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6 MARCH 1, 2016 Good Fruit Grower www.goodfruit.com Study shows apple maggot pupae can be killed in yard waste, but more research is needed. by Shannon Dininny A pple maggot pupae in yard waste piles can be killed by insulating and heating the piles, according to a preliminary study, but experts say the results, while promising, require more research to ensure the pests will not survive to infest commercial apple orchards. Apple maggot began appearing in the Northwest in the 1980s, which is when state officials began imposing quarantines to prevent it from infesting commercial orchards. The pest has proliferated in backyard fruit trees in urban areas that are now looking to compost yard waste in a bid to recycle more and save landfill space. Washington officials issued permits to several compa- nies allowing them to transfer yard waste to composting facilities in pest-free zones, despite concerns from the industry that the pest could ride along. But when apple maggot turned up in a trap near one last year, they halted the practice until more research could be done to deter- mine the risks to the state's $2 billion apple industry. Apple maggot has never been found in commercial fruit in Washington, yet it is a key pest of concern to some trading partners. Heating the pupae Last fall, Dr. Wee Yee, research entomologist at the USDA's Agricultural Research Service laboratory near Wapato, Washington, began researching cost-effective ways to kill pupae in yard waste piles, with the idea being to kill pupae at the source before yard waste is transferred to a pest-free zone. Little research has been done on effective methods to kill apple maggot pupae, Yee said during an evening pre- sentation at January's Apple Crop Protection Research Review in Wenatchee, Washington. A 2008 study showed that apple maggot larvae do not survive rearing at 104°F or hotter, so Yee elected to apply heat in his own labo- ratory tests on pupae. He found that 100 percent of the pupae died after three days when heated to 122.9°F. He moved on to field tests last fall at the Terrace Heights Landfill east of Yakima, Washington. Yee built yard waste piles composed of 30 cubic yards of waste, with 60 to 65 percent moisture content, which is ideal for composting. Organdy bags each holding between 18 and 31 pupae were inserted into the piles — on the surface of the pile, at 5 centimeters deep and at 46 centimeters deep — with data loggers next to the bags registering the temperature over the course of the study. Apple maggot in YARD WASTE Apple maggot life cycle Apple maggot overwinter as pupae in the soil. Adults emerge in early summer, peaking in July, and once mature, females lay eggs under the skin of apples. The eggs hatch and the larvae feed within the apple, passing through three instars before the infested fruit falls to the ground and the larvae leave the fruit to burrow into the soil, molt into a fourth instar and overwinter as pupae. In Washington, apple maggot was first detected in 1980 in Clark County in the southwest part of the state. Today, apple maggot is present in at least 22 of Washington's 39 counties, though much of the commercial apple production region remains pest-free. Pest Management Continued on page 8 TECH-FLO ® ZETA ZINC 22 ASK YOUR P.C.A. OR CALL NUTRIENT TECHNOLOGIES TOLL-FREE: 877/832-4356 FOR THE DEALER NEAREST YOU. Just because you put a foliar zinc on doesn't mean the job's done. Some zinc products are so ineffective they are better suited as sun- screens or paint. In trial after trial, TECH- FLO ® ZETA ZINC 22 (22% Zinc) has been shown to be the most effective foliar zinc product on the market today, getting the zinc into the tree where it is needed. For the best value for your nutritional dollar, choose TECH-FLO ® ZETA ZINC 22. UNSURPASSED FOLIAR ZINC PERFORMANCE! …PUTTING ZINC ON PUTTING ZINC IN… PUTTING ZINC IN…