Diseases | Credits

SCAFFOLDS Fruit Journal, Geneva, NY             Volume 5 
Update on Pest Management and Crop Development August 26,1996

Coming Events

                                                     43F       50F
Current DD accumulations (Geneva 1/1-8/26):         2764      1904
                       (Highland 1/1-8/26):         3250      2265

Coming Events:                             Ranges:
Apple maggot peak flight                        2033-2688  1387-1778
STLM 3rd flight peaks                           2033-2688  1387-1778
Peachtree borer flight subsides                 2230-3255  1497-2309
Redbanded leafroller 3rd flight starts          2389-3113  1722-2209
Oriental fruit moth 3rd flight peaks            2389-3267  1712-2326
San Jose scale 2nd flight subsides              2494-3191  1662-2302
Obliquebanded leafroller 2nd flight peaks       2634-3267  1789-2231

TRAP CATCHES (Number/trap/day)
                                   8/5   8/8  8/12  8/19  8/22  8/26
Redbanded Leafroller                 0     0     0     0     0     0
Spotted Tentiform Leafminer         66   163    96   465   372   318   
Oriental Fruit Moth                3.9   4.2   5.6   5.2   4.5   8.8
Lesser Appleworm                   0.8   1.0   2.5   1.2   1.0   4.0
Codling Moth                      13.9  17.7   8.5  11.0  21.0   5.0
San Jose Scale                     6.3   7.0   1.4   3.3   1.7   3.3
American Plum Borer                3.9   3.7   1.6   4.4   4.3   2.8
Lesser Peachtree Borer (peach)     0.4   0.3   0.8   1.5   0.3   1.6
Peachtree Borer                    4.8   2.7   3.0   3.8   1.2   0.1
Obliquebanded Leafroller             0     0     0     0   0.2   0.1
Apple Maggot                       0.3   0.4   0.1   0.1   0.1     0

Highland (Dick Straub, Peter Jentsch)
                                  7/22  7/29   8/5  8/12  8/19  8/26
Redbanded Leafroller               0.1   0.3   0.2   0.3   1.0   0.9
Spotted Tentiform Leafminer       27.9  19.1   109   152   153   102
Oriental Fruit Moth                0.9   0.2   0.1   0.5   0.2   0.1
Lesser Appleworm                   0.4   1.9   2.5   3.5   5.4   5.4
Codling Moth                       1.4   6.2   8.9   4.9   3.9   0.9
Fruittree Leafroller                 0     0     0     0     0     0
Tufted Apple Budmoth               0.4     0   0.1   0.2   0.4   0.6
Obliquebanded Leafroller           0.2     0   0.3   0.7   0.4  <0.1
Sparganothis Fruitworm               0     0     0   0.1   0.2   0.7
Variegated Leafroller              0.1   0.2     0   0.6   0.5   0.4
Apple Maggot                       0.8   0.9   3.4   2.1   1.0   0.6
                                                       * = 1st catch
                                                     43F       50F



By: Dave Rosenberger, Plant Pathology, Highland

Postharvest fungicide treatments for apples are essential whenever diphenylamine (DPA) is used to control storage scald. When fruits are treated with DPA, the recirculating drench solutions accumulate spores of Penicillium and Botrytis. These fungal pathogens infect wounds (stem punctures, injuries caused by pickers, etc.) and cause decay of the fruit during storage. Thiabendazole (TBZ) must mixed with the DPA drench solution to control postharvest decays. Mertect 340F is the most commonly available formulation of TBZ.

Empire apples rarely develop scald when grown under NY conditions and therefore do not require DPA treatment. Many packinghouse operators have been moving Empire fruit directly into CA storage without any postharvest treatment, and some of them have been very satisfied with the low incidence of postharvest decays. Other packinghouse operators have reverted to treating Empire fruit with the DPA/TBZ mix because they have encountered intolerable levels of decay in CA Empire fruit that had not been treated. Although there are some exceptions, the current trend is that Hudson Valley growers have not experienced significant decay problems with untreated Empire, whereas storage operators in western and central New York are reverting to using a postharvest treatment for CA Empires. Reasons for these differences have not been determined.

