Title

Integrated disease management of tomato late blight disease Phytophthora infestans (Mont.) de Bary

Date of Completion

January 2003

Keywords

Biology, Microbiology|Agriculture, Plant Culture|Agriculture, Plant Pathology

Degree

Ph.D.

Abstract

Tomato late blight caused by Phytophthora infestans (Mont.) de Bary is a serious disease of tomato and potato worldwide. The disease causes severe crop losses in the tomato growing regions of the world. Most of the cultivars grown in the world are reported to be susceptible to late blight. The present study was carried out to minimize help fungicide use through integrated pest management (IPM). ^ The bio-pesticides Azadirachta indica (Neem), Artemisia vulgaris (Mugwort) and Trichoderma viride (fungus) were tested, along with the fungicides Krilaxyl (metalaxyl 8% and mancozeb 64%) and Dithane M-45 (mancozeb 80%) in Nepal during 2000 and 2001. All three bio-pesticides were found to be more effective than the control in reducing development of the disease and they increased yield over the control by 17 to 41%. However, both the fungicides were observed to be even more effective. ^ Two cropping periods, normal and 3 weeks after normal, were tested against the presence of late blight and its effect on yields. Lower disease incidence and better yields were observed to occur after the second planting. ^ Eighty tomato genotypes were evaluated against late blight under field conditions in Nepal and under laboratory conditions at the University of Connecticut. Seven to 12 genotypes were rated as resistant, 13 to 27 as moderately resistant and 34 to 43 as susceptible. For resistant genotypes, correlations between field and laboratory testing were significant and positive. ^ One hundred and three tomato isolates of P. infestans were collected from 15 districts of Nepal. All the isolates were found to be A1 mating type. Fifty isolates tested for metalaxyl sensitivity at 5 and 100 ppm were found to be sensitive to metalaxyl. ^ In conclusion, late blight disease can be controlled using bio-pesticides and fungicides. Use of bio-pesticides can help reduce use of fungicides and resulting environmental pollution. If the cropping period is shifted 3 weeks later than normal planting in Nepal, the disease can also be significantly reduced. Tomato genotypes identified as resistant and moderately resistant to late blight can form the basis of breeding programs that will yield cultivars with superior resistance in the future. ^