Submitted to: Arthropod-Plant Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/20/2008
Publication Date: 12/14/2008
Citation: Lundgren, J.G., Hesler, L.S., Tilmon, K.J., Dashiell, K.E., Scott, R.A. 2009. Direct effects of soybean varietal selection and Aphis glycines-resistant soybeans on natural enemies. Arthropod-Plant Interactions. 3:9-16. DOI 10.1007/s11829-008-9053-4. Interpretive Summary: Two important pest management tactics that are often used in conjunction are host plant resistance and biological control. Many predators rely on plants as sources of food and shelter, and this reliance becomes particularly important when crop plants express traits that are intended to resist insect pests. Soybean aphid, an invasive pest from Asia, is a recent target of host-plant resistance programs, and here we test how resistant soybeans from different genetic backgrounds affect two key aphid predators, the multi-colored asian ladybeetle (Harmonia axyridis) and the insidious flower bug (Orius insidiosus). We found that aphid resistant soybeans adversely affected adult performance in ladybeetles, and that soybean varietal selection affected bug longevity, even when suitable prey was abundant. Perhaps as importantly, both predators had low survival and fitness when reared on soybeans versus on a common agronomic weed, ivyleaf morning glory. Our data support the conclusions that the direct effects of soybean varietal selection should be considered when designing IPM programs involving biological control, and that including non-soybean plants within soybean fields could facilitate establishment and improve the fitness of key aphid natural enemies.
Technical Abstract: The direct effects of three soybean base genetics, each represented by an Aphis glycines-resistant and susceptible variety, on the fitness and performance of two key predators (Orius insidiosus and Harmonia axyridis) were evaluated in the laboratory. Predators were reared from hatch through adulthood in Petri dishes with cut trifoliolate leaves of the designated soybean variety, using eggs of Ephestia khueniella as surrogate prey to eliminate prey-mediated effects of the host plant. Preimaginal survival and development, sex ratio, adult longevity, fecundity, and size were compared among treatments and a no-plant control. An additional experiment compared life-history parameters of predators caged with soybean versus Ipomoea hederacea (ivyleaf morning glory). Aphid resistance reduced the adult longevity of H. axyridis, but O. insidiosus was unaffected by resistance traits. However, adult O. insidiosus lived longer on soybeans with Group C base genetics than the other soybean varieties. Other parameters were not affected by soybean base genetics or resistance, but both predators generally performed worse on soybean than on I. hederacea or no-plant controls. The results suggest that soybean varietal selection, particularly with respect to A. glycines-resistance, may directly affect biological control agents. Also, implications of the generally poor suitability of soybean for natural enemies are discussed within the context of current crop production practices.