Good Fruit Grower

March 1

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10 MARCH 1, 2016 Good Fruit Grower Pest Management P ests posed a challenge to some grow- ers in the record heat of 2015, but the heat presented an opportunity for researchers to learn more about how best to control two of them — codling moth and obliquebanded leafroller — when temperatures are high. Dr. Vince Jones, entomologist at Washington State Univer- sity's Tree Fruit Research and Extension Center in Wenatchee, Washington, compared 2015 temperatures to those of a simi- lar high-temperature year, 1958. The result: Summer was not hotter, but spring and fall were warmer, creating additional degree-days at key times and enabling an additional genera- tion of both codling moth and leafroller. "It's not just the total degree- day accumulation that's important; it's when the degree-day accumulation occurs," Jones told growers at the Washington State Tree Fruit Association Annual Meeting in December. The hotter year overall means more cod- ling moth generations will occur and higher numbers will emerge in 2016. The warm fall also means more larvae that escaped diapause (the dormant stage that overwinters) in August would still make it successfully to the over- wintering stage, which is true for both codling moth and leafroller. These factors could make control diffi cult for growers again, and forecasters are predict- ing 2016 will be another hot year, Jones said. Codling moth For roughly the past 50 years, growers have generally applied two sprays per generation to control codling moth in a year with average temperatures. The fi rst spray occurs at 3 per- cent to 5 percent egg hatch — or roughly 425 degree-days — followed by a second spray 14 days later. Following research by WSU entomologist Jay Brunner, some growers began using a delayed fi rst cover approach to target the fi rst and second generations. The idea is to put oil on just before egg hatch at 375 degree-days, then a second larvicide spray at 525 degree- days and a third spray 14 days later. Organic growers can follow the same method but sub- stitute organic materials. In 2015, Jones tested those treatments to determine effi cacy in a warm year. He found that pesticide treatments alone have roughly the same effectiveness as in a cooler year. "It's not to say they didn't work well, but remem- ber, you have another generation to fi ght," he said. However, adding a delayed fi rst cover made the applications twice as effective overall and cut the codling moth population by half. "Unless you miss that fi rst window, you really should be using this delayed first cover in almost every circumstance," he said. Jones also found that all of the codling moth treatments worked better when paired with mating disruption. "Even a weak treatment program is better with mating disruption than a good, conventional plan without it," he said. And there's a bonus: Conventional codling moth treatments can also reduce incidence of obliquebanded leafroller by about 70 percent. He advised growers to keep a close tab on Pests in the HEAT Last year's hot growing season gave researchers ideal opportunity to take a closer look at codling moth and obliquebanded leafroller. by Shannon Dininny "Even a weak treatment program is better with mating disruption than a good, conventional plan without it." —Vince Jones

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