Recent work by Dr. Chris Watkins at Cornell and Ken Silsby in western NY have shown that there may be indirect benefits from giving Empire fruit a postharvest DPA/fungicide treatment. DPA apparently eliminates the carbon dioxide/chilling injury that has appeared sporadically on some lots of Empire fruit. In some years, DPA treatment has also resulted in slightly improved fruit firmness when apples were removed from long-term CA storage. However, these indirect benefits of DPA treatment probably do not justify applying postharvest treatments unless there is also a concern about controlling decays.

If Empire fruit will NOT be given postharvest treatments, storage operators may wish to employ some of the following precautions to limit the potential for postharvest decay problems:

1. One or two applications of Benlate-Captan or Benlate-Ziram should be applied to Empire blocks in late summer, with the last application sometime between 10 and 30 August. Benlate will provide better residual activity than Topsin M.

2. Inoculum levels are likely to be higher on fruit that are hanging less than 18 inches from the ground at harvest. Postharvest pathogens survive in soil beneath trees and are likely to be rain-splashed onto low-hanging fruit. Fruit from orchards with a lot of low-hanging fruit are at greater risk for postharvest decays and may benefit from a postharvest treatment.

3. Inoculum for postharvest decays can accumulate and survive on wooden apple bins. Given the option, use newer bins or plastic bins for Empire fruit that will not be drenched.

The following guidelines should be followed whenever postharvest treatments are applied to apples of any variety:

1. Always apply DPA and TBZ together. Neither product should be applied alone in a postharvest drench. Some of the postharvest pathogens are resistant to TBZ, but the TBZ-resistant isolates are usually controlled by DPA. Thus, both products are required to control the full spectrum of pathogens. As noted earlier, DPA should not be applied alone because the DPA drench will collect spores and will increase the incidence of decay in fruit if a fungicide is not included in the drench.

2. Never mix any chlorine products with DPA/fungicide treatments. Chlorine disinfectants may react with DPA and Mertect.

3. Cool treat fruit as rapidly as possible after treatment. The activity of DPA against TBZ-resistant pathogens is very limited at temperatures above 40F. If apples are cooled slowly, TBZ-resistant Penicillium can initiate decays before the antifungal activity of DPA "kicks in".

4. Keep drench solutions agitated. With Mertect 340F, inadequate agitation in the drench tank will prove disastrous because all of the active ingredient will settle to the bottom of the tank. The best system for agitating drench tanks involves the use of a high-volume pump to recirculate water through PVC "jets" that direct water flow across the bottom of the reservoir tank and create turbulence within the tank. An agitation system should be considered inadequate if it is not capable of resuspending virtually all of the sediment from the bottom of the tank when the system is activated after an overnight shut-down.

5. Keep drench solutions clean: Soil introduced into the postharvest treatment tanks carries decay inoculum and makes it more difficult to keep postharvest chemicals in suspension. A pre-wash with a high-volume stream of non-recycling water may be needed to remove soil from bins or equipment before they enter the postharvest drencher. Empty and clean tanks at least as frequently as is required on the DPA labels.

6. Keep drench solutions properly recharged: The drench solutions should be regularly recharged according to instructions included on the postharvest labels of the products being used.

A new biological postharvest fungicide, Aspire, will be available from Decco this year in some states. However, the capabilities of this product have not yet been adequately researched and the status of the label for New York State is unclear. Captan is also registered for postharvest use and can be added to the DPA/Mertect solution. However, Captan has shown only marginal activity against postharvest decays in our tests and is not recommended.

Scaffolds is published weekly from March to September by Cornell University -- NYS Agricultural Experiment Station (Geneva), and Ithaca-- with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:

Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Department of Entomology, NYSAES
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX:315-787-2326

Back to the Scaffolds 1996 Directory
Scaffolds 1995 Directory