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Project description

Developing and comparing regional management strategies for western tarnished plant bug (Lygus hesperus) in the San Joaquin Valley. (01FE019)
Program UC IPM competitive research grants program
Principal
investigator 		P.B. Goodell, UC IPM, Kearney Agricultural Center
Host/habitat Cotton; Beans; Alfalfa
Pest Western Tarnished Plant Bug Lygus hesperus
Discipline Entomology
Review
panel 		Field Ecology
 Start year (duration)  2001 (One Year)
Objectives Develop crop maps in four locations in the San Joaquin Valley (SJV) to inventory suitable hosts for Western Tarnished Plant Bug (WTPB) and to follow cropping changes through the growing season.

Analyze crop maps for spatial relationships among crops in an area and compare and contrast the four different cropping ecosystems in the SJV.

Follow WTPB population development in selected crops within a mapped area in order to relate WTPB population dynamics with landscape changes.

Develop a community-based structure through which cropping and WTPB information can be collected and management strategies delivered.

Final report Lygus bugs (Lygus hesperus) are important insect pests on many crops including cotton, beans, lettuce, seed alfalfa, strawberries, and tree fruit. Their population density begins low in the spring and increases during the summer. Many crops and weeds can act as hosts during this population buildup. As one crop is prepared for harvest or a weed begins dries out, lygus are forced to move into neighboring crops. As crops are harvested through the years, lygus are forced to concentrate in the remaining fields, such as cotton or fall lettuce.

Alfalfa hay may play a key role in providing a stable habitat for lygus. This preferred host is not affected by the presence of lygus and, with the exception of harvest, the crop is maintained in a vigorous vegetative state. We compared the cropping mosaic in two distinctly different areas containing about 36 sq. miles. One area was near Buttonwillow, Kern Co. and the other near Five Points, Fresno Co. The Kern site had a 2: 1 cotton alfalfa ratio while the Fresno site had no alfalfa.

Lygus populations in cotton were followed at Buttonwillow site and mapped by field over time. Relationships between cotton and alfalfa are being evaluated including proximity and influence of hay harvest on movement into cotton.

Comparing Kern and Fresno sites may offer insight into the importance of alfalfa as lygus refugia across a wide area. At a regional level, these sites offer opportunities to study the abundance and placement of alfalfa hay and its influence of lygus movement. However, technical developments in providing GIS-based support via the Internet will play an important role in the adoption and utilization of this technology.

First-year
progress 		Lygus bugs (Lygus hesperus) are important insect pests on many crops including cotton, beans, lettuce, seed alfalfa, strawberries, and tree fruit. Their population density begins low in the spring and increases during the summer. Many crops and weeds can act as hosts during this population buildup. As one crop is prepared for harvest or a weed dries out, lygus are forced to move into neighboring crops. As crops are harvested through the years, lygus are forced to concentrate in the remaining fields, such as cotton or fall lettuce.

Alfalfa hay may play a key role in providing a stable habitat for lygus. This preferred host is not affected by the presence of lygus and, with the exception of harvest, the crop is maintained in a vigorous vegetative state. We compared the cropping mosaic in two distinctly different areas containing about 36 square miles. One area was near Buttonwillow, Kern Co and the other near Five Points, Fresno Co. The Kern site had a 2:1 cotton to alfalfa ratio while the Fresno site had no alfalfa.

Lygus populations in cotton were followed at Buttonwillow site and mapped by field over time. Relationships between cotton and alfalfa are being evaluated including proximity and influence of hay harvest on movement into cotton.

Comparing Kern and Fresno sites may offer insight into the importance of alfalfa as lygus refugia across a wide area. At a regional level, these sites offer opportunities to study the abundance and placement of alfalfa hay and its influence of lygus movement.

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