Submitted to: Bulletin of Entomological Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2003
Publication Date: 8/15/2003
Citation: Agusti, N., Unruh, T.R., Welter, S.C. 2003. Detecting Cacopsylla pyricola (Hemiptera: Psyllidae) in predator guts using CO1 mitochondrial markers. Bulletin of Entomological Research. 93:179-185. Interpretive Summary: Insect predators are key agents in the control of insect pests in many crops. In pear they are especially important. Pear psylla, a key pest of pear, often requires over $400/acre to control each season, but studies show that much of this expense can be eliminated by fostering suitable predatory insects. Unfortunately, predation is notoriously difficult to study: insect predators leave no evidence that they have consumed a prey. Here we have developed a technique based on DNA amplification to identify predation events by predators of pear psylla. Using methods similar to that used in criminal forensics we can identify whether a specific predator has eaten a pear psylla within the last 32 hours. This approach will ultimately be used to provide quantitative estimates of predation occurring in orchards allowing more exact predictions of the action of predator populations on pest populations and further reductions in pesticide use.
Technical Abstract: Molecular markers were developed for the detection of the pear psylla Cacopsylla pyricola (Förster) (Homoptera: Psyllidae) in predator guts. Mitochondrial COI fragments were sequenced and twelve strand-specific primers were designed for the detection of this prey species. After testing several combinations, two pairs of primers, which amplified DNA fragments of 271bp and 188 bp were selected to study the detection period of the prey in the gut of Anthocoris tomentosus Pericart (Heteroptera: Anthocoridae). Predator adults were evaluated immediately after ingestion (t=0) and at 2, 4, 6, 8, 16, 24 and 32 h after feeding. Detection of C. pyricola DNA after 32 h digestion was observed with both pairs of primers. A higher percentage of the shorter 188bp sequence was amplified for all times tested suggesting a higher efficiency of detection with smaller fragments. The primers amplifying 188bp did so with the four psyllids tested whereas the primers designed to amplify a 271 bp fragment did so for only C. pyricola and its close relative, Cacopsylla pyri (L.). Both primers did not amplify DNA from representatives of the Coccinellidae, Chrysopidae, Hemorobiidae, Anthocoridae, Miridae, Salticidae, Aphidae, Tetranychidae and the Tortricidae, suggesting their suitability for general trophic studies.