Early summer orchard considerations

By Terence Bradshaw

I’m not sure if everyone reads all the way to the bottom of my postings, or if things are going fine in Vermont orchards. If you recall, I was away working with apple growers and aspiring cider makers in Lebanon May 26-June 10, and was mostly unreachable. That I heard very little from growers suggests that either things are pretty quiet or I’m not needed. I’ll assume the former. I’ll also plan on presenting a trip report at the winter VT Tree Fruit Growers Association meeting, There are quite a few lessons we can learn from where the Lebanese apple industry id now, compared to our own situation now and especially over the past several decades. Stay tuned.

This week I’ve been getting caught up at the farm, in class, and with some upcoming research reports. Orchards are generally looking good. Primary apple scab is done, and if you missed infection periods, you’ll see lesions now. If you have scab in the orchard, keep covered with captan (sulfur if organic) and watch for lesions to burn out during hot/dry periods. It’s been dry and looks to stay that way (mostly) outside of rain expected on Monday. The next diseases to think about, assuming you have scab under control, are the summer tots and sooty blotch/flyspeck. Those all need substantially more moisture than we have had or are expecting, so sit tight. You can hold off on the fungicides for a while.

Monday I saw one single fire blight strike. That is important for two reasons. First, it confirms the predictions in Maryblyt that infections from the infection periods that may have occurred around May 25. Second, this strike was found in a Crimson Gold tree in our organic block. We do not use antibiotics in that block, and have suffered from substantial infections in most years. That we found one strike, and none on our most sensitive cultivar, tells me that that infection period was indeed relatively weak. Keep an eye out for strikes in your orchards and prune out when you see them, but I’d say we’re generally done worrying about fire blight for 2018.

Insects are another matter of course. Plum curculio (PC) are largely done in most orchards except inland/upland cooler sites- keep an eye on developing fruitlets for fresh damage and treat if needed. Perimeter sprays should be sufficient there. Codling moths (CM) are active and the eggs from the first flights are hatching. If you have had issues with this pest in your orchard, we’re in a good window to manage them. A broad-spectrum material could manage both CM and PC, but if you’re only concerned about the former, consider using one of the softer, lepidopteran specific materials like granulosis virus (e.g., Cyd-X) or an insect growth regulator (e.g., Rimon, Esteem, Intrepid) which are much safer on beneficial insects. Esteem is also effective against San Jose scale which are susceptible now if you’ve had a problem with those insects recently.

Obliquebanded leafrollers are just starting to fly now, there are a couple of weeks before we need to worry about them. As the weather turns hot and dry (trust me, it’s coming), keep an eye out for mites. Ideally, newer ‘soft’ IPM programs will help to maintain mite predator populations such that pest mites don’t require treatment beyond spring oil application.

Horticulturally, think about getting on any last nitrogen fertilizers before it gets too late and risks reducing cold hardiness. Where needed, magnesium and potassium may be ground-applied. Make sure to keep training new trees. As for thinning, the window to chemically thin has mostly closed. That said, if you still have too many fruit set, rescue thinning with Ethephon is an option that may be used cautiously.

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