Author Archives: S. Sherif

DA readings refer to the level of chlorophyll (green color) in the fruit’s mesocarp, just below the skin. As the fruit ripens, chlorophyll levels decline, and so do DA readings. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the level of fruit maturity and 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%). 

Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035, Email: ssherif@vt.edu

Apple Fruit Maturity Report-Winchester-Sep 16, 2020

DA readings refer to the level of chlorophyll (green color) in the fruit’s mesocarp, just below the skin. As the fruit ripens, chlorophyll levels decline, and so do DA readings. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the level of fruit maturity and 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%). 

Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035, Email: ssherif@vt.edu

Apple Fruit Maturity Report-Sep 9, 2020

DA readings refer to the level of chlorophyll (green color) in the fruit’s mesocarp, just below the skin. As the fruit ripens, chlorophyll levels decline, and so do DA readings. Starch index, fruit firmness, and, to some degree, Brix values are commonly used to determine the level of fruit maturity and 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%). 
Fruits collected from 19 apple varieties grown in the AHS Jr. AREC, Winchester, VA, on Sep 9, 2020 to assess fruit maturity indices.

Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035, Email: ssherif@vt.eduFacebookTwitterEmailShare

Apple Fruit Maturity Report-Sep 2, 2020

The DA reading indicates the level of chlorophyll (green color) in the mesocarp of 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. Generally speaking, fruits for CA should be harvested at starch index (3-5), firmness (> 16 lb), and DA reading (0.60). For fresh consumption, fruits at starch index (5.5-7), firmness (13-16 lb), DA reading (0.35) and Brix (12-14%) would be ready for harvest.
Starch iodine test was conducted on Sep 1, 2020, for 19 apple cultivars grown at the AHS Jr. AREC, Winchester, VA. Starch values were estimated according to the Cornell starch index (1-8). The recipe for the starch iodine test was described in a previous post ((https://blogs.ext.vt.edu/tree-fruit-horticulture/2012/08/23/harvest-maturity-resources/)

Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035, Email: ssherif@vt.edu

Apple Fruit Maturity Report-Aug 21-2020

The assessments of fruit maturity parameters were conducted at the AHS Jr. AREC, Winchester, VA.  
Fruits for CA storage should be harvested at starch index (3 – 5), firmness (> 16 lb), and DA reading (0.60). Fruits intended for fresh consumption should be picked at starch index (5.5 – 7), firmness (13 – 16 lb), DA reading (0.35) and Brix (12-14%).
Starch iodine tests for 19 apple cultivars grown at the AHS Jr. AREC, Winchester, VA. Starch values were estimated according to the Cornell starch index (1-8). The recipe for the starch iodine test was described in a previous post ((https://blogs.ext.vt.edu/tree-fruit-horticulture/2012/08/23/harvest-maturity-resources/)

Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035, Email: ssherif@vt.edu

Apple Maturity Report-Winchester-Aug 19, 2020

Greetings,

Below is the apple maturity report for the Winchester/Fredrick county area. We measured fruit firmness (lb), fruit color, total soluble solids (Brix), and starch conversion rate (1-8 index) for 11 apple cultivars grown in the AHS Jr. AREC’s and we will keep sending similar reports throughout the harvest season to help you decide the optimal harvest date for your cultivated blocks. More varieties will be added to or dropped from 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 assess fruit coloration. The DA device measures the chlorophyll content in the mesocarp of 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 atmospheres (CA) storage or fresh consumption. If you don’t see your variety in the list, you can generally pick your fruits 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 the starch index (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.

The values represent the average of 5 fruit/each variety.
The starch-iodine test for Gala and Honeycrisp apples- Aug 18, 2020
This table was adapted from the Michigan State University website

Sherif M. Sherif, Assistant Professor of Horticulture at Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035, Email: ssherif@vt.edu

Apple carbohydrate thinning model this week (May 23) for Winchester

Greetings,
The weather network predicts a sunny and warm weather this week, and you might feel it’s the time to give thinning your best shot. So, let me remind you that thinning treatments take at least 7 days to show an effect if the weather was warm; and almost two weeks (if not more) if the weather was cold. With all the cold weather we had in the past two weeks, if you applied a thinning treatment two weeks ago, you should start seeing an effect on the tree now. However, if your last thinning treatment was a week ago, you should give it 4 more days (from today) to check your trees and see if more thinning is required.

If you will apply any thinning treatment tomorrow or Monday (May 24, 25), the carbohydrate model suggests increasing the rate of thinning materials by 30%. I, however, would recommend applying the standard rate. Temperatures are expected to be above 85 OF for several days by the end of this week, which may put the trees under stress, turning them oversensitive to thinning materials. This year, it’s normal to see on the same tree fruit that are 18-22 mm in diameter and others that range between 11-14 mm. Thinning treatments by 6-BA and NAA will only be effective on fruit that are less than 18 mm in diameter.

The carbohydrate thinning model for Gala apples in Winchester, VA. Green tip date= 3/16; Bloom date=4/20; Percent flowering spurs (51-75%).


Sherif M. Sherif, PhD
Assistant Professor
Virginia Tech, School of Plant and Environmental Sciences,
AHS Jr. Agricultural Research and Extension Center
595 Laurel Grove Road, Winchester, VA 22602
Tel. 540-232-6035  Email. ssherif@vt.edu

Apple Carbohydrate Thinning Model-Winchester-May 20, 2020

If you plan to put any thinning treatments tomorrow or Friday, the model suggests increasing the chemical thinning rate by 30%. I would recommend postponing thinning treatments until Saturday or any day next week for three reasons: a) 6-BA and NAA treatments will be more effective as average daily temps. are predicted to be above 70 oF. b) only apple clusters from late bloom will be responsive to your thinning treatments whereas those resulted from early bloom and that represents the primary crop would be less affected by thinning next week; and c) Fruits affected by past frost events would be more likely fallen by that time, allowing you to make a better assessment of your crop load and the need for any further thinning.

Sherif M. Sherif, Assistant Professor of Horticulture, Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center, 595 Laurel Grove Road, Winchester, VA 22602 Tel. 540-232-6035 , Email: ssherif@vt.edu