Fourth International Bemisia Workshop International Whitefly Genomics Workshop
Impact of Insecticide Residue on Bemisia tabaci (B-Biotype)
1 Texas Cooperative Extension, Overton, TX, USA. Correspondence: swludwig@ag.tamu.edu
2 U. S. Horticultural Research Laboratory, Fort Pierce, FL, USA
In 2005, the Q-biotype of Bemisia tabaci was identified in the United States. This finding and increased problems with management of the B-biotype of Bemisia tabaci have resulted in a national effort to develop a comprehensive management plan for whiteflies on ornamental crops. The objective of the following study is to evaluate the activity of insecticide residue against silverleaf whiteflies to aid in the development of a whitefly resistance management program. Three studies have been conducted evaluating pesticide residue on poinsettia plants (Freedom Red) against B. tabaci biotype B. In the first study we evaluated pesticide residue at three time intervals after a single foliar application to poinsettia plants. The following treatments were evaluated at labeled rates: Judo (spiromesifen), Avid 0.15EC (abamectin), Sanmite 75WP (Pyridaben), Enstar II (S-kinoprene), Endeavor 50WG (pymetrozine), Distance IGR (pyriproxyfen), and an untreated control (see Table 1 for rates). Clip cages were placed onto leaves at 7 hrs, 8 days, and 14 days after application. These leaves were fully expanded when the plants were treated. Ten adult whiteflies of mixed sex and age were then placed into each cage. After 48 hours the number of eggs and dead whiteflies were recorded. Eggs were allowed to hatch, nymphs develop, and adults emerge. The number of emerged adults was then recorded. Similar procedures were followed in the second and third experiments, except the trials conducted for longer time periods. In the second trial the following neonicotinoids were evaluated as drenches: imidacloprid, clothianidin, dinotefuran and thiamethoxam. In the third trial the following neonicotinoids were evaluated as foliar sprays: imidacloprid, clothianidin, dinotefuran, thiamethoxam and acetamiprid. Results from all three trials will be presented at the meeting. Data were transformed using an arcsine transformation prior to analysis. Data were analyzed with ANOVA and means separation was accomplished by using the least significant difference test (LSD) at the P<0.05 level. All data are presented as original means. No insecticide provided greater that 70% direct adult mortality (Table 1). Distance provided 100% control of the resulting generation on all sample dates (Table 2). Judo provided greater than 80% control of the resulting generation on all sample dates. Avid provided greater than 90% control for the first two sample periods. The other insecticides have varying levels of residue activity. These results indicate that none of the products evaluated will give effective control of adults once the insecticides have dried. However, Distance, Judo and Avid provided excellent immature whitefly control for 10 days while Distance and Judo provided an additional 6 days of excellent and good control, respectively. Sanmite managed to kill over 60% of the nymphs during the periods evaluated. This trial will be repeated and additional trials are planned to evaluate the residual activity of other insecticides used to manage whiteflies. These results will enable grower and extension personnel to better understand the residual activity of insecticides. This will, in turn, result in better insecticide rotation programs for the management of whiteflies.