INVIVO EVALUATION OF ADJUVANTS FOR MORE EFFECTIVE CONTROL OF CELERY LEAF-SPOT (SEPTORIA-APIICOLA) AND POWDERY MILDEW (ERYSIPHE-GRAMINIS) OFWHEAT WITH FUNGICIDES

The effects of seven adjuvants (at 0, 0.5, 1.0 and 2-0 g litre-1) on t he efficacies of four fungicides at 0.5 g litre-1 were studied in the laboratory for the control of leaf-spot in celery (caused by Septoria apiicola) and powdery mildew on winter wheat (caused by Erysiphe grami nis). The most effective fungicides for controlling leaf-spot were: te buconazole + triadimenol = flutriafol > mancozeb + oxadixyl > prochlor az. However, addition of adjuvant to the fungicides gave a modified pa ttern of effectiveness. The efficacy of flutriafol was strongly enhanc ed by addition of all adjuvants, but those of prochloraz and mancozeb + oxadixyl only partially so. The tested adjuvants were mineral oil surfactant, a polymer/alkoxylated alkyl ether blend, an ethoxylated al kylphenol, an ethoxylated hexitan ester blend, an ethoxylated nonylphe nol and an alkylpolysaccharide-based adjuvant mixture. However, the ad dition of adjuvants to tebuconazole + triadimenol had a negative effec t. Of all the adjuvants tested, the nonylphenol ethoxylate and a mixtu re of mineral oil/surfactant and alkylpolysaccharides gave the highest efficacy with the fungicides, while the mineral oil/surfactant and th e alkylpolysaccharides alone were less effective. There was a positive relationship between high concentrations of adjuvants and their effec tiveness, but there were some exceptions. The most effective fungicide s for control of powdery mildew in wheat were prochloraz, mancozeb + o xadixyl and tebuconazole + triadimenol. There was a linear relationshi p between the high efficacy of the fungicide and the concentration of adjuvants to control powdery mildew; in wheat. The highest concentrati on of adjuvant (2.0 g litre-1) gave the highest efficacy for the fungi cides.