Implications of Russian wheat aphid, Diuraphis noxia, falling rates for biological control in resistant and susceptible winter wheat

摘要

The restriction of aphid reestablishment onto plants by epigeal predators represents a critical component of integrated pest management. To further realize the potential that these predators might have in control programs, it is necessary to quantify such behavior as aphid falling rate to reveal the number of aphids that are available as potential prey. This study calculated the falling rate of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Sternorrhyncha: Aphididae), and tested whether this aphid more likely fell from wheat plants that differed between flat leaf architecture versus those with furled leaves. Specifically, the hypothesis was tested that a resistant wheat line (flat leaves) will have a higher aphid falling rate than a susceptible closely related line (furled leaves). The experiment was performed at Fort Collins and Akron, Colorado, USA, from May through July, 2008. Aphids were sampled from infested wheat rows to estimate aphid density, and sticky traps were used to capture falling aphids and to measure falling rate. Falling rates ranged from 0.7 to 69.5% in Fort Collins and from 1.4 to 59.5% in Akron. The falling rate of D. noxia was more influenced by plant growth stage than aphid densities, with the highest falling rate occurring after wheat senescence. Wheat plants with flat leaf architecture did not significantly increase aphid falling rate. Diuraphis noxia falls at a higher rate at lower aphid densities, which is when epigeal predators could have their greatest biological control impact.