Codling moth and other pest management in apples

By Terence Bradshaw

Codling moth (CM) management is just around the corner in many Vermont orchards. This is an increasing pest in the state- many orchards never had a problem until recently, and some still don’t. Adults begin flying around bloom, and our monitoring program is designed to catch the first flight to tie later management applications. Mated females lay eggs in the tree canopy and hatched larvae burrow into fruit causing significant damage in some orchards. It is the larvae that are generally targeted for control. Materials effective against larvae include many broad spectrum pesticides that may also have substantial non-target impacts on beneficial insects. If you need a late petal fall cover effective against plum curculio (PC) or European apple sawfly (EAS), then a broad-spectrum material may be needed. However, if targeting CM specifically, then a more specific material may be called for. As I mentioned last week, there are a number of materials that have high efficacy against CM and low non-target impacts, including granulosis virus, insect growth regulators like Intrepid and Rimon, and some more lep-specific materials like Delegate and Altacor. Applications should be made about 250 degree days (base 50°F) from first trap capture. In South Burlington, current DD since the first capture is 193 as of today, with 250 predicted by Sunday. So the next spray application should include a CM-specific material if they have been a problem in your orchard and you are located in a warmer area like the Champlain or Connecticut Valleys.

San Jose scale is another insect which is increasing in Vermont orchards. Crawlers emerge about 500 DD base 50 from March 1; that should occur mid-late next week in the warmer sites and a bit later in the cooler ones. Some scale-specific materials include Esteem, Movento, and some of the neonicotinoids like Assail and Admire Pro, which may have activity against other pests, especially Assail which is fairly effective against CM, PC, EAS, and a number of other insect pests.

Disease: I recommend one more fungicide cover until we can get a handle on what the scab situation is next week. Captan (sulfur if organic) is fine, adding a DMI, stroby, or SDHI will cover for rusts and/or powdery mildew.

Fertilizers: I haven’t discussed them much this season. Nitrogen applications should be wrapping up by the middle of the month. Calcium applications, both ground (gypsum or calcium nitrate in that last N application) and foliar, should start now. If needed, magnesium and potassium applications can also begin any time now. Consult your leaf analysis for determining these.

Thinning: most orchards should know the fruit set, thinning, and general crop load status by now. If you need additional thinning, the window will start to close after this weekend. Maxcel and other 6-BA thinners will finally start to work given the upcoming heat. Also, remember that the leaves are soft and trees will thin easily, so don’t overdo it.

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