The question of metalaxyl resistance on late blight causing pathogen Phytophthora infestans in Estonia

Metalaxyl containing fungicides are commonly used by Estonian potato growers because of their efficiency in control of potato late blight. Metalaxyl-resistant isolates have become an important part of Estonian population of Phytophtora infestans. The aim of current study was to measure the frequency of metalaxyl resistance among Estonian population of Phytophtora infestans and to test efficacy of metalaxyl based fungicides in control of potato late blight. 138 isolates of Phytophtora infestans were collected from conventional, experimental and small scale growers fields in different parts of Estonia in 2003-2005 and assessed for resistance to metalaxyl. Metalaxyl resistant, intermediate and sensitive isolates were recorded at frequency of 37.1, 45.4 and 15.1%, respectively. Statistically significant differences (P