DAMAGE FUNCTION-ANALYSIS FOR THE RICE STINK BUG (HEMIPTERA, PENTATOMIDAE)

The effect of the rice stink bug, Oebalus pugnax (F.), on rough rice y ield, head yield, and peck was investigated during 3 yr of experiments at Beaumont and Eagle Lake in the Texas Rice Belt. Natural infestatio ns of rice stink bugs were manipulated by varying planting date and ap plying control measures at selected rice grain maturation stages. Data were subjected to linear, quadratic, and square root functions to obt ain best-fit relationships. Damage functions were characterized as nes ted or nonnested models to facilitate statistical test selection. Nest ed models were statistically evaluated using the Schwarz criterion; no nnested models were subjected to the Cox test. In the case of peck, da mage that manifests itself as discolored spots on the rice kernel and thus reduces quality, we detected no statistical differences in explan atory power between a model including both nymphs and adult rice stink bugs and a model with only adult rice stink bugs. Head yield (the per centage of whole grains after milling) was not affected by nymphal pop ulations. Linear models best fit the damage relationships between adul t rice stink bug densities at various grain maturation stages. Peck va ried across grain maturation stages, with a low of 0.019% in milk to a high 0.033% in hard dough per observed adult rice stink bug. Data als o suggest that a significant level of peck was unaccounted for by rice stink bug populations in the milk and later grain maturation stages, indicating monitoring of rice stink bug populations should begin durin g panicle exsertion. Rough rice yield was not affected by nymphal or a dult rice stink bug populations encountered in the experiments.