The development pattern of Dothistroma needle blight and its control

Abstract

From field investigations and inoculations, Dothistroma pini, the pathogen of Dothistroma needle blight was found to overwinter as mycelium and unmaturcd acervuli in infected needles. The conidia were spreaded mainly by rain splash. The disease became widespread by transporting diseased seedlings and scions, conidia spread throughout the growing season, but mainly from May to July. The disease was found in both stand locations in each summer of investigation. The outbreak severity was serious in pure stands of susceptible pine and mixed stands with large components of susceptible pine, but slight in mixed stands of unsusceptible species with small components of susceptible hosts. The disease was less severe in pruned stands than in unpruned stands. The disease was most serious near the infection centre, indoor and outdoor tests, it was shown that Chlorothalonil smoke, Chlorothalonil spray and Thiram and Asomate sprays were effective control fungicides.