Disease Management

Abstract

Powdery mildew of crucifers is a compound interest disease (polycyclic) whose epidemic development within the growth cycle of the host is determined by the initial amount of inoculum or primary inoculum, and the rate at which the disease/inoculum increases i.e., the apparent infection rate. To reduce the severity of powdery mildew, the reproductive rate of the pathogen must be decreased. The major contributing factors which affect the reproduction rate of pathogen are reduction in the infection frequency or lesion/colony numbers, and size, longer latent period of the pathogen, and deceased spore production. These can be controlled by spraying of fungicides soon after the appearance of the disease symptoms, and repeating of second spray at an interval of 10-days. To escape the crop from powdery mildew infection, date of planting should be manipulated to avoid congenial weather conditions, and susceptible growth stage of the crop. Out of several chemicals tested, fungicides like sulphur (wettable sulphur), Karathane, Calixin, Dinocap, flusilazole, and carbendazim have shown their efficacy against powdery mildew with positive effect on total yield, and yield contributing attributes. Some biological control agents have shown promise to control powdery mildew when used as seed treatment and foliar sprays (Allium sativum, Trichoderma harzianum, and Pseudomonas fluorescens). Cultural practices like mixed cropping with pea, and wider spacing of crop reduces powdery mildew intensity under field conditions. Crop nutrition in the form of FYM is better than chemical fertilizers to manage powdery mildew of crucifers but higher yields are obtained with chemical fertilization. Integrated disease management using all means to control powdery mildew gives better results for high yield, and better quality of crucifers.