Quantifying Lygus lineolaris stylet probing behavior and associated damage to cotton leaf terminals.
Lygus lineolaris is an important native pest of cotton in the mid-southern USA and a potential invasive species in other parts of the world. L. lineolaris feeds on more than 300 plant species, especially preferring reproductive plant organs but also feeding on young terminal leaves. There is little known about feeding behaviors performed on cotton leaves nor of associated injury symptoms triggered. Herein, we used the most accurate way to study feeding of piercing-sucking insects, i.e., electropenetrography (EPG). EPG was used to quantify L. lineolaris feeding behaviors on young terminal leaves of cotton, for third, fourth, and fifth instars plus male adults. Both non-probing (combined walking, standing and antennation) as well as probing behaviors (cell rupturing, transition, and ingestion) were compared with a time course of digitally measured leaf damage. Overall, L. lineolaris, especially adults, spent most time in non-probing behaviors. For probing behaviors, the longest duration was cell rupturing, especially for fourth and fifth instars followed by the third instars. The greatest damage to cotton leaves occurred when high numbers of wound-inducing cell-rupturing probes, which inject macerating saliva, were combined with minimal subsequent ingestion of saliva. On cotton leaves, this style of cell rupturing matches that of older nymphs. Thus, even small amounts of cell rupture feeding and ingestion by older L. lineolaris nymphs are damaging to cotton leaf terminals. These results help to understand the cause of damage to L. lineolaris hosts and consequently aid in developing strategies to reduce crop loss.