Impact of Lygus hesperus (Hemiptera: Miridae) Feeding and Oviposition on Lettuce

Abstract

The western tarnished plant bug, Lygus hesperus Knight (Hemiptera: Miridae), is an important insect pest of lettuce, Lactuca sativa L. in the central coast region of California. However, little is documented on the injury symptoms relative to levels of L. hesperus infestation on lettuce. Experiments were conducted in which lettuce plants were exposed to 0, 1, 3, 5, and 10 L. hesperus adults for 2 and 7 days. The major injury symptom observed was lesions on the midrib of the leaves, and under low to moderate infestation (e.g., one to five adults per plant) after 2 days of exposure these lesions were not significantly different from the insect-free control. Under heavy infestation (e.g., 10 adults per plant), however, lesions developed rather quickly after 2 days of exposure. The number of lesions was positively associated with numbers of feeding sites and eggs. When heavy infestation lasted for a week, most of the plants died. At low to moderate infestation, more lesions developed compared with the insect-free control. After a weeklong exposure, an increase in number of lesions was negatively associated with plant height. The results emphasize the need for regular scouting to facilitate immediate management decisions and actions to reduce losses from L. hesperus feeding and oviposition injury in lettuce.