Good Fruit Grower

May 15

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Page 30 of 55 GOOD FRUIT GROWER MAY 15, 2014 31 Cherries Michigan growers WARY OF SWD A trapping program is vital so growers know where the spotted wing drosophila is and when. by Richard Lehnert Larry Gut M ichigan growers of berries of all kinds have been hammered by spotted wing drosoph- ila since the invasive fruit fly was first found in the state in 2010. Grapes and peaches are also targets, and so are cherries, somewhat. "With cherries, we're on the borderline of getting into trouble," said Michigan State University entomol- ogist Dr. Larry Gut. He's been part of Michigan's SWD Response Team that includes several fruit entomologists who run a trapping program to monitor timing of emer- gence, egg laying, and fruit infection, and investigate ways to prevent damage. "We found none in the fruit before harvest last year," Gut said about spotted wing drosophila in cherries. In Michigan, tart cherries and sweet cherries for brining are harvested once-over with shakers and catching frames, mostly during July. Fruit left on the trees after harvest are infested shortly after insecticide applica- tions stop. Growers have to spray until close to harvest to protect fruit from cherry fruit flies, and that probably controls spotted wing drosophila as well, if they choose the right insecticides. Gut has been evaluat- ing those for efficacy and has a list of those that do the job. Michigan's approach to this new, invasive fruit fly has been to trap to know where it is and when, keep grow- ers informed, evaluate insecticides to find good controls, and hope for break- throughs that will tame this insect. Oregon State University entomologists— Peter Shearer and others—traveled to South Korea and collected five species of parasitoid wasps that are being raised in quarantine at the University of Califor- nia, Berkeley. "One of them appears to be a specialist on SWD," Gut said. It makes it easier to obtain a release permit if the parasitoid attacks only the target species. Some target larvae, others pupae. Unlike ordinary fruit flies, spotted wing drosoph- ila females can force their way into unripe fruit with a sawlike ovipositor. They don't need to wait for the fruit to get overripe and soft. Females live about nine weeks and lay up to 300 eggs that hatch into small, white worms. Gut noted that cherries become attractive to the flies when color starts to change. Gut has also noted that spotted wing drosophila seems to emerge later in the summer if weather has been harsh the previous winter. Since it was quite cold in Michigan on sev- eral occasions last winter, Gut is pre- dicting a later emergence this coming summer. Cherry growers may con- tinue to stay on the right side of the borderline. Last year, spotted wing drosophila emerged in southwest Michigan July 15 and July 23 in northwest Michigan, where both sweet and tart cherries are grown. By those dates, harvest is usually just about complete. Monitor with traps Michigan State University has developed a Web site,, with sev- eral pages devoted to spotted wing drosophila, includ- ing weekly reports that start in mid-June and continue through August. In addition to 60 trapping sites moni- tored by the MSU entomologists, Gut is urging growers to monitor their orchards with traps. "Because SWD reproduces so quickly under optimum conditions, the first catch information is vital to activate pest management programs to prevent rapid population increases and potential infestations in a region," said Dr. Nikki Rothwell, coordinator of the Northwest Michigan Horticultural Research Station and a participant in the trapping program. When temperatures get about 65 to 70 degrees, gener- ation times can be as short as 12 days, she said. Gut and the MSU team have been experimenting with traps trying to find those that are very sensitive and will pick the flies up early. The flies are attracted to vinegar, so a common trap has been a clear plastic cup baited with vinegar. An improved trap was one baited with yeast and flour. It attracted more flies but smelled "so horrible," Gut said, it was hard to get the technicians to take the flies out to identify and count them. Only the males have the characteristic spots on their wings; females must be identified from their serrated ovipositors. This last year, Gut's MSU colleagues tested a lure from Trécé made with a blend of volatiles and a soapy water drowning solution, which worked even better and caught more flies—and smelled much better. In tests conducted across the country, researchers found that the insecticides that worked best against spot- ted wing drosophila included Imidan (phosmet), Dele- gate (spinetoram), Mustang Max (zeta-cypermethrin), Danitol (fenpropathrin), and Lannate (methomyl). Mal- athion, Brigade/Bifenture (bifenthrin), and Hero were a step lower, but still "very effective." Sevin (carbaryl) was less effective. PyGanic (pyrethrins) and Assail (acetami- prid) were weak to fair, and Entrust (spinosad) rated good, but these three have short residual effect. Some newer materials are being tested, and work quite effectively, Gut said, but are not yet labeled. • Spread of spotted wing drosophila Newly detected Previously detected 2008 2009 2010 2011 2012 2013 SOURCE: The Boston Globe and Hannah Burrack, NCSU Spotted wing drosophila insecticide rankings Excellent 4 Good 3 Fair 2 Weak 1 No activity 0 Actara Assail AzaSol Brigade Danitol Delegate Entrust Exirel Imidan Lannate Malathion Mustang Max Provado Pyganic Rimon Sevin Sivanto Most effective: Imidan, Delegate, Mustang Max, Danitol, Lannate Very effective: Malathion, Brigade/Bifenture, Hero Shorter residual: Entrust, Pyganic, Assail SOURCE: Michigan State University "The first catch information is vital to activate pest management programs to prevent rapid population increases." —Dr.Nikki Rothwell

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