Issue link: https://read.dmtmag.com/i/466321
30 MARCH 1, 2015 GOOD FRUIT GROWER www.goodfruit.com Aphelinus mali, a tiny parasitoid wasp, appears resistant to most organophosphate insecticides, including diazinon, and seems to tolerate single applications of some neon- icotinoids midseason without flareups, he said. Almost as important in controlling WAA in the mid-Atlantic are several species of syrphid fly larvae. "Other generalist predators such as green and brown lacewings, minute pirate bugs, and some lady beetles may prey on WAA colonies when the nymphs and colonies are still small and unprotected by the waxy white coating and white filaments that protect larger nymphs and adults," he said. Here are Biddinger's guidelines and control strategies for minimizing the impact on biological control while still giving acceptable management of woolly apple aphid: —Use resistant rootstocks if possible. WAA feeding on roots is especially harmful to smaller dwarf trees. Keep a close eye on what appear to be varieties favored by the pest, such as Fuji, Rome, Greening, York, and Ginger Gold. —Conserve biological control if possible. The Pennsylvania Tree Fruit Production guide contains ratings of various pesticides' impact on A. mali and syrphids. —Avoid pyrethroids, including combination products like Endigo (lambda- cyhalothrin and thiamethoxam), Lannate, and the insect growth regulator Rimon (novaluron), which consistently flare WAA. —Use Delegate (spinetoram) for first generation codling moth, but use Altacor (rynaxypyr) or Belt (flubendiamide), which won't affect WAA biological control, for second generation. —Avoid multiple applications of neonicotinoid insecticides after June and try to restrict use to products that are "softer" on beneficials, which include Calypso (thiaclo- prid), Assail (acetamiprid) and Provado (imidacloprid), at lower-than-maximum rates. Multiple applications of all products other than Calypso can also affect mite biological control, he said. "For late season control of BMSB, neonicotinoids are the least disruptive control options, but we have seen evidence that at least Belay (clothianidin) may flare mites the following season," Biddinger said. "Depending on the timing, these sprays may also affect WAA biocontrol, but in general, sprays after mid-September probably don't have much effect, as WAA populations have crashed at this point and the biocontrol agents are moving to overwintering sites." —Diazinon is the most effective and cheapest product for control of WAA, he said. It is the only labeled use for this product and only a single application is allowed or nec- essary. "If you also have San Jose scale (SJS) in your orchards, Movento (spirotetramat) will control both pests even if you timed the spray early in the season (around first cover) for SJS crawlers," he said. "When used with a penetrant adjuvant or oil, Movento has proven very effective in controlling both pests, albeit at a much higher cost than diazinon. None of the neonicotinoids have proven effective on WAA."