Author Archives: S. Sherif

About S. Sherif

Dr. Sherif M. Sherif is an Associate Professor of Horticulture at the School of Plant and Environmental Sciences at Virginia Tech, USA. He received both his bachelor's and master's degrees in horticulture from Alexandria University, Egypt, and his doctorate in plant agriculture from the University of Guelph, Canada. Dr. Sherif's broad research experience in molecular biology, plant development, and tree physiology has led him to lead several research projects focusing on the biotic and abiotic factors affecting fruit trees' production, sustainability, and competitiveness. Sherif's current research program at Virginia Tech focuses on frost mitigation strategies, precision crop load management, high-density production systems, molecular regulation of critical horticultural traits, and germplasm development.

Hard Freeze is Expected This Tuesday (March 29)

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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 21oF 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.

Source:New Mexico State University
Source:New Mexico State University

Accede: a new chemical thinning material for apples and peaches

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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

2021 Tree Fruit Extension Survey

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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

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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%). 

Apple Maturity Report-Winchester Sep 22-2021

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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%). 

Apple Maturity Report-Winchester Sep 16-2021

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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

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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 Aug 26, 2021

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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%). 
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

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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%). 
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 13, 2021

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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