Agrotechnology

Abstract

Effect of Varieties and Fungicides on Potato Late Blight (Phytophthora infestans, (Mont.) de Bary) Management

Shiferaw Mekonen and Tesfaye Tadesse

Late blight of potato which is caused by Phytophthora infestans, (Mont) de Bary is an important disease of potatoes (Solanum tubersolum) and is a prevalent disease in all potato producing areas of Ethiopia. A field experiment was conducted for two consecutive years (2016 and 2017) under the main rainy season to develop integrated management options for late blight disease of potato at Bursa District, Sidama Zone, SNNPRS, Ethiopia. Two improved varieties having different level of resistance, four registered fungicides, and two unsprayed plots (control) were arranged in a factorial randomized complete block design with three replications. The result showed that all fungicides significantly reduced the infection of late blight as compared to the unsprayed treatments at both seasons. Two way interaction of variety by fungicide showed significant difference on controlling disease severity and increasing tuber yield in 2017. Fungicides Matco (Metalaxyl-8%+Mancozeb-64%) and Boss (Metalaxyl+Mancozeb) 72% WP significantly reduced severity of the disease as compared to Bacticide (Copper Hydroxide) and Mancozeb (Diathane-M45) in 2017 cropping season. Whereas in 2016 the disease pressure was low as the result there was no significant difference between fungicides. Depending on the fungicides efficacy and varietal reactions to the disease (21.82 to 30.47 t ha-1) and (20 to 36.84 t ha-1) tuber yield were obtained from the sprayed plot in 2016 and 2017, respectively. On the other hand from unsprayed plots, 10.63-18.63 t ha-1 and 8.8-17.4 t ha-1 tuber yield was obtained in 2016 and 2017 cropping seasons respectively. The mean yield advantage of fungicide sprayed plots for both varieties was 62% as compared to the unsprayed ones. The study confirmed that host resistance level and fungicide efficacy played an important role in host–pathogen–fungicide interaction to reduce the severity of late blight on potato. Therefore, it was confirmed that the combined effects of growing moderately resistant cultivars with the application of fungicides Matco at two spray frequency in 10 day intervals reduced the yield loss and damage caused by late blight even under high late blight pressure.