Effect of simulated rain on the efficiency of fungicides in potato late blight and early blight control

Resumo

Rainfastness of fungicides used in the control of late blight (Phytophthora infestans) and early blight (Alternaria solani) of potato was evaluated under green house and laboratory conditions. ‘Agata’ and ‘Monalisa’ plants treated with fungicides against both diseases were subjected to 20 mm controlled rain simulation for 6 min at 30 min, 1, 2, and 4 h after application. Once all leaves had dried, foliar discs were transferred to Petri dishes and inoculated with the respective pathogens. The plates were then incubated in a BOD chamber for a 12-h photoperiod at 18°C and 25°C, respectively. Disease severity was evaluated by determining the area (%) of the foliar discs affected by disease on 5 and 7 days post-inoculation. The results suggest that systemic or inherent tenacity fungicides were less influenced by the simulated rain as compared to contact fungicides. An increase in drying time promoted higher control levels of both diseases, indicating a better retention and absorption of the tested fungicides.