Cucumber Response to Target Blot as a Result of the Effect of Products on Disease Control

Abstract

Target spot, caused by Corynespora cassiicola, occurs in several cultivated species, being considered an important disease in cucumber. The objective was to evaluate the cucumber response to the target spot as a function of preventive management of the disease with fungicides and phosphites, associated or not with silicone adhesive spreaders. 'Soldier' cucumber plants were grown in 10 L pots in a greenhouse. Chlorothalonil and methiram + pyraclostrobin fungicides and potassium and zinc phosphites were evaluated, combined or not with Silwet L-77 Ag® and Break-Thru® adhesive spreaders, applied four days before pathogen inoculation. The severity of the disease was evaluated; the fresh and dry mass of the aerial part of the plants at 60 days after sowing; the number and fresh mass of fruits, and the number of leaves and plant height at intervals of 7 to 10 days from the inoculation of the pathogen. Fungicides were more efficient in controlling target spot, followed by zinc phosphite, while potassium phosphite did not differ from the inoculated control, which reached severity greater than 40%, 10 days after inoculation of the pathogen and more than 75% of dry leaves (2nd and 3rd true leaves), 25 days after inoculation. Greater fresh mass of the aerial part of the plants was observed with the fungicides, with no difference between the treatments for the other variables. Adhesive spreaders had no effect on the analyzed variables. Cucumber production was not affected by treatments up to 60 days of cultivation, despite the disease intensity being lower with fungicides and zinc phosphite.