Reproductive development of Lygus hesperus (Hemiptera: Miridae) adults under constant and variable temperatures

Authors: Brent, Colin; Spurgeon, Dale

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2019
Publication Date: 6/21/2019
Citation: Brent, C.S., Spurgeon, D.W. 2019. Reproductive development of Lygus hesperus (Hemiptera: Miridae) adults under constant and variable temperatures. Journal of Insect Science. 19(3):24;1-6.

Interpretive Summary: As water for agriculture becomes less available in the semi-arid western United States, alternative irrigation strategies may be necessary for continued cotton production. Alternative practices, like deficit irrigation, can result in episodic drought stress that raises daytime temperatures within the crop canopy. These higher temperatures may influence populations of important pests such as Lygus bugs. Field studies often associate lower population levels of Lygus bugs with limited irrigation. Recent studies of Lygus egg and nymphal development have demonstrated only subtle effects of the high, variable temperatures typical of moderate drought stress in cotton. When adult Lygus were exposed to low (15 degrees C), moderate (22 degrees C), and high (29 degrees C) constant and variable (+/- 8 degrees C) temperatures, their rates of reproductive development did not differ between constant and variable temperature regimes for the moderate or high temperatures. At the low temperature, the time to develop eggs, and development of the male sexual organs, was slightly shortened by the variable temperatures. These results suggest that temporary, episodic increases in crop canopy temperatures caused by moderate drought stress are unlikely to impact the growth of Lygus populations. Instead, a preference of immigrating adults for lush, well-watered cotton is a likely cause of the population responses previously observed in studies of the impacts of irrigation on Lygus bug populations.

Technical Abstract: As water for agriculture becomes less available in the semi-arid western United States, alternative irrigation strategies such as deficit irrigation may be necessary for continued crop production. Alternative irrigation practices in cotton (Gossypium spp. [Malvales: Valvaceae]) can result in episodic drought stress that alters temperature profiles within the crop canopy. These altered temperatures may influence populations of important pests such as Lygus hesperus Knight (Hemiptera: Miridae). Field studies often associate lower population levels of L. hesperus with limited irrigation. Recent studies of the thermal ecology of L. hesperus egg and nymphal development have demonstrated only subtle effects of the high, variable temperatures typical of moderate drought stress in cotton. However, influences of these conditions on L. hesperus adult reproductive development have not been studied. The reproductive development of L. hesperus adults was examined under constant (±0.2°C) and variable (±8°C) regimes at a low (15°C), moderate (22°C), and high (29°C) daily mean temperatures. No developmental differences were demonstrated between temperature regimes under moderate or high temperatures. At the low temperature, only the times to the occurrence of eggs, filled medial accessory glands, and filling seminal vesicles were shorter under variable regime, compared with the constant temperature. These results suggest that temporary, episodic increases in crop canopy temperatures caused by moderate drought stress are unlikely to impact L. hesperus population growth, and that host preference by the immigrating adults is a likely cause of the population responses observed in studies of the impacts of irrigation on L. hesperus populations.