Organic farming can produce an increase in species richness and in the abundance of predatory insects and weeds. But does a rise in biodiversity have an impact on pest control? Biology majors Cody Nagy and Mark Gapinski studied the impact of organic agricultural practices on insect pest control as part of their Summer Fellows research in Sweden with Cory Straub, Assistant Professor of Biology.
The collaborative study lasted seven weeks and was conducted in an organic barley crop in central Sweden. Under Straub’s guidance they looked at the target pest called the bird-cherry oat aphid (Rhopalospihum padi). “This pest is preyed upon by a wide range of predatory insects and spiders,” said Nagy. They investigated the impact of the generalist predators Pardosa spp., Poecilus cupreus, and Bembidion spp. on R. 16 padi and hand-built the cages where they compared high-predator diversity communities to low-predator diversity communities in the presence and absence of weeds. The bird-cherry oat aphid (or R. padi) population growth was monitored and the students collected all surviving predators with pitfall traps. In the end, they found that there was no evidence that the greater biodiversity found on organic farms influences the population growth of that pesky R. padi.
Straub’s research at Ursinus looks at the effects of polyculture (growing multiple plant types together) and naturally occurring predatory insects on the potato leafhopper (PLH), a serious pest of numerous crops.