Diuraphis noxia (Homoptera: Aphididae) population dynamics and impact of natural enemies in the Montpellier region of southern France

In a 2-yr field survey in the Montpellier region of southern France, mean density of Diuraphis noxia (Mordvilko) (Homoptera: Aphididae) varied greatly within and among fields and sample dates. Peak densities in the spring were from 70 +/- 17 to 532 +/- 143 aphids per square meter, which is 40-100 times lower than reported in the United States. Spatial variation in D. noxia density was strong at the scale of tillers and 1-m(2) quadrats. Predator density and parasitism varied greatly among fields and sample dates. At the scales of fields and 1-m(2) quadrats, predator density correlated positively with D. noxia density. When D. noxia population growth rate over each sample interval in each field was regressed stepwise on plant maturity, rainfall, temperature, and the densities of D. noxia, parasitoids, and predators, the only variable included in the regression model was predator density. D. noxia population growth rate declined with predator density, suggesting that predators limited D. noxia abundance.