Tuber yield loss assessment of potato (Solanum tuberosum L.) varieties due to late blight (Phytophthora infestans) and its management Haramaya, Eastern Ethiopia.

Abstract

Potato is the most important food security crop with a fast-growing pattern. However, its production is highly affected by potato late blight disease. Field experiments were carried out at Haramaya University in 2010 main cropping season to assess yield losses of selected potato varieties with different levels of resistance to late blight disease. Combinations of five potato varieties with different levels of resistance and five rates of Ridomil applications were used. The experiment was laid out in a factorial arrangement in randomized complete block design with three replications. The combination of moderately resistant, moderately susceptible and susceptible varieties and different rates of Ridomil applications varied significantly in yield and yield components of potato. Up to 57, 42, 39, 38 and 29% tuber yield losses were recorded from the varieties Harchassa, Chiro, Bedassa, Zemen and Gabissa on untreated plots, respectively, as compared to losses from plots protected with 3 kg ha^-1 Ridomil. The highest (23 t ha^-1) marketable tuber yield was obtained from the variety Gebissa plots treated with 0.75 and 1.5 kg ha^-1 Ridomil applications. The combinations of the varieties Gabissa, Chiro, Harchassa, Bedassa and Zemen with 0.75 kg ha^-1 Ridomil application were resulted in up to 28, 21, 18, 16 and 13% marginal rate of returns, respectively. The best management of late blight and high marginal rate of return was obtained on plots treated with combinations of all tested potato varieties and 0.75 kg ha^-1 Ridomil applications followed by 1.5 kg ha^-1 Ridomil. The lowest rate of marginal return was obtained at combinations of these varieties with the 3 kg ha^-1 Ridomil. This study revealed that reduced rates of Ridomil resulted in better management of potato late blight with high tuber yield. However, further researches at different agro-ecological zones of the country are important for preference of potato varieties and specific rates of Ridomil application.

Keywords: Late blight, Phythophtora infestans, Potato, Tuber yield loss,  Marginal rate of return