Potato Varietal Mixtures for Potato Leafhopper Management on Organic Farms
Project Leaders: A. Seaman, NYS IPM Program, Cornell University; W. Tingey, Department of Entomology, Cornell University; A. Power, Department of Ecology and Evolutionary Biology, Cornell University
Cooperators: D. Halseth, Horticulture Department, Cornell University; W. De Jong, Department of Plant Breeding and Genetics, Cornell University
Abstract: Organic potato growers in areas with high potato leafhopper (PLH) pressure may suffer yield losses of up to 50% in susceptible varieties due to the effects of leafhopper feeding. Organic farmers grow a diverse assortment of potato varieties of many shapes and colors, with a range of susceptibility to PLH. The Cornell potato breeding program has produced clones with high levels of resistance to PLH and Colorado potato beetle. The resistant clones are the product of a cross between a wild potato species and commercial potatoes, and the leaves have sticky trichomes that repel adult leafhoppers and trap leafhopper nymphs. The resistant clones are round white varieties, which constitute only a portion of the diverse varieties grown on organic farms to meet the expectations of the organic market, but we hypothesized that they may possibly be deployed in a way that would help protect adjacent susceptible varieties. This project was designed to determine whether planting mixtures of resistant and susceptible varieties will alter leafhopper behavior in ways that reduce populations and protect the susceptible varieties in the mixtures from damage. We tested mixtures of a highly resistant breeding program clone and a susceptible commercial variety in a replicated trial.
Many insecticides approved for organic production have not been tested against PLH. Only one approved material (Pyganic) has been found to be effective in university trials. Optimal spray timing and frequency have not been determined for Pyganic, which degrades rapidly after application, and costs $50 per acre at the rate found to be effective. We conducted a trial looking at the efficacy of Pyganic at different spray timings and in combination with Surround, a kaolin clay product.