evaluation of six fungicides for the management of nurseries apple seedling decline in 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 10 ppm against p. mercuriale (89.3%), while at 100 and 250 ppm the values were 70.06% and 75.30% for p. ultimum, respectively. the dose 2000 ppm of mancozeb completely inhibited the mycelial growth of p. mercuriale and p. ultimum. however, fosetyl-al applied at 2000 ppm revealed an inhibition percent of 51 and 100% for p. ultimum and p. mercuriale, respectively. regarding hymexazol, the highest inhibition rates were against p. mercuriale (100%) and p. ultimum (90.55%) for 60 ppm. chinosol revealed to be effective against p. mercuriale for all doses. it was effective against p. ultimum at 50 ppm (90.96%). the highest inhibition rate (86.59%) exhibited by metalaxyl-m was for p. ultimum at 120 ppm. in vivo test showed the efficacy of fosetyl-al, metalaxyl-m + mancozeb, and chinosol to reduce root browning due to p. ultimum by 55.67%, 44.33%, and 55.67%, respectively, and improved the aerial part sanitary states of seedlings inoculated by p. mercuriale by 60.06, 49.85 and 49.85%, respectively. the chinosol improved the sanitary states of the aerial part of seedlings inoculated by p. ultimum.