Cooling off orchard activities

By Terence Bradshaw

Now that we have a respite from the heat wave, I imagine growers are thinking about what needs to be managed in Vermont orchards. As a rule, there aren’t any across-the-state IPM issues that I expect every grower will be facing. In warmer areas, it’s still a decent time to apply a second codling moth spray if your trap capture were high, say consistent 7-10 or more per trap during the peaks, In cooler regions, this is a good time to cover for emerging larvae, again, if your trap catches were high. It’s early to treat for obliquebanded leafroller, and apple maggot traps were just barely deployed last week on most farms. That said, I’ve seen at least one orchard with very high trap catches, and remember that an average over five flies per baited red sphere (or one per unbaited trap) indicates a need to cover. Most growers are using Assail against apple maggot, and it is also effective against codling moth and several other secondary pests.

Mites are likely to be an increasing problem with the heat we experienced, especially where pyrethroids or organophosphates have been used. Use this chart to guide mite scouting. The threshold in July is five European red or two-spotted spider mites per leaf. There is a number of materials available for use against mites, see the New England Tree Fruit Management Guide for details. If mites are a problem, consider a thorough oil application next spring and moving away from broad-spectrum insecticides. You may need to reintroduce predators from an orchard with a good population of them, but it can be well-worth it.

Diseases are pretty quiet. For the few that have scab, keep maintaining some captan coverage, between that and the heat (more is on the way for Monday), it should burn out. I’ve heard few reports of fire blight, but if you have it, keep cutting it as you see it. Sooty blotch and flyspeck are still awaiting another 100+ hours of wetting. Powdery mildew should have been shut down by the heat wave, but if you have it on susceptible cultivars (e.g. Cortland, Honeycrisp), sulfur, a strobilurin, or a DMI fungicide should take care of it. I’d aim for the first, given its low cost and lack or issues with resistance, and save the others for late-0season rots or summer diseases if it ever gets wet enough.

Speaking of wet, I don’t need to tell anyone that it’s dry out there. Water if you can, and remember that consistent moisture is better for trees than infrequent flooding. Also remember that inadequate soil moisture is linked to poor calcium (and other nutrient) uptake in trees and can exacerbate bitter pit, so every spray should include calcium and you may consider going out just top put that nutrient on to susceptible cultivars (again, Cortland, Honeycrisp).

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