Two experiments were carried out under field conditions at UNESP/FCAV, Jaboticabal, São Paulo state, Brazil. In the first experiment (from May to October, 1993) the efficiency of weekly sprays of sodium bicarbonate (1%), vegetal oil (1%) and iprodione (0.075%), alone or in combination, were studied for the control of tomato early blight (Alternaria solani), using tomato cv. Jumbo AG-592. In the second experiment (March to June, 1993) the efficiency of weekly sprays of different doses of sodium bicarbonate (0.5, 1 and 1.5%) were compared with benomyl (0.05%), on the control of cucumber net spot (Leandria momordicae), using cucumber cv. Premier. The experiments followed a randomised block design with four replications and forty plants distributed in four rows of 5.0 and 2.5 m long used respectively for cucumber and tomato. Disease severity on tomate was rated at 14 day intervals (the first five) and at 7 day intervals (the last two), beginning 39 days after transplanting. Disease severity for cucumber net spot was rated five times, at 14 day intervals, beginning 28 days after transplanting. Disease progress curves for each treatment for each culture were determined. Fruit yield for each culture was also evaluated. Results showed that evaluation of disease severity in the fifth leaf and logistic transformation were most suitable for the study of tomato early blight epidemics. For cucumber net spot, evaluation in the fourth leaf and logistic transformation were the most suitable, as shown by the determination coefficient values. Both iprodione and sodium bicarbonate provided efficient early blight control, with no statistical differences between them. For cucumber net spot, the fungicide benomyl decreased the infection rate of the epidemic whilst sodium bicarbonate had no effect. The results indicate that sodium bicarbonate and vegetal oil have a potential for early blight and net spot control, although further studies are required.
Lycopersicon esculentum; Cucumis sativus; Alternaria solani; Leandria momordicae; iprodione, benomyl; regression
