Application of mycofungicide to control late blight of potato

Abstract

Late blight of potato in northern Thailand is caused by Phytophthora infestans and leads to economic damage in large areas of potato planted. The pathogen infects all stages of plant growth which show symptoms of late blight, stem rot and tuber rot and can result in 100% yield loss even with the use of chemical fungicides. Laboratory based bi-culture antagonistic tests showed that Chaetomium mycofungicide inhibited pathogen growth by more than 53% over 10 days. In field trials, we used a Chaetomium-mycofungicide for disease control in combination with biological fertilizers comprising 12 effective strains of cellulose degrading fungi and specific fungi for plant growth stimulants. The mixture significantly reduced disease indices in infected fields when compared with the non-treated control and the difference between Chaetomium-mycofungicide and chemical pesticide treated fields was not significant. Three Chaetomium-mycofungicide/biological fertilizer treatments were tested and compared with no treatment and a chemical pesticide treatment. Bio-technique 1 reduced late blight incidence by 34% and pathogen colonization by 56.5% leading to an increase in yield of 49%. Bio-technique 2 reduced late blight incidence by 15.5% and reduction colonization by 29% leading to an increased yield of 49%. Bio-technique 3 reduced late blight incidence by 19% and pathogen colonization by 29% leading to an increased yield of 45.5%. Chemical pesticide treatment reduced late blight incidence by 34.5% and pathogen colonization of 51.5% leading to an increased yield of 52.5%. Non-treatment gave the lowest yield due to high late blight incidence. It is recommended that the use of Bio-IPM techniques could solve the problem of disease epidemics in the infested areas planted to potato in the cool tropics.