Diseases | Credits

SCAFFOLDS Fruit Journal, Geneva, NY                Volume 4
Update on Pest Management and Crop Development    August 28, 1995 


                                                     43F       50F
Current DD accumulations (Geneva 1/1-8/28):         3103      2261
                       (Highland 3/1-8/28):         3225      2365

Coming Events:                              Ranges:
San Jose scale 2nd flight subsides             2494-3191   1662-2302
Apple maggot flight subsides                   2775-3174   1958-2169
Lesser peachtree borer flight subsides         2782-3328   1796-2359
Codling moth 2nd flight subsides               2782-3624   1796-2582
Obliquebanded leafroller 2nd flight subsides   2809-3433   1930-2359
Lesser Appleworm 2nd flight peak               2961-3328   1927-2359
Oriental fruit moth 3rd flight subsides        2987-3522   2018-2377
American plum borer 2nd flight subsides        3005-3587   2154-2497
Redbanded leafroller 3rd flight subsides       3114-3433   2013-2359
STLM 3rd flight subsides                       3235-3471   2228-2472

TRAP CATCHES (Number/trap/day)
                                  8/14   8/16   8/21   8/24   8/28
Redbanded Leafroller               0.3    0.3    0.3    0.3      0
Spotted Tentiform Leafminer        204    550    184    589    185
Oriental Fruit Moth (apple)        7.0   11.3    6.2    7.8    4.8
Lesser Appleworm                   2.1    3.0    1.8    1.8    1.4
Codling Moth                       6.3    2.8    1.1    4.2    2.0
San Jose Scale                     4.6    4.0    3.1      0    0.6
American Plum Borer (cherry)       2.0    1.0    0.5      0    0.4
Lesser Peachtree Borer (peach)     5.0    8.8    2.6    3.3    0.5
Lesser Peachtree Borer (cherry)    2.3    3.8    3.8    0.5    0.5
Peachtree Borer                    1.1    1.0    0.6      0      0
Obliquebanded Leafroller           0.8    0.3    0.7    0.5    0.1
Apple Maggot                       0.6   0.06   0.08      0    0.1

Highland (Dick Straub, Peter Jentsch)
                                  7/31    8/7   8/11   8/21   8/28
Redbanded Leafroller                 0      0    0.2    2.3    3.5
Spotted Tentiform Leafminer       20.3   42.8   33.9   57.8   25.9
Oriental Fruit Moth                1.7    1.6      0    0.1    0.9
Codling Moth                       1.1    0.6    2.4    0.7    0.5
Lesser Appleworm                   1.6    0.7    1.1    0.4    0.2
Sparganothis Fruitworm             0.3    0.2    1.9    1.3    1.8
Tufted Apple Budmoth                 0    0.6    0.3    0.8    0.5
Variegated Leafroller                0    1.1      0    0.4    0.8
Obliquebanded Leafroller           0.3    0.1    0.1    0.3    0.2
Apple Maggot                       0.1    0.3    0.4    0.7      -


By:Dave Rosenberger, Plant Pathology, Highland

Thiabendazole (TBZ) is the only available and effective fungicide for preventing postharvest decays in apples. The most commonly available formulation is Mertect 340-F. Excellent agitation of the drench solution in the holding tanks is essential when Mertect is used. In the past, when Topsin-M and Benlate were used in drench tanks, adequate decay control was achieved even in systems with marginal agitation systems. Topsin-M and Benlate can no longer be used in apple postharvest treatments. As a result, packinghouses now depend on TBZ for decay control in apples. To ensure effectiveness of TBZ, postharvest drenches should be outfitted with an agitation system capable of resuspending any sediment that settles to the bottom of the tank during periods when the system is shut down.

Developing an agitation system: Probably the best and simplest system for agitating drench tanks involves the use of a high-volume pump to recirculate water through "jets" that direct water flow across the bottom of the reservoir tank and create turbulence within the tank. The jets can be made by installing hose connector fittings into a 2-inch PVC line placed in the bottom of the tank. The 2-inch line should have a closed end and be pressurized by a high-volume recirculator pump. It should be possible to use the existing circulator pumps already installed in the tanks if a valve is added so that water can be directed either into the overhead drencher unit or into the agitation system. If the existing pump proves adequate, then the agitation system could be activated for several minutes every hour and for an hour before using the system at the start of each day. An alternative solution would be to use a separate agitation pump that could operate continuously while apples are being treated.

The angle of the hose connector "jets" should be adjusted to direct flow across the bottom of the tanks. Some experimentation will be required to determine the optimum number and angle of jets for each size and shape of tank, but generally jets should be no more than 8-12 inches apart along the 2-inch PVC line. If the system is working properly, turbulence within the tank should be evident at the surface of the filled tank when the system is turned on. The PVC pipe and jets should be plumbed so that the system can be easily removed from the tank when the tank is being cleaned.

Postharvest treatment options: Postharvest treatments for apples are still recommended only when diphenylamine (DPA) is needed to control storage scald. When fruit are treated with DPA, Mertect must be added to the drench solution because the recirculating solutions accumulate spores of Penicillium and Botrytis, which can infect wounds in the fruit. Captan is also registered for postharvest use and can be added to the DPA/Mertect solution, but the benefits of adding captan are debatable. Captan is relatively ineffective when used alone as a fungicide for postharvest decays. However, when used in combination with Mertect, it may help to suppress decays caused by strains of Penicillium and Botrytis that are resistant to the Mertect/DPA combination.

There are four general rules for postharvest treatments on apples:

1. Avoid postharvest treatments when possible: Cultivars like Cortland, Delicious, and Rome are susceptible to scald and should be treated with Mertect/DPA or Mertect/captan/DPA to prevent postharvest disorders if fruit are placed in CA storage. Other cultivars, such as Empire and Golden Delicious, develop little or no scald under New York conditions and can therefore be moved directly from the field into storage. For the past several years, we have suggested that Empire does not need any postharvest treatment. Packinghouse operators are divided in their opinions on this issue. Some operators have found less decay when they stopped treating Empire because fewer of the wounded fruit became infected when the fruit were kept dry after harvest. In other packinghouses, Empire showed an increased incidence of decay when left untreated. Treating Empire with TBZ/DPA may have the added benefit of reducing the incidence of the carbon dioxide injury that has appeared sporadically in untreated fruit over the past several years.

2. Keep drench solutions agitated: With Mertect 340F, inadequate agitation will prove disastrous.

3. 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. Fork-lift operators need to be trained to avoid scooping up soil in the bin runners when they load bins. 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.

4. 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.

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
Dept. of Entomology, NYSAES
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX:315-787-2326

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