Maine had two bouts of fire blight weather during bloom, one at very beginning and second at very end. I suspect that the rapid shift to hot days just before and leading into bloom (after slow cool period from bud break to pink) may have shocked the trees and resulted in more straggled bloom than usual.
While we have not had an epic fire blight year comparable to what other states have experienced in other recent years, there seems to be a transition this year. Originally fire blight was not a disease that required attention in Maine. That era ended about 15 years ago. Then, fire blight used to be something that showed up in a few orchards in some years, usually but not always relatively minor extent. This year, it seems that most orchards have a little bit of fire blight. No devastating epidemics this year, but a lot more than growers want to see. Following is off the cuff reply to apple grower dealing with fire blight strikes that keep showing up in Paula Reds. He was wondering if he can ever dig his way back out of recurring fire blight infections. The fire blight has been in the block at low level for past 3-4 years and despite repeated, (though not always immediate) sanitation removal, it is back again this year. Still not at catastrophic level but it does seem to be increasing year to year. Rough guess is that this year 20-30% of Paula Red trees in the block are affected. Most with only one or two strikes, but a few with considerably more. Unfortunately I think the trees are on M26. Across Maine. there seems to be much more fire blight on Paula Red than other cultivars this year. Honeycrisp and Cortland in this same block hardly affected. I'm looking for comments. Did I miss any key points? Anything erroneous? I'm aware of kasugamycin and other alternative materials, but this wasn't the place for getting into that kind of detail. I don't think we have strep resistant E.a., should get some more samples tested though. Is two early season copper applications likely to be any more helpful than one? Post harvest copper make any sense? Thanks for your help, Glen ************************************** Grower message: "Fire blight looks like heck in the Paula Red’s! We are just cutting what we can and summer pruning. Is there no hope?" Reply: " It should slow down with trees ceasing terminal growth. I'm sure you have other things you'd rather be doing, but getting rid of the fire blight now will at least cut down work load later, and might be the thing that prevents further spread that gets to the point where you are looking at replacing trees. Copper every spring. Strep on hand so you can react quickly to blossom blight infection period forecast that you need to check daily because they can change so fast. Factor fire blight into cultivar and rootstock selection. Blossom removal on first year trees. Fertility management to prevent overly lush growth. Consider Apogee where appropriate to reduce shoot growth and thus shoot blight spread. Daily monitoring and removal of fire blight strikes starting a petal fall until end of August. Strep on hand in case hail or strong wind storm creates risk of fire blight spread (up until strep PHI gets in the way). Be careful that you don't mix summer pruning and fire blight removal. They should be handled as two separate jobs. I suspect it would be best to complete fire blight removal first. Summer pruning before fire blight removal will create open wound surfaces. Going in after to handle fire blight material could mobilize bacteria which can infect those wounds. Thus, better to remove fire blight before creating summer pruning wounds. Same thing applies to sucker removal. Thoroughly sterilize tools after using them for fire blight removal before using for anything else. Ugly stub pruning to allow winter removal of cankers created by sanitation cuts. Don't leave fire bight cuttings in the orchard as fire blight bacterial can remain active in dried ooze for 2 years. Burn, bury, or compost the fire blight cuttings. It is possible to work your way out of a moderate fire blight outbreak. But it can take an extended period of sanitation vigilance. There are no silver bullets." ************************************** -- Glen Koehler University of Maine Cooperative Extension Pest Management Office Voice: Office 207-581-3882, Cell 207-485-0918 491 College Avenue, Orono, ME 04473
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