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Title: Influence of growing location and cultivar on Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) infestation of rough rice

item Arthur, Franklin

Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2007
Publication Date: 5/30/2007
Citation: Arthur, F.H., Bautista, R.C., Siebenmorgen, T.J. 2007. Influence of growing location and cultivar on Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) infestation of rough rice. Insect Science 14: 231-239.

Interpretive Summary: The location where a grain crop is grown, the specific cultivar, and the internal physical characteristics of the grain kernel will often affect susceptibility to stored-grain insects. We exposed adult lesser grain borers and rice weevils on several cultivars of long-grain and medium-grain rice from several growing locations. Progeny production of both species and resultant feeding damage varied with both rice types and with the specific cultivar and location, but the physical characters we measured were not correlated with progeny production. Location and cultivar were important in determining the susceptibility of rough rice to the lesser grain borer and the rice weevil, but this susceptibility probably relates more to the condition of the exterior hull than the physical characteristics of the kernel itself.

Technical Abstract: Long-grain rice cultivars Cocodrie, Wells, and XP 723 grown in three locations, and medium-grain rice cultivars Bengal and XP 713 grown in two locations, were harvested and assayed for susceptibility to Rhyzopertha dominica (F.), the lesser grain borer, and Sitophilus oryzae (L.), the rice weevil, on rice held at 27°C, and 57 and 75% relative humidity (r.h.). Separate samples from the same harvest lots were also analyzed for the physical characteristics of brown rice yield, % whole kernels, and kernel thickness. Progeny production and feeding damage of R. dominica were significantly different among long-grain cultivars within two of the three locations (P < 0.05), but not for location or r.h., while progeny production of S. oryzae was different among cultivars, location, and r.h. On medium-grain rice, both cultivar and location were significant for progeny production of R. dominica, but not r.h., while cultivar and location were significant for progeny of S. oryzae, but not location. On both rice types, feeding damage of R. dominica followed the same trends and was always strongly positively correlated with the number of progeny, but for S. oryzae there were several instances in which progeny was not correlated with feeding damage. Although there were significant differences in physical characteristics of both rice types, actual numerical differences were extremely small and therefore may not be biologically significant. The physical characters measured were generally not correlated with progeny production of either species. Results indicate that the location and cultivar influence susceptibility to R. dominica and S. oryzae, but this susceptibility may be related to intrinsic differences among cultivars and conditions that affect the condition of the exterior hull or husk, rather than physical characteristics of the kernel.