Tag Archives: Central Virginia

Hard Freeze is Expected This Tuesday (March 29)

Posted on March 27, 2022 by S. Sherif

Based on the weather forecast for Tuesday, March 29, temperatures will drop to 19 ^oF for a couple of hours (6:00 – 8:00 am) in the Frederick County and Rappahannock-Madison area, which could be devastating for the majority of apple cultivars and some early-bloom peach cultivars grown in these locations. Our apple cultivars in Winchester are currently in the tight-cluster stage, and some (e.g. Pink Lady and Zestar) are in the full pink-stage now. The majority of peach cultivars are in the pink stage now, with some early-blooming cultivars (e.g. John Boy) are already in bloom. Sweet cherries, on the other hand, are still in tight-cluster stage. Based on the critical temperature tables below, 90% of apple buds at tight-cluster can be killed if exposed to temperatures at 21^oF and below for more than 30 min. Similarly, peach flowers at full bloom can be killed at the temperatures forecasted for Tuesday. Sweet cherry cultivars that are still in tight cluster will be likely OK, and only 10% can be damaged by this freeze event.

This is a typical advective freeze, accompanied by wind > 5 mph and dry air. Unfortunately, none of our frost mitigation measures, e.g., wind machines, overhead and under-tree sprinklers, can be of utility with this type of frost. Using any sprinklers, or spraying the tree with water using an air-blast or any other sprayer, will cause more damage than benefit. Heaters, on the other hand, can provide some protection if used for several hours, probably starting from midnight.

Tree fruit growers in the Nelson County may also face a brief, less damaging frost event, with the lowest temperature predicted to reach 24 ^oF before sunrise. Based on the current forecast, no frost/freeze is predicted for Roanoke and Carroll-Patrick counties.

Accede: a new chemical thinning material for apples and peaches

Posted on March 20, 2022 by S. Sherif

Accede is a new thinning product from Valent BioSciences that you may need to consider for apple fruit thinning and peach blossom thinning. The active ingredient of this product is ACC (1-aminocyclopropanecarboxylic acid (ACC); a chemical that is produced naturally in plant as a precursor for ethylene (the ripening hormone). Unlike other ethylene-based products (e.g. ethephon), Accede doesn’t cause gummosis in peach and nectarine; and is not as aggressive when thinning apples.

For apple fruit thinning: Accede can be used when the king fruit’s average fruit size ranges from 8-25 mm. However, this product is mainly intended for later thinning treatments (fruit size 15-18mm) when the primary thinning materials (e.g. 6-BA and NAA) are no longer effective. This product should be applied at a 23-46 fl oz/acre rate. A reduced rate should be considered if the temp on the day of application is >90 ^oF, and the best results are achieved under slow drying conditions (e.g., early morning, at night).

For peaches and nectarines: Accede is the only labeled chemical thinning product. Unlike apple, Accede is mainly used as a bloom thinning treatment for peaches and nectarines. It should be applied between bloom and petal fall at 34-69 fl oz/acre rate. However, it was found that two applications (at 10% bloom and full-bloom), each at 34 fl oz/100 gal/acre, can achieve the best thinning results. The product works by causing early senescence to the flowers, thus preventing fertilization and fruit set of the unwanted crop. According to research conducted in MSU in 2021, two applications of Accede, reduced fruit set significantly and cut the time needed for hand-thinning in half, compared to untreated trees.

Source: Dr. Anna Wallis, Apple Production Specialist at MSU

Precautions when using Accede for peaches and nectarines:

This product should not be applied to stressed, unhealthy trees as it may cause over-thinning. If frost occurs during bloom, you should wait until assessing the percentage of frost damage before applying Accede. The product should not be applied if rain is expected within 8h of application. Finally, this product should not be used for peaches and nectarines after petal fall.

Here is a link for the product label for more information about Accede.

https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/AccedeTM_Plant_Growth_Regulator_Label.pdf

MaluSim models for 11 May 2015

Posted on May 11, 2015 by Greg Peck

For both Winchester and Central Virginia, the Malusim model is predicting a mild to no carbohydrate stress over the next week. Although temperatures at the time of application, are less important then the carbohydrate running average (2+4 Running Average), expect chemical thinners applied Sunday (10 May) or Monday (11 May) to cause more thinning than applications made late last week or for the rest of this week. Expect a “typical” response from chemical thinners applied Tuesday (12 May) through the rest of this coming week.

The National Weather Service is predicting sunny weather later this week, as well as daytime temperatures in the 70s. This should result in ideal conditions for plant growth, and thus less carbohydrate stress in the apple trees.

One of the weaknesses of weather-based models, is the need to use forecast data to make decisions about future events. When I ran the MaluSim models for both Winchester and Central Virginia last Thursday, the forecast was for hot, cloudy weather. Although it was in the mid-80s in most of Virginia over the weekend, there was also a lot more sunlight than predicted. Temperatures are generally a lot more reliable than cloud cover predictions, but both seemed to be less severe than originally forecasted.

