The Effect of Lygus and Hyaline Grass Bugs on Lettuce Seed Production

Abstract

Field cage experiments with the lygus bug, Lygus hesperus Knight, showed that these bugs probably cause no significant injury to lettuce seed plants. Under the conditions of these experiments one to four adult female lygus bugs per plant did not result in any significant decrease in lettuce seed yield or germination over that obtained in the checks, The lygus bugs did not cause any increase in the number of abnormal lettuce seedlings, and they did not cause any reduction in the weight or size of lettuce seeds. No nymphs developed in the lygus bug cages, although female bugs were used. It was determined that the bugs present in maturing lettuce seed fields were hyaline grass bugs, Liorhyssus hyalinus (Fab.). These bugs had been mistakenly called lygus bugs by seeds men in the Sacramento Valley. McKinney's experiments from 1939 through 1942 in Arizona revealed that the hyaline grass bug is a lettuce-seed-feeding insect. He reported that it took large numbers of the hyaline grass bug per plant (400 and more) to reduce lettuce seed yields seriously, and to eliminate viable seeds. McKinney's investigations indicated that 35 to 50 adult bugs per seed plant plus some nymphs were capable of instituting economic damage (especially to seed viability). The first lettuce seed to mature was not damaged by these bugs during an average season, but the later maturing seed was seriously damaged or destroyed.