Spray tests for control of potato blight in the hills of West Bengal II

Abstract

1. Trials were carried out with six different fungicides, namelyCoppesan, Copper Sandoz, Copravit, Shell copper, Perenox andDithane for the control of late blight of potatoes in high rainfall areas in the hills of West Bengal. 2. The fungicides were applied at five different concentrations namely, 1,25–2,50–3,00–4,00 and 5,00 lbs in 100 gallons of water at four different intervals (14, 10, 8 and 6 days respectively). Under severe late blight conditions in the hills the disease was succesfully controlled until 136 days after planting in all test plots with different fungicides when sprayed at an interval of 8 and 6 days. The “Optimum spray interval” was found to be 8 days since there was no appreciable difference in the incidence of infection between plots sprayed at 8-and 6-days’ intervals. 3. The effect due to different fungicides, different concentrations, different intervals between spray applications and the interaction between fungicides and interval between spray applications were all significant at the 1 percent level. 4. Concentrations of fungicide had the most pronounced effect on yield. Progressive increase in concentrations of fungicides gave progressive increase in yield. 5. Shorter intervals between spray applications gave more succesful control of late blight infections on foliage. 6. Highest average yields were obtained by usingCopravit andCoppesan which gave only significantly higher yields overShell copper at 5 percent level. No significant difference in yield was noticed amongst the effect of other fungicides viz.,Copravit, Coppesan, Perenox andDithane.