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According to captures of plum curculio on traps designed to intercept PCs moving from overwintering sites into orchard blocks, PC immigration remained low over the weekend, suggesting that we are likely seeing the tail end of PC invasion into orchards. However, the question remains as to how big the tail end is, and how long it will last. To put things in perspective, weekly captures across all interception traps (112 traps in all) are as follow:
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Week Ending |
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May 10 |
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May 17 |
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May 24 |
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May 31 (through May 30) |
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Given these data, commercial orchards have already faced the majority of immigrating PCs, and it appears that control of the first, dominant wave of immigrants in early May was excellent.
We have yet to see buildup of evidence of substantial PC egglaying or feeding in any monitored sites—most sampled commercial orchards (those covered by private consultants and our own sampling) remain entirely free of PC damage. Even in unmanaged trees sampled in conjunction with commercial sites, damage remains very low, with no sites exceeding 10% cumulative PC injury. However, PC egglaying is largely temperature-driven, and those adults present even in unsprayed trees simply have not had weather conducive to concerted activity.
With the lull in PC immigration after the first week of May, coupled with near total lack of weather inspiring egglaying activity, most commercial orchards should enjoy relatively straightforward, effective PC control. As immigration remains at a consistent trickle, border-row treatments should suffice—providing acceptable control of sluggish PC as their invasion tails off. Although combined data suggest that there are relatively few PCs still moving into orchards, growers should bear in mind the likelihood of drawn-out activity of the stragglers, and the potential for accumulation of substantial damage from spikes in late activity. Even with the low levels of PC damage thus far, growers are advised to continue monitoring perennial hotspots for flushes of injury.
It may seem contradictory that we believe most PC have already entered orchards and have been controlled, but recommend continuing border-row coverage for control of late immigration. In our judgment, border-row sprays against light, lingering invasion offer the best tactic for alleviating the risk of damage from late PC activity—managing late immigrants without the investment of whole-orchard treatment.
All of this ties in to the annual question of determining the end of the PC threat. Along with regular sampling of traditionally PC-heavy areas, a degree-day model was developed in New York to assist growers in determining when PC season is nearing its end. According to this model, the last treatment against PC should be applied such that the residual effectiveness of the material (10-14 days, depending on material, formulation, and weather) will protect the orchard through the accumulation of 340 degree days (DD) after petal fall. To calculate DD, take the average of the day’s low and high temperatures (in oF), then subtract 50 to determine the day’s DD total.
Remarkably, data from our monitored sites yield accumulation of 40-80 DD in the weeks since petal fall (compared to 120-170 DD at this time last year), indicating that the PC season still has a long way to go and is passing very slowly. All told, it is best to err on the side of caution in control of PC in commercial orchards; growers are advised to continue regularly monitoring border areas for accumulation of damage, maintain residual effectiveness of border treatments, and hope that the pool of available immigrant PCs is as sparse as it appears.
The International Dwarf Fruit Tree Association’s Annual Summer Tour is scheduled for June 24-27 in the Lake Champlain Valley of New York, Vermont, and Quebec. Each year IDFTA holds a summer tour in a prominent fruit production region throughout North America. In the past few years, IDFTA has been to Colorado, Virginia, and -- in 1997 -- right here in Massachusetts. The Champlain Valley is a striking fruit production area, with Lake Champlain surrounded by the Adirondack and Green Mountains of New York and Vermont respectively. Cool summers and crisp September weather make it the premier climate for growing the world’s best McIntosh apples. Cortland, Empire, and -- more recently -- Honeycrisp are also popular varieties.
Day 1 (Saturday) of the Tour will travel to Quebec with a couple orchard stops, including one that features the ‘Solaxe’ pruning and training system. A maple syrup operation, an African violet and orchid greenhouse, and a vegetable production and distribution operation will also be on the agenda. On Monday, IDFTA will travel to the New York side of the Lake, visiting the ‘world’s largest McIntosh orchard’ in Chazy, as well as other orchards in the Peru area. Cornell Cooperative Extension fruit specialists will be on hand to discuss recent research and establishment of dwarf tree demonstration plantings in these commercial orchards. A barbecue dinner at Shelburne Farms -- the world-famous restored mansion and farm of William and Lila (Vanderbilt) Webb -- will follow Monday¹s full day of orchard tours. On Tuesday, IDFTA will visit two orchards in the Shoreham, Vermont area, and will also tour a Cornell rootstock research planting in Crown Point, NY. And of course, no Vermont visit would be complete without stopping at Ben & Jerry’s premium ice cream plant in Waterbury, home also to Cold Hollow Cider Mill, New England’s largest fresh apple cider operation.
IDFTA Tour headquarters will be at the Sheraton Hotel in S. Burlington, VT. Pre-registration deadline is June 9. This will be an excellent opportunity to visit the Champlain Valley, learn about the local fruit industry, and pick up a few growing tips from fellow fruit growers from throughout North America. For more information, visit the IDFTA WWW site (www.idfta.org); call (413-323-4208) or e-mail (clements@umext.umass.edu) Jon Clements; or contact IDFTA business manager Charles Ax at 570-837-1551, attorney@ptdprolog.net.
Healthy Fruit is written by Dan Cooley, Ron Prokopy, Jon Clements, Starker Wright, Arthur Tuttle, Wes Autio, and Duane Greene except where other contributors are noted. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. A text version can be e-mailed to you if you contact Doreen York. Please cite this source if reprinting information.
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