The effect of mixed cropping systems on winged aphid dispersal and potato vVirus Y spread in organic seed potato

Potato virus Y (PVY) is a major limiting factor for the production of organic and conventional certified seed potatoes in the Midwest. PVY is transmitted by aphids in a nonpersistent manner and continues to be a problem for seed potato production because infected plants often do not exhibit obvious symptoms yet produce infected tubers which result in yield losses in the following growing season. Intercropping and crop mixture systems have been shown to reduce the incidence of nonpersistent insect-borne viruses in other agricultural crops and may be useful strategies for minimizing the spread of PVY in organic potato fields. In 2009, a field trial was conducted at a certified organic field site in Wisconsin to compare aphid landing rates and PVY incidence among different cropping practices. Combinations of cover crop and intercrop treatments were assigned in a complete randomized block design to an area of 0.24 hectares planted to potato (certified at 1% PVY incidence). Horizontal water pan traps were used to monitor weekly aphid landing rates and serological assays were used to estimate the incidence of PVY in harvested potato tubers. A total of 1512 winged aphids were captured and Aphis glycines followed by Therioaphis trifolii were most abundant over the course of the season. There was no defined relationship between PVY incidence and the cumulative sums of common aphid species among cropping treatments. We are currently examining the potential of mixed cropping systems in conjunction with other cultural control tactics to minimize PVY spread in organic seed potato.