Integrated management of potato late blight (phytophthora infestans) (Mont.) de bary with emphasis on cultural control in the highland tropics of Ethiopia

The effects of 0.5%, 2%, 4%, 6% and 8% concentrations of crude garlic extract and 0.1% fungicide Macozeb (Dithane M 45) have been tested against the growth of mycelia, germination of zoospores and sporangia of Phytophthora infestans at Holetta (Ethiopia) during 2004 crop season. The result prevailed that, all concentrations significantly (p0.05) inhibited the growth of the fungus and germination of zoospores and sporangia compared to the negative control. The effects of time of applications of 2% garlic extract on pathogen infection showed curative effect and hinder the development of P. infestans when it was applied at a time and one day before inoculation. The severity of the disease was significantly (p0.05) higher in monoculture potato compared to intercropped with galic, faba bean and barley. At Holetta, potato variety wechecha intercropped with garlic, faba bean and barley. At Holetta, potato variety wechecha intercropped with garlic, or faba bean or barley gave 17.1%, 12.0% and 10% more over the monoculture potato without fungicide spray treatment respectively. The same intercropped treatments also were comparable and gave 10.2%, 4.6% and 2.4% advantage over monoculture potato with fungicide spray treatment respectively. Intercropping of potato with garlic at the ratio of 1:1; 1:2; 1:3; 2:1 and 3:1 had significant (p0.05) differences among potato varieties with regard to the disease development and tuber yield. Among the proportions, 75% garlic with 25% potato (3:1) intercropped plots showed significantly (p0.05) low disease development, gave higher tuber yield, land equivalent ratio (LER)1 and high monetary value at both testing sites. Intra row intercropping of garlic with potato at the ratio of 1:1; 1:2; 1:3; 2:1 and 3:1 had significant (p0.05) differences among potato varieties and treatments. Potato with garlic intercrop treatments had low disease progress compared to monoculture potato. However, the incidence of tuber rot significantly increased in intercrop treatments compared to monoculture potato. In an integrated late blight management in which intercropping of potato with garlic as a major component in the potato production system the highest (73.3%) disease control have been obtained when intercropped treatment was supported by one fungicide spray, when garlic foliage pruned two times and 2% crude galic extract spray reduced the severity of the disease by 50% compared to the monoculture potato treatment. Integrated late management gave LER1 and high monetary value over the monoculture treatment. The findings of these studies suggest garlic as potential intercropping plant for the management of potato late blight disease under Ethiopian condition.