Cloudy weather predicted for later in the week is causing wild swings in the MaluSim model output. My expectation is that actual carbohydrate levels will be more moderate and that running average values will remain in the 20 to -20 g CHO/day range.

Full model output:

Peck Winchester MaluSim 5_11_15.pptx

Peck Central VA MaluSim 5_11_15.pptx

MaluSim Model Data for 7 May 2015

Posted on May 7, 2015 by Greg Peck

Due to warm days (>80F) and intermittent cloud cover, the MaluSim carbohydrate model is showing a strong carbohydrate deficit for both Winchester and Central Virginia over the next four to five days. Expect an aggressive to very aggressive response to chemical thinners applied today through early next week. Reduce rates, and/or do not include oil or other surfactants if overthinning is a concern. Peck Winchester MaluSim 5_7_15

Pay close attention to the weather forecasts. If actual temperatures are closer to 90F and/or there are prolonged periods of cloud cover, then overthinning will likely occur.

The greatest amount of thinning occurs when fruitlets are on average between 8-12 mm in diameter. Thinning when fruitlets are slightly smaller or larger will result in less thinning, which may be desirable if there is a severe carbohydrate deficit.

Cooler temperatures forecasted for the middle to end of next week should result in less carbohydrate stress and reduced chances of overthinning. However, fruitlets that are greater than 15 mm in diameter are more difficult to thin with NAA or 6-BA.

During these warm days, expect the average fruitlet size to increase by at least 0.5 mm per day.

Full MaluSim model output:

Peck Winchester MaluSim 5_7_15.pptx

Peck Central VA MaluSim 5_7_15.pptx

Central Virginia MaluSim for 4 May 2015

Posted on May 4, 2015 by Greg Peck

Warmer temperatures and cloud cover from some rainstorms later in the week will cause a moderately stronger carbohydrate deficit for Central Virginia.

Thinning applications made Tuesday through Thursday will result in the strongest response this week. Long term weather forecasts predict days in the 80’s and nights in the 60’s for the next 10 days. Carbohydrate levels will likely remain in the 0 to -40 range during that period. To get the strongest response possible, make your applications when average fruit size is 8-12 mm in diameter.

Due to a technical glitch, I was unable to run the MaluSim model for Winchester. I hope to have the problem resolved Tuesday morning. I will post an update for Winchester as soon as possible.

Full MaluSim report:

Peck Central VA MaluSim 5_4_15.pptx

Central Virginia MaluSim for May 1

Posted on May 1, 2015 by Greg Peck

Moderate temperatures and adequate sunlight are resulting in slight carbohydrate deficits according to the MaluSim model.

This means that chemical thinners applied today through the first part of next week should cause an “average” response. Warmer temperatures are forecast for the middle of next week, which should result in greater carbohydrate deficits. I will run another simulation for Central Virginia, as well as the first Winchester run on Monday.

Central Virginia MaluSim for 1 May 2015:

Peck Central VA MaluSim 5_1_15.pptx

MaluSim Model for Central Virginia, 27 April 2015

Posted on April 27, 2015 by Greg Peck

Today, I ran the first Central Virginia MaluSim model for 2015. I will start the Winchester models later this week.

For Central Virginia, I use data from a weather station set up at Silver Creek Orchards and managed by my colleague, Dr. Mizuho Nita. A big thank you to Dr. Nita for allowing me to install the necessary instrumentation and for maintaining the station and associated software.

This year, I will be using forecast data from the National Weather Service. In past years, I used Intellicast.com data because they provided 10-day forecasts with cloud cover predictions. Intellicast no longer provides the cloud cover data in an easy to use format, so I am switching to the National Weather Service’s forecasts. Note that these forecasts only project five days into the future.

We will discuss the details of the model at Tuesday’s meeting at Saunders Brother.

However, this first model run suggests that the relatively cool weather, and mostly sunny weather that has occurred since bud break has resulted in a moderate carbohydrate deficit in apple trees. Growers can expect average results from chemical thinners applied the last couple-few days through to the weekend. In blocks where significant thinning is needed, growers should apply carbaryl at petal fall and then look to the warmer weather that is predicted for the weekend and early next week for their 10 mm application.

Central Virginia weather data, MaluSim data, and an interpretation chart are in the pdf linked to below:

Peck Central VA MaluSim 4_27_15

Impromptu Pruning Discussion, Monday February 23

Posted on February 20, 2015 by Greg Peck

I will be meeting with Bennett Saunders and a few other growers at Saunders Brothers’ Cub Creek Orchard this coming Monday to discuss pruning strategies for tall spindle and other high density orchards.

This will be a fairly informal meeting oriented towards group discussion and demonstrations.

For those who can make it, we will meet at 10AM just inside the gate near the entrance of Cub Creek Orchard located off of Carter Hill Lane, Roseland, VA.

Click here for Google Map directions.

It looks like it’ll be decent weather, but the ground might be a bit wet. Bring your own lunch, loopers, boots, etc.

UPDATE (Sunday Feb. 22): This meeting is still scheduled to proceed as planned. However, only four wheel-drive vehicles will be able to drive further than the orchard entrance. We will coordinate carpools at 10AM.

