Impact of corn earworm (Helicoverpa zea) on grain sorghum yields in Mississippi

The corn earworm, Helicoverpa zea(Boddie), is the most important insect pest of grain sorghum in most areas of the southern U.S. Recently, concerns have been raised about the validity of the current action threshold of one larva per panicle for this pest.  To address this, an experiment was conducted in Stoneville, MS utilizing artificial infestations with second instar corn earworms.  Larvae were infested at seven densities ranging from 0.17 to 6 larvae per panicle and compared to an uninfested control. Additionally, infestations were done at two plant densities.  Plant density did not have an impact on feeding injury or yield losses from corn earworm. Significant yield reductions compared to the uninfested control were observed for infestation densities of 0.5 or more larvae per panicle. These results suggest that the current threshold may be too high, but these data are preliminary and the experiment will be repeated in 2014.