Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

Abstract

Feeding punctures of the rice stink bug (RSB), Oebalus pugnax (F.), provide fungi entry sites into rice, Oryza sativa (L.), grains and kernels (hulled grains). Feeding sheaths also serve as a source of nutrients for fungi. Grain spotting fungi did not affect the percentage of spotted kernels (pecky rice) and significantly reduced full grain weight only at low infestation rates of one and two RSB per panicle. Panicles had been treated with a single application of propriconazol (1000 ppm) soon after flowering and later infested in the early milk stage with RSB adult pairs for 9 days. Propriconazol was not toxic to RSB adults. Infested rice lines were less susceptible to losses in full grain weight as panicles matured, but varied in the percentage of pecky kernels. Reductions in the number of full grains in medium and long-grain rice lines can be estimated using a 9% saline solution. The highest average rate of misclassification was 13.8% and these grains were pecky and immature. Resistance to RSB in rice lines can be compared by infesting panicles in the early milk stage (about 10 days after flowering) with three pairs of RSB adult pairs for 5 days. Either females, males, or pairs should be used consistently because females reduced the number of full grains more than males or pairs. Fifty-seven rice breeding lines, predominantly from the 1982 and 1983 foliar disease nursery, were evaluated for resistance to RSB injury. Seventeen lines had less than a 26% reduction in number and/or weights of full grains. The insecticides currently recommended for RSB control in Louisiana, encapsulated methyl parathion (0.3 kg AI/ ha), methyl parathion (0.3 kg AI/ ha), and Sevin XLR (1.1 kg AI/ ha), were re-evaluated. Encapsulation of methyl parathion extended activity for an additional day and this formulation was more toxic than methyl parathion to RSB in the first 24 hours of exposure. Carbaryl was active one day longer than the other insecticides, but all insecticides lost activity by 72 hours after application.

Pages

174

Share

COinS