Researchers report the effects of land use, transgenic cotton, and weather on cotton pests in China. China is one of the world's largest pesticide consumers, with cotton being the most heavily treated agricultural crop. To assess the influence of landscape complexity, pest-control technology, and weather on long-term cotton pest severity and management, Wei Zhang and colleagues analyzed longitudinal data for 51 Chinese counties from 1991 to 2015 on three major cotton pests: cotton aphid, mirid bug, and cotton bollworm. Both cotton bollworm severity and the amount of insecticide used to control bollworm declined during the study period, while the share of Bacillus thuringiensis cotton, which is genetically resistant to bollworm, increased. Reduced insecticide use against bollworm was associated with a reduction in aphid severity but an increase in mirid bug severity. Mirid bug severity also increased with increasing May temperatures. Each pest responded differently to changes in land use, and farmers routinely sprayed against aphid and bollworm even at nondamaging infestation levels. The results suggest that reduced spraying against bollworm affected the entire pest complex, helping to suppress aphids by increasing natural aphid predators but also reducing mirid bug suppression. The findings highlight the potential unintended consequences of pest-management practices and suggest that projected climate warming could increase the risk of pest outbreaks, according to the authors.
###
Article #17-21436: "Multidecadal, county-level analysis of the effects of land use, Bt cotton, and weather on cotton pests in China," by Wei Zhang et al.
MEDIA CONTACT: Wei Zhang, International Food Policy Research Institute, Washington, DC; tel: 202-862-5626; e-mail: < w.zhang@cgiar.org >; Yanhui Lu, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, CHINA; tel: + 861062816631; e-mail: < yhlu@ippcaas.cn >
Proceedings of the National Academy of Sciences