Variety mixtures of wheat influence aphid populations and attract an aphid predator

Abstract

In crop fields, increasing plant species diversity can help manage insect pests, but using plant intraspecific diversity has received less attention as an insect pest management strategy. To explore the potential of crop genotypic diversity for managing insect pests, we used a wheat-aphid-lady beetle model system. We performed greenhouse and laboratory experiments comparing six monocultures and four-variety mixtures. We found that genotypic diversity did not strongly influence aphid populations at the stand level, but did stabilize populations. At the individual plant level, populations on certain varieties differed in mixtures from what would be expected based on populations on the variety in monocultures, including one that consistently hosted lower aphid populations when it was grown in mixtures. When we then tested five of the most promising mixtures, we found none decreased aphid populations compared to monocultures. Diversity of the surrounding neighborhood significantly influenced aphid populations on individual plants of certain varieties. Wheat mixtures did not overyield relative to monocultures, as other studies have found, but all measures of productivity were stabilized by mixtures. In behavioral experiments, aphids did not prefer mixtures or monocultures, but lady beetles were significantly attracted to mixtures. In the field, bottom-up effects on aphids and effects on natural enemies could create pest-management benefits. Based on the work we present here, increasing diversity per se may not improve aphid management aside from stabilizing populations; rather, specific types of mixtures that include influential varieties appear to be crucial for fostering beneficial interactions that can benefit insect pest management.