VT Apple IPM – Hang your apple maggot traps any time now

Happy summer:

Apple scab should be pretty much done by now, but be sure to look carefully to ensure that you haven’t had any slip through, as it was certainly windy during a couple of the infection periods this season. If you find no scab in a thorough evaluation of the orchard, that disease is done for this year. Sooty blotch and fly speck (SBFS)would be next on the management agenda, and typically require 270 hours of accumulated wetness starting at 10 days from petal fall. For reference, accumulated wetness in Shoreham (according to NEWA) is about 125, with similar values for other Vermont orchards. Keep an eye on this and apply an appropriate material ahead of any rains as we near the threshold. Honeycrisp growers in particular should also plan on applying a material with efficacy against black rot, which that cultivar is uniquely susceptible to. Common summer fungicides targeted against these diseases include captan in combination with Topsin, a strobilurin (Flint / Sovran), or a DMI (Pristine, Inspire, etc); organic growers may consider Regalia, sulfur, or Serenade, but I am not really sure of theis efficacy. I will say that in 12+ years of managing an organic orchard with a primarily sulfur-based program, I saw almost no SBFS, but plenty of black rot on Honeycrisp especially. Take that as you will.

We’re in a calm spot between insects, but it is time to hang you apple maggot fly (AMF) traps. 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.

Think about including calcium in all of your foliar sprays until harvest, and on Honeycrisp and other large-fruited varieties, you may want to make some specific trips just to get more Ca on.