Submitted to: Insect Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2008
Publication Date: 11/30/2008
Publication URL: http://hdl.handle.net/10113/28912
Citation: Chanbang, Y., Arthur, F.H., Wilde, G.E., Throne, J.E. 2008. Control of Rhyzopertha dominica (F.) in stored rough rice through a combination of diatomaceous earth and varietal resistance. Insect Science. 15(5): 455-460. Doi: http://dx.doi.org/10.1111/j.1744-7917.2008.00233.x. Interpretive Summary: Different varieties of grain crops, including rough rice, vary in their susceptibility to stored-product insect pests. We conducted a test by exposing adult lesser grain borers, a major insect pest of stored grains, on susceptible and resistant varieties of rough rice treated with increasing rates diatomaceous earth (DE). The production of offspring from these exposed adults was assessed as a measure of control. As the rate of DE increased to the maximum rate specified on the insecticide label, few offspring were produced on 3 of 4 resistant varieties. In contrast, more offspring were produced on the 4 susceptible varieties. There was also a corresponding increase in the percentage of insect-damaged kernels in the susceptible varieties compared to the resistant varieties. Results show that combining natural varietal resistance with a reduced-risk insecticide such as DE could limit lesser grain borer populations and result in less damage to the commodity.
Technical Abstract: Adults of Rhyzopertha dominica (F.), the lesser grain borer, were exposed on four varieties of rough rice each with low (Jupiter, Bengal, Wells, Progue) and high (Rico, M-205, Akita, and Cocodrie) Dobie indices of susceptibility, and treated with varying rates of the commercial diatomaceous earth (DE) Insecto®. Mortality of parental R. dominica on untreated rough rice of the varieties Jupiter, Bengal, Wells, and Pirogue (hereby termed “resistant”) ranged from 5 to 52.5% compared to less than 4% mortality on the untreated rough rice from varieties Rico, M-205, Akita, and Cocodrie (hereby termed “susceptible). Adult mortality increased as the rate of DE increased from 0 to 1,000 ppm, and was greater on the resistant than the susceptible varieties. At the greatest concentration of 1,000 ppm DE, mortality of R. dominica on all resistant varieties except for Pirogue was 97 to 100%, but ranged from 46.2 to 74.2% on Pirogue and the susceptible varieties. Progeny production from the parental generation exposed on the rice treated with 1,000 ppm DE ranged from 0-22 adults on the resistant varieties and from 30-105 adults on the susceptible varieties. Percentage of IDK on the rice treated with 1,000 DE was less than 1% on the resistant varieties Wells, Bengal, and Jupiter, but was greater than or equal to 3% on the other varieties. Results of this test showed that suppression of R. dominica populations with DE was enhanced on three of the four varieties of rough rice that were considered to be resistant to R. dominica.