USING GIS APPROACHES TO STUDY WESTERN TARNISHEDPLANT BUG IN THE SAN JOAQUIN VALLEY OF CA

摘要

The western tarnished plant bug (Lygus hesperus) is a key pest in many crops in the San Joaquin Valley (SJV) includingcotton, dry beans, seed alfalfa, and various fruits and vegetables. Populations of this indigenous insect begin at very lowdensities in spring but build through the summer on a variety of host plants. As one plant or crop becomes unsuitable theinsect moves into neighboring crops. Geographic Information Systems (GIS) provides an ideal tool to study the concentrationand movement of lygus through the season. GIS techniques were used to characterize various landscapes in the study areathat provide lygus habitat. Several townships were analyzed throughout the valley in general to identify differences incropping patterns, and specifically to investigate the pattern of cotton and alfalfa adjacency. In addition, Landsat imagery wasprocessed to identify areas of senescing natural vegetation that are in close proximity to cultivated areas. Finally, actual lyguspopulation dynamics in bordering farm areas were mapped using real-time field data. These approaches provide a powerfultool to understand the landscape in lygus population development and movement. The concept of crops and plants acting assources out of which lygus move or sinks into which lygus move can be studied on a regional scale. The role of individualcrops such as alfalfa hay on the intensity of lygus in an area might be used in a predictive manner to prescribe regionalmanagement of this pest. GIS also provides useful tools to help cotton growers and consultants visualize complex cropinteractions and lygus movement.