________________________
Gregory Michael Peck, Ph.D.
Assistant Professor of Horticulture • Virginia Tech
Alson H. Smith, Jr. Agricultural Research and Extension Center
595 Laurel Grove Road • Winchester, VA 22602 • USA
540.869.2560 X19 greg.peck@vt.edu
Tree Fruit Homepage: www.anr.ext.vt.edu/tree-fruit/
Research Homepage: www.arec.vaes.vt.edu/alson-h-smith/treefruit/horticulture/

2015 Winter Fruit Schools

Posted on January 20, 2015 by Greg Peck

The 2015 Winter Fruit School dates, times, and locations have been set. These in-depth meetings focus on commercial tree-fruit production. The schedule will be similar to the 2014 schedule, with the Carroll-Patrick meeting occurring on Tuesday morning and the Central Virginia meeting occurring on Wednesday evening. The full list of locations is below, as well as the local contact for each meeting. NOTE: There is a new location for the Carroll-Patrick Fruit School meeting this year.

Presentations by will include the following topics: brown marmorated stink bug update, tall spindle systems, hard cider resources, neonicotinoid impacts on pollinators, spotted winged drosophila and spotted lanternfly updates, and summer disease management updates with a focus on Glomerella leaf spot. Additional programing is still being developed at each location and more details are forthcoming. Pesticide recertification credits are usually available, check with the local contact for more information.

Date	Location	Registration opens	Local Contact	Contact’s phone number
Tuesday February 10 <Program>	Hungry Farmer Cafe 15297 Fancy Gap Highway (US 52) Cana, VA 24317	9:00AM	Steve Pottorff	276-730-3113
Wednesday February 11 <Program>	Brambleton Center 3738 Brambleton Avenue SW Roanoke, VA 24018	8:15AM	Kate Lawrence	540-473-8260
Wednesday February 11 <Program TBD>	The Nelson Center 8445 Thomas Nelson Highway Lovingston, VA 22949	4:30PM	Michael Lachance	434-263-4035
Thursday February 12 <Program>	Grave’s Mountain Lodge Rte. 670 Syria, VA 22743	8:15AM	Kenner Love	540-675-3619
Friday February 13 <Program & Registration Form>	Best Western- Lee Jackson Banquet Hall 711 Millwood Ave. Winchester, VA 22601	8:00AM	Mark Sutphin & Marsha Wright	540-665-5699

Predicted 2014 Apple Harvest Dates

Posted on July 24, 2014 by Greg Peck

Predicting harvest date depends upon many factors, including full bloom date, accumulated heat units (growing degree days) over the course of the growing season, physiological stressors (e.g., disease and insect damage or drought), day to night temperature differentials as harvest approaches, and the amount of precipitation. However, the number of days between full bloom and harvest has been shown to be the most reliable predictor of harvest date.

Click here to learn more about pre-harvest drop management.

More than two decades ago, researchers in Michigan determined that there there are an average of 143 days between full bloom and the first commercial pick of Red Delicious apples that are to be held in controlled atmosphere storage (i.e., firmness between 17-18 lbs; starch between 2.5-4 on the 8-pt scale Cornell Starch Chart). Additional seasonal adjustments above or below the average number of days until harvest are made based upon the average daily minimum temperatures for the 15 days after full bloom.

For the past several seasons I have tested the Michigan model using fruit from a block of Bisbee Red Delicious on MARK rootstock. Results to date have shown that this model is very good at predicting harvest maturity in Virginia.

Based on the Michigan model, here are the predictions for 2014:

In Winchester, Bisbee Red Delicious full bloom was April 27 and average minimum temperature for the 15 days after full bloom was 0.5°F more than 50°F. Using this data in the Michigan model, harvest is predicted to be 143 days after full bloom. This puts the predicted harvest date for the first CA pick of Red Delicious at September 16.

In Central Virginia (Tyro), full bloom for Red Delicious was estimated to be April 20 and the predicted harvest is September 9.

If you want to compare the model to your own situation, here are the previous years’ predicted harvest dates:

2011 Winchester: September 10
2012 Winchester: August 26
2012 Central VA (Batesville): August 25
2013 Winchester: September 18
2013 Central VA (Piney River): September 15

Since most growers have Red Delicious trees in their orchards, other cultivars (and strains of Red Delicious that ripen earlier than Bisbee) can be estimated based upon experience on their picking date relative to Red Delicious.

Another method for estimating harvest date uses the rule-of-thumb that says, “for each 2-3 days departure for the normal bloom date, there will be a one-day departure from the normal harvest date.” (Blanpied and Silsby, 1992).

You can find more information about harvest maturity indices in this post.

Starting in August, I will start conducting maturity evaluations of fruit from the Winchester AREC and surrounding orchards.

References

Blanpied, G. and K. Silsby. 1992. Predicting Harvest Date Window for Apples. Cornell Information Bulletin 221. <<pdf>>

Beaudry, R., P. Schwallier, and M. Lennington. 1993. Apple Maturity Prediction: An Extension Tool to Aid Fruit Storage Decisions. HortTechnology 3(2): 233-239.