May 14, 2017
Orchards in the Champlain and Connecticut valleys are in full bloom now, and it looks like a good one. After my worrying comments last week about poor weather for bee flight, one grower last Monday told me, “You’re worrying too much. It’ll happen.” And it looks like Thursday and Friday the bees were flying. Although I am not trapping for native pollinators this year, I did notice some small native bees in trees in Putney Thursday afternoon. I wasn’t at the UVM orchard Friday, but my technician told me the bees were moving well. Orchards in cooler upland and inland spots will likely be flowering later this week, which also looks like a period of decent (>60° and sunny)bee weather.
Since we are talking bees, we need to continue to keep them in mind as we begin to think about petal fall and insect pest management. We have found extremely low levels of the usual pink/petal fall insects, tarnished plant bug (TPB) and European apple sawfly (EAS), in orchards all across the state. Some growers predicted and I confirmed a suspicion of a protracted bloom and therefore applied prophylactic insecticides at pink. In terms of bee protection, that is a valid response as long as those who applied a broad-spectrum, non-neonicotinoid material at pink use that extra protection they applied to give a little more time for all petals to drop and to clear out other attractive blooms by mowing before applying the next insecticide. This is our most dangerous timing for potentially damaging bees, because we need to get in to protect the developing crop, but there is still potential for a lot of pollinator activity in the orchard. Remember, pollinators aren’t just the honeybees you bring in to the orchard, and as we have been developing softer, more pest-specific spray programs in recent years, we are encouraging pollinator conservation in the orchards (good), which increases the number of pollinators that could be impacted when we apply that important post-bloom insecticide (not good).
I have been advising growers who are either still at pink or approaching petal fall who have below-threshold populations of TPB and EAS but who have concerns about lepidopteran pests now to consider using only a Bt spray like DiPel. Green fruitworms and obliquebanded leafroller are active now and may be monitored by inspecting 100 blossom/fruitlet clusters and terminal tips in multiple sections of the block and looking for larvae (small green caterpillars). Bt is very effective against moth larvae but has no known effect against most other insect orders, including bees.
Speaking of moths, if you have not already done so, now is the time to hang codling moth (CM) traps in the orchard. These traps are baited with either a pheromone (most common) or fruit volatile (used where CM mating disruption is used) lure and is used primarily to set the biofix date for use in the CM development model in NEWA, so daily or at least 2-4 times per week inspection is needed until the first moths are caught. Trap counts may be collected for the rest of the season to gauge population size and flight patterns. I mentioned CM mating disruption. We have been using this tactic since 2011 after suffering 65-75% damage in our organic orchards at the UVM Hort Farm. This year we have started using a Trece product, Cidetrack CMDA Meso, which reduces the needed number of applicators per acre from up to 200 to 36. This greatly affect the ability of larger-acreage orchards to hang the dispensers. Eric at CPS can provide details on availability and pricing, but growers who wish to try them must be prepared to treat the whole orchard, and should get them up as soon as possible before CM start flying and mating. A good background on using mating disruption in orchards can be found here. It’s a little bit old so the products listed may not be available or registered for use in Vermont.
Fire blight continues to be a non-issue for now, but increasing temperatures forecast for next weekend may trigger an infection, I’ll keep you posted as things develop. Keep in mind that bacteria need open blossoms to cause blossom blight, so as your petals fall, so does your risk. Scab- it’s still active, and I assume everyone is protected for today’s rain. As we get into the late bloom/petal fall window, addition of a material to the usual protectant (mancozeb/captan/sulfur if organic) schedule may be prudent. Consider a strobilurin (IRAC class 11), SDHI (7), or, if the bees are all gone, DMI (3) fungicide in your next spray or two.
Thinning is going to be interesting this year. Every orchard I have seen will need thinning, and I am going to work up some thoughts on recommendations later this week.
Finally, I have been asked to pass on to the orchard community that Dave Boyer, from Boyer’s Orchard in Monkton passed away last week. His obituary can be found here.
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