|Arthur, Franklin - Frank|
Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2003
Publication Date: 9/1/2004
Citation: Arthur, F.H., Yue, B., Wilde, G.E. 2004. Susceptibility of stored-product beetles on wheat and corn treated with thiamethoxam: effects of concentration, exposure interval and temperature. Journal of Stored Products Research 40:527-546. Interpretive Summary: Treated seed stored in bags is subject to attack from stored-grain insects, but these insects are often overlooked in testing programs because of the emphasis on seed protection against field crop pests. Thiamethoxam (Adage) is a new seed treatment being developed for commercial use, but there is no information regarding the susceptibility of stored-grain beetles. We evaluated this chemical against common pests of stored corn and stored wheat, and found it to be very effective at low application rates. The rates needed to control adult beetles were far lower than those previously reported for moth larvae. Results show thiamethoxam would be an effective seed treatment for stored-grain beetles.
Technical Abstract: Sitophilus zeamais Motschulsky, the maize weevil, Oryzaephilus surinamensis L, the saw-toothed grain beetle, and Tribolium castaneum Herbst, the red flour beetle, were exposed for 1, 2, 3, and 6 days at 22, 27, and 32°C on corn treated with 0, 0.5, 1.0, 2.0, or 4 ppm thiamethoxam, a new- generation neo-nicotenoid insecticide. A second series of tests was conducted on hard winter wheat using S. oryzae L., the rice weevil, Rhyzopertha dominica (F.), the lesser grain borer, and T. castaneum. Mortality of all species on both commodities generally increased with concentration, exposure interval, and temperature, and data were described by linear and non-linear regressions with concentration as the independent variable. Mortality of S. zeamais ranged from 58 to 90% on corn treated with 0.5 ppm thiamethoxam, and approached 95 to 100% as concentration increased to 4 ppm. O. surinamensis appeared to be slightly less susceptible than S. zeamais; mortality ranged from about 18 to 80% at 5 ppm and there was a more gradual increase in mortality as concentration increased. Mortality of T. castaneum generally did not exceed 40% on any concentration unless the beetles were exposed for 6 days. Mortality of R. dominica and S. oryzae was less than 60% when exposed on treated wheat for 1 and 2 days, but increased to nearly 100% when exposed for 6 days at 27 and 32°C. Mortality of T. castaneum did not exceed 20% at the 1 and 2-day exposures, and approached 100% only when beetles were exposed for 6 days at 32°C. Few F1 adults of any species were found in treated corn or in treated wheat, however, the number of F1 T. castaneum in untreated corn and untreated wheat was very low compared to the other species. Results show that thiamethoxam would be an effective protectant of stored corn seed and stored wheat seed.