Skip to main content
CORESTA Meeting, Agronomy/Phytopathology, Suzhou, 1999, AP35

Adding metalaxyl to float water as a means of controlling blue mould in float systems

DE ROTON C.; VIDAL B.; TANCOGNE J.
SEITA, Institut du Tabac, Bergerac, France
Transplanting seedlings protected against blue mould and aphids by an uptake of endotherapic ingredients is a means of preventing early infestations and reducing the number of treatments in the field. In an experiment, conducted in 1998 at the Bergerac Institute, in the autumn in order to avoid contamination from other experiments, metalaxyl (Acylon), at doses of 1.25, 4 and 6 mg, combined with 3 mg imidacloprid per plant, was added to the nutritive solution of a float system with seedlings of Virginia tobacco. There was an untreated check and two replications of each variant in the experiment. During plant growth, phytotoxicity symptoms were observed for doses >= 4 mg metalaxyl, but this did not affect the percentage of usable seedlings. After transplanting into pots, checks were introduced at 7-16 days intervals in a greenhouse contaminated by plants bearing blue mould, to check the permanency of the inoculum. The first symptoms of blue mould appeared on checks 11-13 days after their introduction in the greenhouse, suggesting an immediate contamination. The disease peaked after 17-21 days and the plants died at 22-45 days. On treated variants, introduced in the greenhouse in two times at 8 days interval, symptoms appeared after 40-51 days, i.e. 30-40 days after they appeared on the checks, and the higher the metalaxyl concentration, the later the appearance of symptoms. Peronospora strains taken from the checks and treated terms were not metalaxyl-resistant. This method is simple and environment-friendly, however, compared with sprays, it uses a lot of metalaxyl. The doses used, which in their upper range proved to be phytotoxic, will be reduced in future trials.