Submitted to: International Organization for Biological Control of Noxious Animals and Plants(IOBC) Nearctic Regional Section (NRS) Newsletter
Publication Type: Popular Publication
Publication Acceptance Date: July 19, 2009
Publication Date: July 22, 2009
Citation: Weber, D.C. 2009. Dark side of predation: Blind side in biocontrol research. International Organization for Biological Control of Noxious Animals and Plants(IOBC) Nearctic Regional Section (NRS) Newsletter. 31(2):2
Predation of pests by arthopod predators (insects and spiders) occurs around the clock. Yet little effort has been made to characterize the 24-hour pattern of predation on insect pests in the field, particularly events that occur nocturnally. The few round-the-clock observations in various ecosystems have shown that predator communities differ greatly around the diel cycle. This means that daytime appraisals, which are the norm, are at best biased. And worse, predators causing significant mortality to target pests may be completely overlooked. Depending on the system, cursorial (running) spiders, carabid and other predatory beetles, cockroaches, ants, and earwigs, are disproportionately important after dark. To address this, in recent experiments in Maryland, we have observed egg masses of Colorado potato beetle (CPB) in potato crops, and monitored them every three hours day and night to determine predator occurrence and egg consumption. The natural enemy complex is dominated by beetles and true bugs. The majority of predation events occurred after dark, and the fewest during the afternoon. The diel pattern of occurrence of predators on sentinel egg masses was mostly unique for different predator species. Also important, Chauliognathus sp. had not previously been recorded as a predator of CPB, probably because it was active only at night. Our results in potato are consistent with those of Pfannenstiel and coworkers in field crops, in that nocturnal predation was at least equal to diurnal predation, and often involved predators that foraged primarily at night. Remedying the serious nocturnal deficiency in agroecology will take much more observational effort, but will yield vital insights into important pest control services provided by predators, which will be useful to researchers, pest managers, and growers.