Predation and dislodgment of Schizaphis graminum (Homoptera: Aphididae), by adult Coccinella septempunctata (Coleoptera: Coccinellidae)
1990
McConnell, J.A. | Kring, T.J.
Adult Coccinella septempunctata L. were placed on grain sorghum plants, Sorghum bicolor (L.) Moench, at four growth stages with one of three greenbug, Schizaphis graminum (Rondani), densities under laboratory and field conditions. Greenbug predation and dislodgment rates for adults and nymphs were recorded during a 1-h observation period or until approximately 75% of the greenbugs were either consumed or dislodged. Greenbug nymphs were consumed at 4 and 1.3 times the rate of adults in laboratory and field tests, respectively. Adult greenbugs were 1.8 times and nymphs were 1.3 times more likely to be dislodged than consumed under laboratory conditions. In field tests, adults and nymphs were dislodged 5 and 4 times more often, respectively, than they were consumed. The number of greenbugs consumed/min in laboratory and field tests increased with plant stage and density with the exception of the bloom plant stage. The number of greenbugs dislodged for each consumed was directly related to prey density and plant stage. Evaluation of predator efficacy using only the number consumed may underestimate the effect of predation on greenbugs due to the dislodgment behavior. Dislodgment allows greenbugs to escape immediate predation, but may expose them to increased risk from other biotic and abiotic mortality factors.
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