Sabrine Mannai - High Institute of Agronomy of Chott Mariem, Department of Biological Sciences and Plant Protection, University of Sousse, ۴۰۴۲ Sousse, UR۱۳AGR۰۳, Tunisia.
Naima Boughalleb-M'Hamdi - High Institute of Agronomy of Chott Mariem, Department of Biological Sciences and Plant Protection, University of Sousse, ۴۰۴۲ Sousse, UR۱۳AGR۰۳, Tunisia.

Apple decline, responsible for seedlings root and collar rot in nurseries, is an important disease. Some Oomycetes species were associated with this disease. This study aimed to control this severe decline disease. The effect of six chemical products against Pythium ultimum and Phytopythium mercuriale associated with apple seedling decline was evaluated using in vitro poisoned food technique and in vivo greenhouse assays. The carbendazim was effective at ۱۰ ppm against P. mercuriale (۸۹.۳%), while at ۱۰۰ and ۲۵۰ ppm the values were ۷۰.۰۶% and ۷۵.۳۰% for P. ultimum, respectively. The dose ۲۰۰۰ ppm of mancozeb completely inhibited the mycelial growth of P. mercuriale and P. ultimum. However, fosetyl-Al applied at ۲۰۰۰ ppm revealed an inhibition percent of ۵۱ and ۱۰۰% for P. ultimum and P. mercuriale, respectively. Regarding Hymexazol, the highest inhibition rates were against P. mercuriale (۱۰۰%) and P. ultimum (۹۰.۵۵%) for ۶۰ ppm. Chinosol revealed to be effective against P. mercuriale for all doses. It was effective against P. ultimum at ۵۰ ppm (۹۰.۹۶%). The highest inhibition rate (۸۶.۵۹%) exhibited by metalaxyl-M was for P. ultimum at ۱۲۰ ppm. In vivo test showed the efficacy of fosetyl-Al, metalaxyl-M + mancozeb, and chinosol to reduce root browning due to P. ultimum by ۵۵.۶۷%, ۴۴.۳۳%, and ۵۵.۶۷%, respectively, and improved the aerial part sanitary states of seedlings inoculated by P. mercuriale by ۶۰.۰۶, ۴۹.۸۵ and ۴۹.۸۵%, respectively. The chinosol improved the sanitary states of the aerial part of seedlings inoculated by P. ultimum.

chemical control, apple decline, nurseries, Pythium ultimum, Phytopythium mercuriale