Effects of Local and Landscape Factors on Population Dynamics of a Cotton Pest

Abstract

<div><h3>Background</h3><p>Many polyphagous pests sequentially use crops and uncultivated habitats in landscapes dominated by annual crops. As these habitats may contribute in increasing or decreasing pest density in fields of a specific crop, understanding the scale and temporal variability of source and sink effects is critical for managing landscapes to enhance pest control.</p> <h3>Methodology/Principal Findings</h3><p>We evaluated how local and landscape characteristics affect population density of the western tarnished plant bug, <em>Lygus hesperus</em> (Knight), in cotton fields of the San Joaquin Valley in California. During two periods covering the main window of cotton vulnerability to <em>Lygus</em> attack over three years, we examined the associations between abundance of six common <em>Lygus</em> crops, uncultivated habitats and <em>Lygus</em> population density in these cotton fields. We also investigated impacts of insecticide applications in cotton fields and cotton flowering date. Consistent associations observed across periods and years involved abundances of cotton and uncultivated habitats that were negatively associated with <em>Lygus</em> density, and abundance of seed alfalfa and cotton flowering date that were positively associated with <em>Lygus</em> density. Safflower and forage alfalfa had variable effects, possibly reflecting among-year variation in crop management practices, and tomato, sugar beet and insecticide applications were rarely associated with <em>Lygus</em> density. Using data from the first two years, a multiple regression model including the four consistent factors successfully predicted <em>Lygus</em> density across cotton fields in the last year of the study.</p> <h3>Conclusions/Significance</h3><p>Our results show that the approach developed here is appropriate to characterize and test the source and sink effects of various habitats on pest dynamics and improve the design of landscape-level pest management strategies.</p> </div