Funded by an annual grant from the Northwest Center For Small Fruit Research Acknowledgments Biology and Control of Blueberry Gall Midge Chemical Trials Wei Q. Yang, 1 Lynell Tanigoshi, 2 Eduardo Chavez, 1 and Jason Harpole 1 1 Oregon State University, North Willamette Research and Extension Center, Aurora, OR 2 Washington State University, Northwestern WA Research & Extension, Mount Vernon, WA Introduction Abstract Objectives Since completing the initial blueberry gall midge (Dasineura oxycoccana Johnson) life cycle and finding no relationship between number of midges and shoot tip damages from , we concentrated our effort in determining the timing and insecticide application for its control. In 2006, the insecticides used were Mustang Max (0.025 lb(AI)acre), Admire (0.125 lb(AI)acre), and Platinum (0.5 lb(AI)/acre). In 2007, the same experiment was repeated, substituting experimental Brigade (0.1 lb(AI)/acre) for newly registered Mustang Max. The treatments with an untreated control were applied as a soil drench after fruit set and arranged in a randomized complete block design with each experiment unit consisting of a 40’ row of mature blueberries. Several soil traps were placed along the drip line of treated plots and yellow cards were hung on the trellis wire in each plot. Each week after insecticide application, traps and yellow card samples were collected to count number of adult gall midge fliers. Preliminary data analysis indicated all soil drench treatments resulted in good suppression of the emergence of midge adults in both years. In 2007, our modified soil trap seems to work better than the ones used in The new trap design will be displayed during the poster session. Field surveys conducted in Oregon and SW Washington from found that blueberry gall midge was present in all blueberry fields sampled. The damage caused by blueberry gall midge is primarily aborted and/or blackened young shoot tips as well as distorted developing leaves (h), which is often confused with boron deficiency. In heavily infested blueberry fields, a witches- broom like symptom may occur. It generally takes about 7-10 days for mature larvae to form puparia. The estimated time for the 1st larval instar to develope into an adult fly is about 2-3 weeks. There are multiple generations in a growing season with two main peaks of blueberry gall midge infestation. One peak is prior to harvest and the other after harvest. There is a dramatic decrease in infestation during harvest due to the lack of newly developed shoot tips during that time. Because the last generation of puparia overwinters in the soil, using an insecticide drench in early spring seems to be an effective way to reduce adult midge emergence. Determine the effectiveness of insecticide application used as a soil drench for controlling blueberry gall midge From this study, we feel it’s possible to significantly reduce the number of adult midge fliers emerged from soil with a soil drench application. The timing could be early spring before bud break. Controlling blueberry gall midge could be beneficial to young blueberry fields with heavy gall midge infestation, which could reduce young plant growth because of the repeated damage to growing shoot tips. Results Potential Significance to the Industry Yellow card samples were examined under a disecting microscope and the number of adult midge fliers was recorded with results shown in the graphs below. In 2006, Mustang Max, Admire, and Platinum all showed good control of midge adult emergence with Admire being the most effective. In 2007, Brigade, Admire, and Platinum again showed good control of midge adult emergence. All three insecticides seemed to have equal effectiveness in suppressing midge fly emergence from puparia in the soil. It was also clear that there were two peak midge emergences from the soil before harvest as shown by the hanging cards graph. The long suppressing period of all three insecticides was also noticed. Overall, all soil drench treatments resulted in good suppression of the emergence of midge adults in both years. The newly designed soil trap worked well for monitoring adult midge emergence from the soil and made the removal and replacement of the yellow cards very easy. Method Started in spring of 2006, a commercial blueberry field with heavy blueberry gall midge infestation was chosen to determine the effectiveness of soil drench with Mustang Max (0.025 lb(AI)acre), Admire (0.125 lb(AI)acre), and Platinum (0.5 lb(AI)/acre). Several soil traps were placed along the drip line of treated plots (each 40’ long). Treatments including an untreated check were arranged in a randomized complete block design. Sprays were applied using a commercial tractor driving soil surface sprayer with a spray width about 2 feet. In 2007, the same experiment was repeated, substituting experimental Brigade (0.1 lb(AI)/acre) for newly registered Mustang Max, while using a modified soil trap. Yellow cards were also hung in each treated plot. Cards were collected every 3-7 days. Future Direction We have noticed morphological differences of adult midge fly from the soil traps between spring and fall. It seems that the midge fly from early spring samples shared the same characteristic of blueberry gall midge. However the midge adult fly from the fall sampling did not appear to have the typical characteristics of a blueberry gall midge. We suspect there maybe differences in midge species in the northwest during a growing season. We plan to closely follow the morphological changes of adult midge fly next growing season to determine if there are more than midge species present. Picture descriptions : (a-c) Soil drench application in a commercial blueberry field. (d) Field traps and yellow cards were used for monitoring blueberry gall midge flies in 2007; (e) soil trap; (f) Yellow sticky cards hanging on the trellis wire; (g) Soil trap assembly; (h) Shoot tip damage by blueberry gall midge larvae; (i) Blueberry midge male fly. a b cd fe g h i