|TUELHER, EDMAR - Universidade Federal De Vicosa|
|OLIVEIRA, EUGENIO - Universidade Federal De Vicosa|
Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2019
Publication Date: 2/6/2020
Citation: Tuelher, E.S., Backus, E.A., Cervantes, F.A., Oliveira, E. 2020. Quantifying Lygus lineolaris stylet probing behavior and associated damage to cotton leaf terminals. Journal of Pest Science. 93:663-677. https://doi.org/10.1007/s10340-019-01184-8.
Interpretive Summary: The tarnished plant bug, Lygus lineolaris, is an important native pest of cotton in the mid-southern United States. L. lineolaris feeds on more than 300 plant species, especially preferring flower buds over leaves. Feeding by probing piercing-sucking mouth parts (stylets) into buds can result in bud abscission, deformed fruits, site necrosis, and reduced plant growth. However, L. lineolaris also are reported to feed on leaves, especially at the tips of stems, causing stem tip abortion and deformed leaves, reduced plant growth, and excessive branching. There is little known about exactly what feeding behaviors trigger injury symptoms on cotton leaves. The most accurate way to study the feeding behavior of piercing-sucking insects is electropenetrography (EPG). EPG was used to study L. lineolaris stylet probing behavior for 3rd, 4th, and 5th instar immatures plus male adults on young leaves at the tips of cotton stems. EPG waveforms were measured for non-probing and probing behaviors (plant cell rupturing, transition tasting/testing behavior, and ingestion [swallowing]). Insect foliar damage was photographed at regular intervals up to seven days after insect feeding, and damage areas were digitally measured. The longest duration of probing behavior was for cell rupturing, especially for 4th and 5th instars followed by 3rd instars and adults. The greatest damage to cotton leaves occurred when high numbers of wound-inducing cell-rupturing probes, which inject enzymatically active saliva, were combined with minimal ingestion of saliva. On cotton leaves, this style of feeding matches that of 4th and 5th instar nymphs. These results explain why older nymphs are the most damaging life stages of L. lineolaris in the field, and help to better target application of insecticides or transgenic cotton plants to reduce crop loss.
Technical Abstract: Lygus lineolaris (Palisot de Beauvois) is an important native pest of cotton in the mid-southern United States 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 leaf terminals. There is little known about feeding behaviors performed on cotton leaves nor how injury symptoms are triggered. The most accurate way to study the feeding of piercing-sucking insects is electropenetrography (EPG). EPG was used to quantify L. lineolaris stylet probing behaviors on cotton leaf terminals for 3rd, 4th, and 5th instars plus male adults. Both non-probing and 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 4th and 5th instars followed by the remaining immature insects. 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 feeding matches that of older nymphs. Thus, even small amounts of cell rupture feeding and ingestion by older L. lineolaris nymphs is 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.