UC Davis Agricultural and Resource Economics

Brittney Goodrich, University of California, Davis

Citrus Greening Disease and Pesticide Usage in California

Date and Location

Thursday, November 9, 2023, 4:10 PM - 5:30 PM
ARE Conference Room, 2102 Social Sciences and Humanities


Huanglangbing (HLB), also referred to as citrus greening disease, has had an unprecedented effect on the U.S. citrus industry. This bacterial disease which has no known cure gained a foothold in the state of Florida in 2005, which has since seen citrus yields and acreage decrease by 87% and 51%, respectively. HLB is spread by the Asian Citrus Psyllid (ACP) insect. Due to mobility of the ACP, studies have shown that area-wide pest management (AWPM) is most effective for slowing the spread of HLB, yet AWPM has not been widely implemented in Florida (Singerman and Useche, 2019). California is now the largest producer of citrus in the U.S., producing $3.1 billion worth of citrus in 2021 and is at risk of a similar outcome to Florida’s industry. ACP was first detected in San Diego County, California in 2008, and has since been detected throughout the citrus growing regions of California. Citrus greening disease was first detected in California in 2012, but detections have yet to transition from residential settings into commercial citrus orchards. Growers attempt to control ACP populations and prevent possible HLB infection in their orchards with pesticides.

In this study, we use California’s Pesticide Use Reporting (PUR) Database and a database of ACP detections collected by the California Department of Food and Agriculture (CDFA) to analyze how the introduction of ACP and HLB have impacted economic outcomes of citrus growers in California through additional pesticide costs. We use a Differences-in-Differences framework outlined by Callaway and Sant’Anna (2021) to estimate the effect of a nearby ACP detection on growers’ pesticide applications. We differentiate between individual effects of an ACP detection within a 1 mile x 1 mile section and neighboring effects of an ACP detection in a neighboring section to determine whether there is evidence of widespread use of AWPM. We find that on average, pesticide applications increased by 0.5 applications per acre per year when an ACP was detected within a section or in a neighboring section. This effect is much larger when only considering sections where an ACP was detected, in which the increase was 1.4 applications per acre per year. There was no statistically significant average effect of an ACP detection in a neighboring section, suggesting AWPM was not commonly implemented over the 2008-2018 time period. However, there was heterogeneity in the neighboring effect across years. In years 2012, 2013, and 2014 there is evidence that growers in sections neighboring an ACP detection also displayed higher pesticide applications. Given the first HLB detection in California occurred in 2012, this suggests AWPM may have been used more widely once the risk of HLB infection increased.

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