Non-destructive detection of diapause in the western tarnished plant bug, Lygus hesperus Knight (Hemiptera: Miridae)

Authors: Spurgeon, Dale; Hull, Joe

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2018
Publication Date: 12/15/2018
Citation: Spurgeon, D.W., Hull, J.J. 2018. Non-destructive detection of diapause in the western tarnished plant bug, Lygus hesperus Knight (Hemiptera: Miridae). Journal of Cotton Science. 22:162-170.

Interpretive Summary: The Lygus bug complex (tarnished plant bug and western tarnished plant bug) currently represents the most important insect pest problem in U.S. cotton. The western tarnished plant bug overwinters in a non-reproductive state called adult diapause. However, the dynamics of this diapause and how it contributes to population survival are poorly understood. A more comprehensive understanding of Lygus overwintering might reveal opportunities to develop non-insecticidal management tactics to reduce the overwintering population. One factor limiting efforts to understand the dynamics of overwintering is lack of a non-destructive method to distinguish diapausing from non-diapausing adults. We evaluated a suite of characters for their ability to distinguish diapausing from non-diapausing Lygus bugs. Abdomen coloration of female Lygus was a reliable indicator of diapause state. During our studies, only a single female was incorrectly classified as diapausing by abdomen color. For male Lygus, abdomen length corrected for bug size (abdomen length / head width) was used to distinguish diapause with about 84% accuracy. Both characters provided improved accuracy compared with earlier reports. Application of these characters to individuals that were later starved allowed us to distinguish the survival patterns of diapausing and non-diapausing males and females. Although neither character (abdomen color for females, corrected abdomen length for males) was error-free, both offer sufficient accuracy to justify their use in studies of Lygus diapause. These characters provide the ability to non-destructively distinguish diapause in adult Lygus with reasonable accuracy, and should enhance efforts to better understand diapause and overwintering in this important pest species.

Technical Abstract: The western tarnished plant bug, Lygus hesperus Knight, overwinters in an adult diapause. However, the ecological implications of diapause to population survival are poorly understood. Enhanced understanding of L. hesperus overwintering ecology might reveal opportunities to develop ecologically-based management tactics. One factor limiting efforts to understand the dynamics of overwintering is lack of a non-destructive method to distinguish diapause. We evaluated a suite of external characters for utility in distinguishing diapausing from non-diapausing L. hesperus. Abdomen coloration of female L. hesperus was a highly-reliable indicator of diapause status. During our studies, a single female was misclassified using the abdomen color criterion. For male L. hesperus, corrected abdomen length (abdomen length / head capsule width) was used to predict diapause status with about 84% accuracy. Both criteria provided improved accuracy compared with earlier reports, in part because we limited their application to adults of a specific age (10 d) and reared at a specific temperature (26.7 degrees C). Application of these criteria to individuals that were subsequently starved allowed us to unambiguously distinguish the survival functions of diapausing and non-diapausing males and females. Although neither criterion (abdomen color for females, corrected abdomen length for males) was error-free, both offer sufficient accuracy to justify their use in studies of the ecology, physiology, or molecular biology of L. hesperus diapause. These criteria provide the ability to non-destructively distinguish the diapause status of adult L. hesperus with reasonable accuracy, and should enhance efforts to better understand diapause and overwintering ecology in this important pest species.