The relation of potato leaf roll virus net necrosis in potato tubers to the interval between planting and inoculation

Abstract

The green peach aphid, Myzus persicae, is a vector of potato leaf roll virus. Inoculated potato plants may develop tubers expressing net necrosis at harvest or in storage, which can significantly reduce the crop's commercial value. Insecticides have been traditionally used in a prophylactic manner to suppress the aphid population in the field thereby preventing inoculation and the advent of net necrosis. To analyze the rationale of such an insecticide application decision, data generated by two field experiments were used to establish an empirical relationship between the probability that a tuber will express net necrosis (NN probability) and the time after planting that inoculation occurs (inoculation interval). In contrast to past studies, the data analyzed here allow for the investigation of the impact of inoculation dates occurring over the entire growing season. This uncovers the previously unknown empirical result that NN probabilities may peak before monotonically declining in the second half of the growing season. It implies that insecticide spraying might profitably be concentrated on inoculation intervals generating peak probabilities, to ‘flatten’ the peaks to acceptable probability levels. The data also permitted a limited analysis of the systematic ways that increasing storage periods may alter the empirical relationship between NN probabilities and inoculation intervals.