week we discovered an error with the sensor at the lower elevation, 909 ft, which had already accumulated 331 hr ACW; that figure was distorted because the wetness sensor had come loose from its stand and dropped into the grass where it remained wet abnormally long.

The sooty blotch/flyspeck model on NEWA indicates accumulated wetting similar to the ACW shown at our NEWA station. To use this model, select a weather station, go to the drop-down menu for diseases and enter the petal fall date (e. g. May 2) to calculate the risk for that location.

Sooty blotch/flyspeck risk summary for Winchester AREC, 932 ft elevation, using May 2 as petal fall date.

For central Virginia, we selected Apr 23 as the petal fall date for accumulation of wetting hours by selected weather stations. As of June 2, Red Hill had 349 ACW (also past the threshold). Lynchburg had 240 ACW. Also east of the Blue Ridge, the NEWA station at Batesville has 109 ACW, while the NEWA station at Gadino Cellars near Washington, VA has recorded 150 ACW with Apr 29 as the petal fall date.

Heavy scab infection period May 10-12.

noreply@blogger.com — Wed, 15 May 2019 05:51:00 GMT

We recorded another heavy combined apple scab infection period at Winchester over this past weekend: May 10-13 (47 combined hr wet at 53° with 1.44 inches of rain). Scab lesions have been observed on unprotected trees in the Winchester area. A follow-up fungicide application with after-infection scab activity is suggested. Cedar-apple rust gall inoculum is now mostly depleted.

Also, we have had 20 days favorable for powdery mildew infection since spores were available at Winchester Apr 6.

Heavy scab and rust infection, May 3-6

noreply@blogger.com — Mon, 06 May 2019 08:02:00 GMT

We recorded two heavy apple scab and rust infection periods at Winchester over the weekend: May 3-4 (19 hr wet at 64° with 0.4 inches of rain) and May 4-5 (more than 21 hr wet at 62° with 2.18 inches of rain). The last wetting period, with heavy rainfall, is still in progress. This amount of rainfall depleted any fungicide residue applied last week, resulting in potentially heavy rust and scab infection to foliage and fruit. A follow-up fungicide application with after-infection activity is suggested.

Also, we have had 18 days favorable for powdery mildew infection since spores were available at Winchester Apr 6. The fire blight outlook for Winchester remains much as indicated in the post on May 2: the risk of infection remains high wherever there is late bloom present.

Fire blight outlook into next week

noreply@blogger.com — Thu, 02 May 2019 04:39:00 GMT

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Fruit producers in other areas are encouraged to consult their state extension specialists for information similar to that provided here.

Graphic from Maryblyt 7, May 1, 2019. Click to enlarge.

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. We have moved through bloom in a timely fashion in the Winchester area, but many apple blocks still have some susceptible bloom. The temperature and rainfall data are current through Wednesday evening, May 1. Predicted weather conditions are shown for May 2-6. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, and this must coincide with an average daily temperature of 60°F or more. Based on recorded temperatures and wetting, the risk column shows the infection was possible Apr 19 and 25, and was possible with wetting Apr 18, 23 and 24, and will again be possible with wetting May 2-4. The temperature is marginally close for infection May 5. The extended outlook May 6 through May 10 (not shown) indicates infection is possible wherever there is bloom and wetting through May 10.

Streptomycin application is recommended for tomorrow, May 2, to protect any late bloom into the weekend. Also, remember to protect any young and recently planted trees that have flowers. Predicted temperatures into next week (not shown) indicate that infection will remain possible wherever there is late bloom and wetting every day next week. Note that "wetting" can occur with maintenance and thinning applications, so streptomycin should be included in such applications where there is late bloom.
The BBS column tracks the appearance of blossom blight symptoms from infection that occurred Apr 19, which is now predicted for May 3. The CBS column is tracking canker blight symptom appearance and predicts canker margin symptoms (CMS, expansion of overwintered cankers) is predicted May 1. Further tracking in the CBS column will predict canker blight symptoms when that value reaches 100.

Below is the graphic from the Cougarblight model as shown on our NEWA site. with “Fire blight occurred in your neighborhood last year” selected as the orchard blight history option and first blossom open date as 4/13/2019. Cougarblight shows color-coded risk assessments as “Cougarblight 4-Day DH” and infection potential EIP value. This risk is "extreme" for May 2-6, with infection possible if wetting occurs May 2-4. The average temperature of 60 F is lacking for May 5.

Graphic from the NEWA/Cougarblight model, May 1, 2019. Click to enlarge.

Fire blight risks can change quickly with warmer than predicted temperatures and wetting; in high-risk situations, a streptomycin application is more effective when applied ahead of predicted infection. Unless unexpected weather conditions arise, this will be the last fire blight update for this season.

Fire blight outlook Apr 29-May 4; secondary scab infection Apr 27-28.

noreply@blogger.com — Mon, 29 Apr 2019 07:36:00 GMT

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Fruit producers in other areas are encouraged to consult their state extension specialists for information similar to that provided here.

Graphic from Maryblyt 7, April 29, 2019. Click to enlarge.

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Most apple trees still have susceptible bloom in the Winchester area. The temperature and rainfall data are current through Sunday evening, April 28. Predicted weather conditions are shown for April 29-May 4. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, and this must coincide with an average daily temperature of 60°F or more. Based on recorded temperatures and wetting, the risk column shows the infection was possible Apr 19 and 25, and would be possible with wetting Apr 18, 23 and 24, and will again be possible with wetting May 1-4.
Streptomycin application is recommended for tomorrow, Apr 30 or Wednesday, May 1 to protect late bloom into the weekend. Also, remember to protect any young and recently planted trees that have flowers. Predicted temperatures into next week (not shown) indicate that infection will remain possible wherever there is late bloom and wetting every day next week. Note that "wetting" can occur with maintenance and thinning applications, so streptomycin should be included in such applications while late bloom is present. The BBS column tracks the appearance of blossom blight symptoms from infection that occurred Apr 19, which is predicted for May 2. The CBS column is tracking canker blight symptom appearance and predicts canker margin symptoms (CMS, expansion of overwintered cankers) is predicted Apr 30.

Graphic from the NEWA/Cougarblight model, April 29, 2019. Click to enlarge.

Note that real fire blight risks can change quickly with warmer than predicted temperatures and wetting and, in high-risk situations, a streptomycin application is more effective when applied ahead of predicted infection.

We recorded a secondary apple scab infection period at Winchester Apr 27-28: 13 hr wet at 50° with 0.16 inches of rain. This would have been a secondary infection period where scab was not well controlled during the Apr 5-6 infection, resulting in scab lesions with spores now available for secondary infection.

Scab and rust infection Apr 25-26

noreply@blogger.com — Sat, 27 Apr 2019 07:58:00 GMT

We recorded a apple scab and rust infection period at Winchester Apr 25-26: 14 hr wet at 57° with 0.13 inches of rain. This was also an infection period in central Virginia and could have been a secondary infection period where scab was not well controlled during the Apr 5-6 infection, resulting in scab lesions with spores now available for secondary infection. Cedar-apple rust lesions are now visible from the infection period Apr 7-8.

Also, we have had 14 days favorable for powdery mildew infection since mildew spores were available at Winchester Apr 6.