Issue link: https://read.dmtmag.com/i/466321
www.goodfruit.com GOOD FRUIT GROWER MARCH 1, 2015 11 In one swift stroke, Gladiator® insecticide/ miticide provides control of the top three citrus pests with two chemistries in an easy-to-use formula. Throughout the season, victory over pest pressure will be yours. To start reaping the benefi ts of Gladiator call your FMC Star Retailer call 888-59-FMC-AG or visit FMCcrop.com. A DEVASTATING STRIKE TO PSYLLIDS, LEAFMINERS AN D MITES. Diet tests Schmidt-Jeffris, who is working with Dr. Elizabeth Beers, did lab studies to compare the two predatory mites. She found no important differences in the life stages of the two species. However, they did have different food prefer- ences. When served only eggs of the two-spotted spider mite, A. caudiglans ate more than did G. occidentalis. Both enjoyed spider mite protonymphs equally. But then Schmidt-Jeffris found that A. caudiglans stopped laying eggs when it was only fed two-spotted spi- der mites and concluded that it was not an ideal prey. It prefers European red mite, which produces less webbing than McDaniel or two-spotted spider mites. She then asked managers of the orchard blocks she had sampled to fill out an online survey with information on the apple varieties grown, age of the block, management practices, pesticide use, prey available, and surrounding landscape. Where Acramite (bifenazate) and conventional pesticides were used, G. occidentalis was more plentiful. In low-input and organic blocks and those with an abundance of grass or weeds in the tree row, A. caudiglans fared better. Schmidt-Jeffris said she was not sure why A. caudiglans liked weeds. It's possible they provided shelter or additional resources for the mite, or it might survive better where herbicides are not used. A. caudiglans was less plentiful in Golden Delicious trees, which have smoother leaves than other varieties. Some predatory mite species prefer varieties with hairier leaves that are easier for them to cling to and reproduce on. Pesticides Laboratory bioassays with eight orchard pesticides showed that G. occidentalis was fairly tolerant of most pesticides except for Provado (imidacloprid) and Delegate (spinetoram) whereas A. caudiglans was sus- ceptible to more pesticides, including Acramite, Sevin (carbaryl), Provado, and Delegate. Though Guthion (azinphos-methyl) can no longer be used, it was included in the test for comparison and proved to be much more toxic to A. caudiglans than to G. occidentalis. Although Acramite is labeled as being safe for ben- eficial insects, including predatory mites, it killed 44 percent of the A. caudiglans mites. It had no effect on G. occidentalis, however. "Don't assume that what's good for one predator will be good for the other predator," Schmidt-Jeffris said. • Galendromus occidentalis, formerly known as Typhlodromus occidentalis, is the most commonly found predatory mite in Washington. Amblydromella caudiglans eats a two- spotted spider mite.