Potato leafroll virus net necrosis: identifying pest management tradeoffs among inoculation interval, storage length, and tuber weight

In the Columbia Basin region of the Pacific Northwest, the green peach aphid, Myzus persicae (Sulzer), is the predominant vector of the potato leafroll virus to potato plants, Solanum tuberosum L. Potato plants inoculated with the virus may develop tubers expressing net necrosis before or during storage, which can significantly reduce a crop's commercial value. In the field, prophylactic pesticides have been used traditionally to suppress aphid populations, thereby preventing inoculation and the advent of net necrosis. Out of the field, storage management of infected tubers has played a key part in managing the incidence of net necrosis. To identify potential tradeoffs between costs of spraying pesticides to control aphid populations and marketing activities involving storage management, data are analyzed from an extensive USDA-ARS field experiment. A probit model corrected for spatial correlation is used to predict the probability that individual tubers expressed net necrosis. The model is jointly conditioned on the inoculation interval (which is the time after planting that a plant was inoculated by viruliferous aphids), the tuber storage period, and the tuber weight. Consistent with previous empirical work, over the inoculation interval the probability of net necrosis monotonically increases to a maximum at approximately 90 d and then tends to decrease thereafter. The empirical model reveals new results, showing that net necrosis probabilities increase with longer storage periods and are notably higher for larger tubers. Jointly, these findings enable us to identify pest management tradeoffs that can help reduce the incidence of net necrosis to acceptable levels