The effectively test of the metalaxyl on different concentrations and application intervals to Phytopthora infestans that caused potato late blight in the wet season in the Karo highlands

Abstract

Potato (Solanum tuberosum) is short-lived annual crops of high economic value tubers. In the cultivation of potato plants there are many problems faced by farmers. One of which is potato leaf blight caused by the fungus Phytophthora infestans is one of important pathogen in potato crop. This research was conducted in the Plant Disease Laboratory, Faculty of Agriculture Universitas Sumatera Utara and in Karo District of North Sumatra (wet season). Two tests were done, in vitro and in the field, respectively. In vitro test used a non factorial Complete Randomized Design with active ingredients concentration of Metalaxyl 50ppm, 75ppm and 100ppm and in the field was done with factorial Randomized Block Design with 2 factors: the first factor was the concentration level of fungicide 0g/l, 2g/l, 3g/l, 4g/l and the second factor was spraying intervals of 4 days, 8 days and 12 days. The results showed that the in vitro test at a concentration of 100 ppm could inhibit fungal growth by 22.98% and the metalaxyl field test and application interval ineffective to inhibit P. infestans fungal infection and the damage reached 100% in control trials at 66 days after planting.