Development and survival of Lygus hesperus (Hemiptera: Miridae) nymphs under constant and variable temperatures

Authors: Spurgeon, Dale; Brent, Colin

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2019
Publication Date: 2/11/2019
Publication URL: http://handle.nal.usda.gov/10113/6471071
Citation: Spurgeon, D.W., Brent, C.S. 2019. Development and survival of Lygus hesperus (Hemiptera: Miridae) nymphs under constant and variable temperatures. Journal of Insect Science. 19(1):1-6. https://doi.org/10.1093/jisesa/iez003.
DOI: https://doi.org/10.1093/jisesa/iez003

Interpretive Summary: Air temperatures of the arid western United States are often too high to favor development and survival of crop insect pests. However, the temperatures experienced by these pests within the crop canopy are usually lower than air temperatures. In cotton, improved irrigation practices that periodically stress the plants may impact pest and beneficial insects by increasing temperatures within the crop. Most information regarding the influences of temperature on development and survival of an important cotton pest, the western tarnished plant bug (Lygus), is derived from constant temperature studies. We examined the development and survival of immature Lygus (nymphs) under constant temperatures compared with temperatures that varied daily by +/- 18 degrees F, at daily average temperatures of 59, 72, and 84 degrees F. Under the lowest temperature, nymph development was faster when temperatures were variable compared with when they were constant. No differences in development times were observed between constant and variable temperatures at the medium temperature. Development under the high variable temperatures tended to be slower compared with the high constant temperature. Nymph survival was similar for constant and variable temperatures except at the lowest temperature, where survival was higher under the variable temperatures. Therefore, temporarily increased crop canopy temperatures caused by altered irrigation schemes are not likely to substantially affect the development of Lygus populations in cotton. However, enhanced development and survival of nymphs under low variable temperatures probably contribute to the survival of overwintering bugs when winter temperatures are low but above freezing.

Technical Abstract: Thermal environments of the arid western United States are often harsh compared with the ranges of temperatures favorable for development and survival of crop insect pests. In cotton (Gossypium spp., [Malvales: Malvaceae]), new irrigation practices such as deficit irrigation may impact populations of pest and beneficial arthropods by temporarily altering temperature profiles within the plant canopy. Most information regarding the temperature-dependent development and survival of an important cotton pest, the western tarnished plant bug (Lygus hesperus Knight [Hemiptera: Miridae]), is derived from constant temperature studies. We examined the development and survival of L. hesperus nymphs under constant (+/- 0.2 degrees C) and variable (+/- 8 degrees C) temperature regimes at daily mean temperatures of 15, 22, and 29 degrees C. Under the low temperature (15 degrees C), stadium lengths and duration of the entire nymphal stage were shorter when temperatures were variable compared with a constant temperature. No differences in development times were observed between regimes at the medium temperature (22 degrees C). Except for the 1st stadium, development times under the high variable temperature regime were longer compared with the high constant regime (29 degrees C). Nymph survival was unaffected by temperature regime except at the lowest temperature, where daily thermal fluctuations substantially improved survival compared with the constant conditions. These results suggest that temporarily increased crop canopy temperatures caused by altered irrigation schemes are unlikely to substantially reduce the growth of L. hesperus populations. However, enhanced nymphal development and survival under low variable temperatures likely contribute to the survival of overwintering L. hesperus in the absence of acute, low-temperature mortality.