Good Fruit Grower

March 1

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Page 30 of 47 Good Fruit Grower MARCH 1, 2016 31 Danger from SWD? Researchers are concerned that rising spotted wing drosophila numbers could cause problems for sweet cherries. by Leslie Mertz R esearchers hypothesized early last year that spotted wing drosophila populations wouldn't reach high enough levels by mid- July to impact the tart cherry harvest in Michigan, but they did: Loads of fruit were rejected, dumped or juiced. Could the same thing happen to Michigan sweet cher- ries in 2016? That was the question posed by extension specialist Nikki Rothwell, coordinator of the Northwest Michi- gan Horticulture Research Center, during a talk at the December Great Lakes Fruit, Vegetable and Farm Market EXPO. Rothwell explained that although SWD didn't experi- ence an exponential increase until August, populations did undergo an earlier-than-expected rise in July and therefore had an impact on tart cherries. Her concern is that SWD numbers could reach a critical point even sooner and cause a similar problem for sweet cherries, which are harvested about 10 to 14 days earlier than tart cherries. In addition, she noted research that has found sizable numbers of SWD larvae in wild-growing, noncrop hosts adjacent to commercial blocks of both tart and sweet cherries (see "Searching for spotted wing drosophila" at left). This included Michigan studies showing heavy pop- ulations of SWD larvae in mulberry and honeysuckle in mid- to late-July, which coincides with late sweet cherry harvest. Traps in those noncrop hosts, however, were catching no adults at that time, suggesting that adults had already migrated to other hosts, including cherries. "These data, to me, indicate that we do have potential to have infestation in sweet cherries," she said. Rothwell said, "SWD adults are successfully reproduc- ing in many noncrop hosts adjacent to sweet cherries, but (as of 2015) they were not building populations early enough to cause problems in commercial sweet cherry orchards." That said, she asserted that if mated females are reproducing successfully in noncrop hosts next to orchards just a bit earlier in the season, "it's not a long flight to be moving into your commercial blocks." Rothwell and other extension agents will be keeping a close watch on SWD in 2016 to gain a better understand- ing of the fly's population arc, its migration from non- crop hosts into cherries, and possible control measures, including the removal of host plants from the orchard's periphery and the best timing for pesticides. She said she hopes these efforts will provide needed guidance as growers in the state adjust to this intensifying pest. • A new standard in spotted wing drosophila detection • Early detection in low population density • Superior attraction in wide range of crops and locations • Extended field life • Scentry SWD Lure performed better than competing lure systems in recent field trials SWD LURE & TRAP SOLUTION Source: Dr. Elizabeth H. Beers, 2014 WSU-TFREC Trece™ is a trademark owned by Trece, Inc. Contact your local distributor or call 1-800-735-5323 Visit our website,

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