The time has come to hang apple maggot fly (AMF) traps in Vermont orchards. Last year, we saw higher populations state-wide, for which I don’t really have a good explanation. These are some of the easiest pests to manage using an IPM strategy, so there’s really no excuse. The idea is to assess the population in the orchard before applying prophylactic sprays. By using red sticky traps, you can time treatments for best effectiveness, and maybe even skip treatments if the populations are low enough. Traps are red plastic balls that you coat with Tanglefoot adhesive. Kits including traps and adhesive are available from Gemplers and Great Lakes IPM.
Traps should be hung at least four per 10-acre block, preferably at the orchard perimeter and especially near sources of the insect, like wild or unmanaged apples. Placement in the tree should be about head-height, and surrounding foliage should be trimmed away- this trap is largely visual, and you should be able to see it from 10-20 yards away. The traps may be baited with an apple essence lure that improves their attractiveness dramatically. For monitoring to time sprays, unbaited traps that catch one fly per block (as an average of all the traps in the block) would warrant treatment; the lure makes them much more attractive such that you can wait until an average of five flies per trap are caught before treating. For most growers, the main insecticide used against AMF is Assail, Imidan also works but it has a long reentry interval and tends to leave visible residue on fruit. For organic growers, Surround works well, but its use in midsummer may increase European red mites, and it can be hard to remove at harvest; spinosad (Entrust) works pretty well too. First AMF treatment is still a few weeks off, most likely
It is summer lepidoptera season, and treatment should be on everyone’s minds, especially for codling moth (CM) and obliquebanded leafroller (OBLR). CM are active and eggs hatching or soon to hatch across the state, so growers who have caught CM in their traps or who often have issues with this pest (that’s most everyone) should apply something effective against them soon. Very specific materials like insect growth regulators (Intrepid, Rimon) or granulosis virus (Madex, Cyd-X) can be used that are very safe to non-target insects. One or two applications of a material should suffice for first generation. OBLR are just showing up in traps, and treatment should be timed at 360 degree days (base 43°F) after first catch. There is a NEWA model for this pest, and a material like Bt (Dipel, etc.) is effective (but not against CM).
Mites are a no-show statewide. Keep scouting leaves, as their populations can grow very quickly, especially as the weather heats up.
Diseases: keep checking on your scab, if you have none (I mean none), then it’s okay to relax. The summer diseases sooty blotch and flyspeck are of concern now, but they require 270 hours of leaf wetness for lesions to form, so fungicide coverage between that period should be maintained. Keep in mind that one inch of rain washes off half of your coverage, after two inches, it’s gone.
Enjoy the holiday this week and remember that trees shouldn’t be sprayed when it’s over 80-85, and application of sulfur, captan, and other potentially phytotoxic materials should be avoided when hot weather is in the forecast for the next couple of days.
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