2012 Annual Report
1a.Objectives (from AD-416):
To quantify Lygus and their natural enemy dipersal patterns between trap crops (strategically placed alfalfa weeds) and an organically grown strawberry cropping system. This research will lead to more efficient(less costly and less environmental impact)pest management of Lygus in strawberry.
1b.Approach (from AD-416):
Will assist with marking the trap crops and strawberry fields with various markers and assaying all the captured insects for the presence of the markers using a suite of enzyme-linked immunosorbent assays. These data will quantify Lygus movement between the various cropping systems. Documents Reimbursable with UC Santa Cruz. Log 39451. Formerly 5347-22620-017-13R (12/10).
This is the final report for project 5347-22620-021-05R, which was extended to facilitate completion of a study of dispersal of Lygus and associated natural enemies from non-crop weedy habitats. 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. Alfalfa is highly attractive to lygus bugs and is used as a trap crop in California organic strawberries. A multi-year study was completed that determined the abundance and distribution of lygus between two alfalfa trap crops separated by 50 strawberry rows. The movement of lygus from an alfalfa trap crop into adjacent strawberry rows or trap crops was studied using chicken egg albumin and bovine milk markers in a protein mark-capture technique. The study revealed that the vast majority of marked lygus remained in alfalfa trap crops, rather than dispersing out into strawberry rows. Strips of alfalfa planted intermittently within organic strawberry fields served as a trap crop for Lygus and a refuge for their predators and parasitoids. Also, a small percentage of marked lygus were captured in neighboring alfalfa trap crops, located 62 m from the point of protein application. This study verifies that the attenuation of lygus bug movement by alfalfa in organic strawberries is a key component of successful trap cropping. A second component of the project examined the movement of Lygus and associated predators and parasitoids into strawberries from non-crop weedy areas typical of Lygus overwintering habitat. Results indicated the majority of lygus originating from non-crop weedy areas dispersed to the alfalfa trap crop rather than to strawberries. This information will be used by organic strawberry producers to optimize non-pesticide based control tactics including the use of alfalfa trap crops.