Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2006
Publication Date: 10/1/2007
Citation: Chanbang, Y., Arthur, F.H., Wilde, G.E., Throne, J.E. 2007. Efficacy of diatomaceous earth and methoprene, alone and in combination, against Rhyzopertha dominica (F.) (Coleoptera: Boxtrichidae) in rough rice. Journal of Stored Products Research. 43(4): 396-401. Doi: http://dx.doi.org/10.1016/j.jspr.2006.12.003. Interpretive Summary: Diatomaceous earth (DE) is a natural inert dust registered for insect control, but it does not give compete control of the lesser grain borer, a major insect pest of stored rough rice. The insect growth regulator (IGR) methoprene will limit progeny of lesser grain borer but will not kill adults. We combined both products using different application rates on long grain, medium grain, and short grain rough rice. Mortality of adults was only 60% at the label rate of DE, and there were differences among the rice types. However, when methoprene was included in the insecticide treatment, no offspring were produced. Results show that methoprene by itself will eliminate progeny production of the lesser grain borer, but the addition of DE will give some control of adults and could limit damage from adult feeding.
Technical Abstract: Combination treatments of diatomaceous earth (DE) (Protect-It) and the insect growth regulator (IGR) methoprene (Diacon II) were evaluated against Rhyzopertha dominica (F.), the lesser grain borer, on stored rough rice. Application rates of DE and methoprene ranged from 0 to 500 ppm and 0 to 1 ppm, respectively, in 25 treatment combinations. Tests were conducted by exposing parent adults for two weeks at 32 degrees C and 75% relative humidity on single varieties of long grain, short grain, and medium grain rice, removing adults, and holding the rice for eight weeks at the same conditions to collect F1 progeny. With DE alone, mortality at the highest rate of 500 ppm was only about 60% in long and medium grain rice, and 25% in short grain rice. Diatomaceous earth did not give complete control of R. dominica on rough rice in this test; however, the differences among rice varieties seems to indicate that the specific type and possibly variety of rough rice may influence mortality and reproduction of R. dominica exposed to DE. Any concentration of methoprene completely suppressed F1 progeny in all three varieties of rough rice. Results indicate that methoprene alone would limit progeny production of R. dominica on rough rice.