Author
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Ugine, Todd |
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Submitted to: Biological Control
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/15/2011 Publication Date: 12/1/2011 Citation: Ugine, T.A. 2011. The effect of temperature and exposure to Beauveria bassiana on tarnished plant bugs Lygus lineolaris (Heteroptera: Miridae) population dynamics and the broader implications of treating insects with entomopathogenic fungi. Biological Control. 59(3):373-383. Interpretive Summary: Tarnished plant bugs, Lygus lineolaris, are a particularly damaging insect pest of cotton and many seed and forage crops. They also are able to readily develop resistance to synthetic chemical pesticides. Studies were conducted to determine exactly how temperature and infection with the fungal pathogen Beauveria bassiana affect plant bug reproduction. The information from these studies will inform researchers as to what time of year might be the best time to target plant bug populations by determining at what temperature infection has the largest impact on population growth. It was determined that treatment of plant bugs that had finished their preoviposition period at any temperature had little effect on the growth rate of the population. However, the time to death from infection was shorter than the preoviposition period at all of the temperatures tested, suggesting the need to treat non-reproductive/diapausing populations or populations that are still in their preoviposition period as occurs in the winter and early spring months. Technical Abstract: Tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois) (Heteroptera, Miridae) are a major pest of cotton in most of the cotton growing regions of the Southern US. Studies were conducted to investigate how temperature and Beauveria bassiana (Balsamo) Vuilllemin infection impacted L. lineolaris fecundity and longevity, with the goal of determining what temperatures optimized B. bassiana’s control potential. Adult female tarnished plant bugs were treated with B. bassiana and maintained at constant 18, 21, 25, 30 or 32 ºC. The number of eggs laid was determined daily until death. Treatment with B. bassiana caused large reductions in the total number of eggs laid (45-76%) at all temperatures, however there was no effect of infection on the daily rate of egg production. There was not a sublethal effect of infection on egg production on the last full day of life. The intrinsic rates of natural increase, and the associated population doubling times were not largely impacted by treatment with B. bassiana; doubling times increased with treatment an average of 3.5 days (range 0.5-7.7 days). There was a temperature dependent trend in the length of the preoviposition period and the days to death after treatment with B. bassiana. As temperature increased from 18-32 ºC, the number of days to death converged on the preoviposition period. The maximum difference was observed at 18 ºC (5.3 days different) compared to 30 ºC and 32 ºC (0.3 days). These results strongly suggested that treatment of tarnished plant bugs with B. bassiana should be performed when plant bugs are in diapause or when temperatures are cool in order to take advantage of the slow acting nature of infection. |
