Keywords : Onion, downy mildew, Peronospora destr uc tor foli a r applicatio n, fungicid es
IntroductionTo prot ec t onions agai ns t down y mi ldew ( Peronos pora de s tructor ) in Czechoslovakia the range of preventative treatments have until rec ently included onl y prev ent ative, conta ct fungicid es (mancozeb , zineb , copper oxychloride and zi neb + copper oxyc hlo ri de) which are often not very e ffective . Systemic fungicide s with curative properties , mai nly me t a la xy l ( 1, 2, 4, 5), cymoxanil (3) a nd fo se tyl-Al have been t es t ed agai ns t Oomy cetes since th e l a te 1970' s . The ai m of the work desc ribed here wa s to compa r e the e ffi cacy of mancozeb and zin eb with that of s ome ne we r fungicid es . M e thods The experi ment s were establis hed at the Vegeta bl e Researc h Station, Svet l a Hor a ( North e rn Moravia, Cz ec ho s lovaki a) . In one experi ment onion sets ( cv. Vsetana) we r e planted in plot s cons i s ting of four row s 4 m l ong and 30 em apa rt, with 60 em between rows of ad joining plot s . Forty onion sets were pl a nt ed at 10-cm interval s in eac h row on 15 M ay 198 5 . In a seco nd ex per iment establis hed on the same dat e, mothe r bulb s (£Y. Vsetana ) we r e planted into plots of three rows 4 m long, 30 em apart and with 90 em between rows of ad joining plots . Each row comprised 10 onions s pac ed 40 em apart . The re wer e four replications of each of the tr eatment s s hown i n Tab l e 1.