2012 Annual Report
1a.Objectives (from AD-416):
Study various aspects of arthropod predation on the key pest (Lygus) of organically managed strawberries in CA.
1b.Approach (from AD-416):
We will study arthropod population dynamics and identify key predators of Lygus hesperus in organically managed strawberry fields and nearby alfalfa trap crops.
This Reimbursable Agreement is in support of Objective 2 – Characterize and exploit interactions among plants, insect pests and natural enemies; investigate the role of arthropod predators and trophic interactions for improved biological control, of the approved parent project. The western tarnished plant bug (lygus bug) is a key pest of organic strawberries in California. Unfortunately, insecticides that comply with regulations for organic strawberry production are expensive and have low efficacy. Thus, organic growers seek a biologically-based approach for lygus bug management. This approach necessitates an improved understanding of the activities and effectiveness of key predators of lygus bugs in organic strawberries. Two methods we developed are being used to provide different, but complementary information about the beneficial insects preying on lygus bugs. In the first method the contents of the digestive tracts of field-collected predators are chemically analyzed for DNA specific to lygus bugs. This method is being used to determine which species of predators are preying on lygus. To date we have collected the predator specimens from field plots, but the DNA assays have not been completed. In the second method, individual lygus bugs were marked with specific protein markers. The marked lygus were released into field cages containing native predators. These predators were later collected and their digestive tracts were chemically analyzed for presence of the protein markers. This method precisely identifies individual predators that have fed on lygus. The gut assays revealed that spiders and earwigs were actively feeding on the protein-marked lygus. The research outcomes of this project will provide information regarding how predators function in organic strawberries, including which predators are most important to recognize during field scouting assessments, and how alfalfa trap crops can be spatially arranged to enhance predator effectiveness.