June 25, 2020
Hopefully everyone had some fungicide coverage on for that last rain we got yesterday. It’s hard to tell without doing proper spore counts, but I feel pretty confident saying that primary scab season is done for this year. Scout your orchards for lesions and protect from secondary infections if you find any. But really, this has been a pretty easy scab season.
Keep looking for fire blight and remove as soon as you see it. If you have any big outbreaks, let me know. My Cornell colleagues Dr. Kerik Cox and Anna Wallis are collecting samples of fire blight-infected tissue to test for antibiotic resistance in the pathogen. If you can participate, I’ll be happy to help with collection and shipping if I can do it in a timely manner.
If codling moth is a serious pest in your orchard, you may be due for a second treatment with an effective material. Otherwise, you’re likely in between insect concerns until apple maggot and/or obliquebanded leafroller come around. Now is the time to get apple maggot fly (AMF) traps up. 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.