Ensaios comparativos sobre a eficiência de fungicidas orgânicos e à base de cobre no controle da mela (Phytophtora infestans (Mont.) de Bary) e da septoriose (Septoria lycopersici Speg.) do tomateiro

Resumo

Three experiments to control late blight (Phytophthora infestans (Mont.) De Bary and septoria leaf spot (Septoria lycopersici Speg.) on tomatoes were carried out is 1956-57.

The experiments to control late blight were started in the begining of the winter of 1956 and 1957. The following fungicides were used: 1% Bordeaux mixture, 0.5% Cuprosan (Copper oxychloride), 0.5%, Cupravit OB-21 (Copper 0Xy- chloride), 0.4% Sopronox (Yellow cuprous oxide), 0.25% Manzate (Manganese ethylene bisdithiocarbamate), 0.25% Di- thane Z-78 (Zinc ethylene bisdithiocarbamate), 0.125% Phy- gon — XL (2,3 — dichloro — 1,4 — naphthoquinone), and 0.25% Ferradow (Ferric dimethyl dithiocarbamate).

The experiment to control septoria leaf spot was star- ted on the summer of 1957. The following fungicides were used: 0.5% Cuprosan (copper oxychloride), 0.2% colloidal copper “Duphar”, 0.25% Pomarsol — Z-Forte (zinc dimethyl dithiocarbamate),

A few days after the transplanting the plants on the first experiments, the weather conditions were highly favofable to late blight. Almost all plantas were killed by the fungus. The results of this experiments (Table 1) were based only on the number of the plantas killed.

The evaluation of the efficiency of the fungicides in the second experiment was done by determing the total weight of fruit harvested, percentage of commercial fruit, percentage of fruit diseased and by a point scale adapted to evaluate the degree of attack of the disease.

In the third experiment, the efficiency of the fungicides in controlling septoria leaf spot was determined by the total wheight and number of tomatoes harvested, and the percentage of commercial fruit obtained.

According to the results obtained in these experiments, manzate was the best fungicide used, being efficient in controling late blight and septoria leaf spot both in the dry and rainy seasons.

‘Where the plants were sprayed alternately with manzate and then cuprosan, and where cuprosan alone was used, showed that both methods gave satisfactory control of late blight in dry weather.