2013 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 inhouse 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 against the lygus bug. 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 analyzed for lygus-specific DNA. This method determines which species of predators are preying on lygus (e.g., there will be lygus DNA in their gut). To date, we have collected and analyzed the gut contents of over 1,200 predator specimens. Data indicate that spiders, damsel bugs, and lacewing are actively preying on lygus. At present, we are collecting predators from the field to obtain a second year of data. 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 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. Currently we are conducting a second year of field research to obtain more data. 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.