Issue link: http://read.dmtmag.com/i/466321
www.goodfruit.com GOOD FRUIT GROWER MARCH 1, 2015 29 MAKE the MOST of biocontrol by Richard Lehnert B enefi cial insects and mites can play a role in controlling key orchard pests if they're not exposed to harmful pesticides. Dr. David Biddinger, entomologist with Pennsylvania State University in Biglerville, explains how to take advantage of biocontrols for managing mites, woolly apple aphid, and scale. Mites In apple orchards, the predatory mite, Typhlodromus pyri, is a major force controlling European red mites. "Mite fl are-ups come from either the loss of predators such as T. pyri or a growth hormone-like stimulatory effect, called hormolygosis, caused by pyrethroids and some neonicotinoid insecticides," Biddinger said. The insecticides are like steroids for the mites. "Hormolygosis can cause pest mites to have more gen- erations in a year and, more importantly with late season BMSB sprays, cause the fall mite females to lay many more overwintering mite eggs than normal. When these mite eggs hatch around bloom time the next spring, even if predatory mites have survived the sprays, they can't increase fast enough to keep up with all the spider mites at petal fall to fi rst cover." Hormolygosis is now thought to be the major cause of mite fl areups. Biddinger recommends growers battling European red mite and two-spotted spider mite stop using pyre- throids if possible. Substitute a neonicotinoid such as Venom/Scorpion and Actara (thiamethoxam) if preharvest intervals allow. If a summer miticide is needed, use a selective one such as Envidor (spirodiclofen), Nealta (Cyfl umetofen), and Zeal (etoxazole) as complete sprays rather than alternate-row-middle sprays. Other miticides are toxic to T. pyri. "Recent trials have shown that Agri-Mek (abamectin) plus oil at petal fall plus seven-day timing generally gives seasonal control of mites without hurting the predator mites," Biddinger said. "The disadvantage is that you have to treat generally before you know you have a prob- lem, which is against the principle of biological control. On the other hand it is cheap and effective. It can help you to bring pest mite populations back into equilibrium with predatory mites for the next season if you have been using harsh pesticides in the past for BMSB or mitigate the effects of mites, at least if you are still using them." Woolly apple aphid Parasitic wasps and fl ies help control San Jose scale and woolly apple aphid. Woolly apple aphid is not an invasive insect. "It is one of America's unique con- tributions to the worldwide apple pest community," Biddinger said. This "made in the USA" label gives something of an advantage when it comes to biological control, he said.