Relative dispersal ability of a key agricultural pest and its predators in an annual agroecosystem

Authors: SIVAKOFF, FRANCES - University Of California; ROSENHEIM, JAY - University Of California; Hagler, James

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2012
Publication Date: 9/23/2012
Citation: Sivakoff, F.S., Rosenheim, J.A., Hagler, J.R. (2012). Relative dispersal ability of a key agricultural pest and its predators in an annual agroecosystem. Biological Control. 63:296-303

Interpretive Summary: In agroecosystems staggered planting dates, pesticide treatments, and harvesting events create a “shifting mosaic” of habitats that leads to frequent recolonization by insect pests and their natural predators and parasitoids. In these systems, an untested assumption is that herbivore pests have higher rates of dispersal relative to their natural enemies and are thereby thought to escape from biological control. In California, lygus bugs are under poor biological control despite having a diverse suite of known predators. One possible explanation is that lygus has greater dispersal ability relative to its predators. We performed a large-scale insect dispersal study by marking an alfalfa field containing lygus and its predators directly in the field with an aerial application of a protein marker. Following marking, the alfalfa field was harvested by the grower, prompting an insect dispersal event out of the alfalfa field. At several times following harvest, surrounding cotton fields were sampled at known distances from the marked field to quantify movement by lygus and its predators. Contrary to the general view, our data do not suggest that lygus routinely out-disperses its predators. Instead, the dispersal ability of lygus fell near the average dispersal ability of its predators.

Technical Abstract: In annual agroecosystems staggered planting dates, pesticide treatments, and harvesting events create a “shifting mosaic” of habitats that leads to frequent recolonization by herbivores and natural enemies. In these systems, an untested assumption is that herbivores have higher rates of dispersal relative to their natural enemies and are thereby thought to escape from biological control by colonizing habitats before their predators. In California’s San Joaquin Valley, the generalist pests Lygus spp. are under poor biological control despite having a diverse suite of known predators. One possible explanation is that Lygus has greater dispersal ability relative to its predators. To examine this directly, we performed a large-scale mark-capture study by marking an alfalfa field containing Lygus and its predators with an aerial application of a protein marker. Following marking, the alfalfa field was harvested by the grower, prompting a dispersal event. At several times following harvest, surrounding cotton fields were sampled at known distances from the marked field to quantify movement by Lygus and its predators. Contrary to the general view, our data do not suggest that Lygus routinely out-disperses its suite of predators. Instead, the dispersal ability of Lygus fell near the average dispersal ability of its predators.