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

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

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

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 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.

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

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.

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

Subfreezing temperatures as low as 30 oF is expected midnight tonight (Friday) to 10:00 am Saturday for northwest and western Virginia. Our cherries, peaches, and most, if not all, apple varieties are at the post-bloom stage now. The critical temperatures that can cause 10% and 90% of damage at this stage are 28 oF and 25 oF, respectively. At this stage of apple crop development, frost can cause damage to the fruits and seeds. Fruits with damaged and aborted seeds stop growing and eventually drop off. Therefore, it’s important to assess your crop first for any frost injury before starting thinning applications this coming week. You can do so by picking a few fruitless from different locations in the orchard and cut them in half by a pocket knife and observe the flesh and seed color. Damaged fruitlets will show brownish flesh and seed color. In most cases, the damage can also be observed on the fruit surface as a frost ring (See images below). 

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

The average fruit size for our Gala, Pink Lady, Red Delicious, Fuji, and Honeycrisp in the Winchester area is 6.00, 6.11, 6.04, 5.72, and 6.37 mm, respectively. So, you may be wondering whether you should put any thinning application this week and if yes, when to spray and at what rate?!

The short answer is yes. You may consider applying chemical thinners, e.g. 6-BA or NAA, for your apple trees this week, preferably tomorrow, May 2nd, and Sunday (if it’s not raining). Based on the 10-d weather forecast for Winchester, it will be only Saturday and Sunday this week with temp. above 70 oF. Both 6-BA and NAA work better when the temp is greater than 65 oF. As for the rate, the carbohydrate model recommends increasing chemical thinning rate by 30%. Two things to consider here: a) Apple cultivars respond differently to thining materials. Golden Delicious, Fuji, and Cameo are usually hard-to-thin, whereas Pink Lady, Gala, Honeycrisp and Granny Smith are easier to thin. For the rates and materials recommended for Gala, Fuji, Honeycrisp, Red Delicious, Pink Lady, and Golden Delicious, use this link (https://blogs.ext.vt.edu/tree-fruit-horticulture/2020/04/02/fruit-thinning-scenarios-2020/). b) The rates mentioned on 6-BA and NAA product labels are for dilute applications (100 gal/acre). To convert from dilute to concentrate, please refer to my other post at (https://blogs.ext.vt.edu/tree-fruit-horticulture/2020/04/02/how-to-calculate-the-tree-raw-volume-trv-and-chemical-rates-for-concentrate-spraying/). 

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