STINK BUGS ON GRAIN SORGHUM IN MISSISSIPPI:ECOLOGICAL RELATIONSHIPS WITH HOST PLANTS AND CROP PLANTING DATES AND CROP DAMAGE

by Parada, Mario E.

This study was conducted to determine infestation levels of southern green stink bug, Nezara viridula (L.), and green stink bug, Acrosternum hilare (Say), on host plants including corn, cotton, soybean, sorghum, and non-crop vegetation in a multicrop ecosystem. Stink bug infestations responsible for crop damage on vegetative and panicle stages of grain sorghum planted on different dates were also investigated. Both N. viridula and A. hilare appeared to establish a first generation on non-crop grasses surrounding cultivated fields and then moved to soybean or cotton to begin a second generation. These stink bugs did not appear to be attracted to corn or sorghum when cotton and soybean were in attractive growth stages in the same ecosystem in this study. A large population of N. viridula infested soybean during R5 (beginning seed) to R7 (beginning seed maturity) plant growth stages. Sorghum planted in May was not infested with stink bugs, whereas sorghum planted in mid- to late June or early to mid-July was infested with a large numbers of N. viridula, but not A. hilare. Movement of N. viridula from soybean to sorghum coincided with attractive reproductive stages of sorghum. Southern green stink bugs caused significant damage to sorghum when panicles were caged and infested from milk stage to seed maturity or from soft-dough stage to seed maturity with 4 adults or 10 nymphs per panicle. No reductions in seed weight or seed germination were found when 5 adults were confined on sorghum panicles during hard-dough to seed maturity. These data would suggest that economic thresholds for N. viridula under conditions of this study were 3 adults or 6 to 9 nymphs per panicle for sorghum in milk stage to seed maturity. The reductions in seed weight and seed germination were associated with the number of stink bugs per panicle and the stage of seed development.