Control of Phytophthora palmivora on orchids with some new systemic and standard fungicide
1983
Lim, Tong Kwee | Nio, Huat Lam
Three new sy stemic fungicides viz. Aliette (efosite-A l), R idomil (m eta la xyl) and Ridom il M Z (metalaxyl plus mancozeb) were screened against tw o standard fungicides viz. Terrazole (etridiazole) and\ D ifolatan (captafol) for prophylactic and therapeutic efficacy against Phytophthora palmivora on orchids. Terminal shoots of Aranda Christine hybrids were effectiv ely pro tected from Phytophthora in fectio n w hen sprayed w ith m eta la xyl at 0.05% a.i., metalaxyl-m ancozeb mixture at 0.15% a.i. and captafol at 0.2% a.i. three days before artificial inoculation. E tridiazole and efosite-A l, b oth at 0.1% a.i. did not give adequate protection. M etalaxyl (0.05% a.i.) and its m ixture with m ancozeb (0.15% a.i.) retarded significantly disease d evelo p m en t b y Phytophthora when used as a curative spray. E tridiazole (0.1% a.i.) and efo site-A l (0.1 a.i.) gave moderate therapeutic control while captafol gave no therapeutic control. No phytoxicity was observed w ith R id o m il MZ, Terrazole and A lie tte up to concentrations o f 0.5%o a.i., 0.4%> a.i. and 0.8 a.i. respectively. The R id o m il products, A lie tte and Terrazole exh ib ited similar rates of inhibition o f linear exte n sio n o f P. palmivora b u t d iffered in the degree of in vitro fu ngi toxicity . The R idomil products and Terrazole had ED so values o f less than 1 p g /m I w hile difolatan was relatively less toxic.
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