CHEMICAL CONTROL OF PHYTOPHTHORA-NICOTIANAE ON TOMATO ROOTS WITH FOSETYL-ALUMINUM IN HYDROPONICS

Phytophthora nicotianae often has been isolated from tomato plants. It causes a foot and root rot, especially in hydroponic systems. Yield l osses in this trial reached 39 per cent. The purpose of this study was to determine the effectiveness of the fosetyl-aluminium application a gainst the pathogen and its suitability for control in hydroponic syst ems. Leaf applications, preventive and curative applications were prov ed to be effective and the effectiveness of fosetyl-aluminium and meta laxyl in vivo were also compared. In addition the practical approach o f applications was investigated: the longevity of protection after one preventive application, the frequency of applications and the applica tion of fosetyl-aluminium in nutrient solutions or in water. The effec tivity of applications was measured by the disease progress, tomato yi eld and other plant growth parameters. Two curative applications of fo sethyl-aluminium with 800 mg/l provided an effective control for 21 da ys and one preventive application was more effective for about 50 days . The control could be ensured and improved by a second application af ter, at the earliest, 14 days. Fosetyl-aluminium was applied in the re circulating tap water for about 24 hours. After that, a constant suppl y of nutrient solution was provided. There was no negative effect of f osetyl-aluminium on the yield and plant growth of the tomato. On the c ontrary, inhibition of stem growth was not detected at all. In most ex periments, root development was also supported by the treatment. Durin g the comparative investigations, two fosetyl-aluminium applications I n an interval of 14 days showed nearly the same activity like two prev entive applications of metalaxyl with an interval of 21 days and much more activity than two curative application with the same interval of the same active substance.