Use of a New Immunomarking Method to Assess Movement by Generalist Predators Between a Cover Crop and Tree Canopy in a Pear Orchard

摘要

Poor understanding of natural enemy movement between cover crop and crop habitats has limited effective use of cover crops to enhance biological control of pest arthropods in agricultural systems. To address this problem, we used an egg-albumin immunomarker sprayed on a legume cover crop to monitor movement by generalist predators from the cover crop into the canopy of pear trees in a Central Washington State pear orchard. Generalist predators in four taxa (Heteroptera, Coccinellidae, Chrysopidae, Araneae) were collected from both cover crop and pear tree canopy, and tested using enzyme-linked immunonoassay (ELISA) methods to determine if the marker was present. In the three years of study, > 90% of arthropods collected from the cover crop had acquired the marker, indicating that we had excellent coverage and marking of arthropods with the solution. Between 17 and 29% (depending upon the year of study) of the approximately 2000 specimens collected from the tree canopy were also found to be marked,which is evidence that a percentage of the generalist predator community in the tree canopy had originated from or had visited the legume cover crop. These specimens included spiders and immature insects, which presumably colonized the tree either by walking up the tree trunk or (for spiders) by ballooning into the canopy. Some care must be taken in applying this technology or in interpreting results, due to unknown effects of the marker on arthropod behavior, and to questions of whether the marker might transfer from marked to unmarked insects as they interact in the field. Despite these caveats, the technology described here provides a new tool for assessing the effects of habitat management on movement of generalist predators in crop systems.