UC Davis Agricultural and Resource Economics

Yanan Zheng, University of California, Davis

Cross-crop Spatial Externalities of Pesticide Use: Management of Lygus Bugs in the San Joaquin Valley, California

Date and Location

Thursday, April 21, 2022, 4:10 PM - 5:30 PM


Lygus bug is a key pest of California cotton. It is a highly mobile insect that typically develops populations on other hosts, most notably alfalfa and safflower, in early April to late July and migrates into cotton when those crops are harvested. One of the strategies to control lygus in cotton is to apply pesticides to alfalfa and safflower in the early season to reduce lygus migrations into cotton. Lygus is not an economic pest for those two host crops, however some pesticides applied to those crops to manage target pests provide incidental control of lygus as well. Alfalfa and safflower growers who apply such pesticides create positive externalities for cotton growers. Using field-level data on pesticides applied to control lygus in alfalfa, safflower, and cotton in the San Joaquin Valley from 2010 to 2019, this study explicitly considers the timing of pesticide applications and examines whether: 1) early pesticide applications to alfalfa and safflower generate positive externalities for cotton production; and 2) cotton growers capture cross-crop benefits by growing alfalfa and/or safflower and applying pesticides to these crops in the early season. The answer to both question is yes. To establish the role of application timing, we conduct another set of analyses ignoring the timing of pesticide applications. Our results show that ignoring the timing of applications can lead to an underestimate of the magnitude of cross-crop benefits from pesticide use and fail to find positive externalities.

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