Efficacy of different fungicides against tomato late blight disease

Abstract

Tomato (Solanum lycoperscum) is one of the most important vegetable crop in Uganda .Diseases are the major constraints that limit production and quality of tomato of which late blight caused by Phytophthora infeestans is the most sever and economically important. Late blight is responsible for up to 100% yield loss. Tomato growers in Uganda use fungicides to reduce yield loss due to late blight. Unfortunately, these are mostly used indiscriminately and excessively, and this brings about human and animal health and environment pollution concerns in addition to development of pathogen resistance to such chemicals. There is less vital information about the various fungicides on the market. Therefore, a field experiment was conducted at Makerere University Agricultural Research Institute Kabanyolo (MUARIK) during 2018 main cropping season to evaluate the effectiveness of different fungicides against P. infestans, establish the optimum fungicide frequency in managing late blight and to promote judicious use of fungicides in tomato late blight disease management. The treatments consisted of four foliar fungicides (Victory 72 WP, Toplite, Azoxystrobin and mancozeb 80% WP) applied to two tomato varieties (MT56 and Tengeru 97) under two spray frequencies and were laid in a factorial design under a split-split arrangement with three replicates. To achieve the objectives of the study, data on severity of late blight on stem and other foliar parts, fruit disease severity were collected and recorded. At maturity, ripe fruits were harvested at a weekly interval and yield weight recorded in terms of marketable, unmarketable and total fruit tomato yield. The means of the data collected were then analyzed and then separated by the least significant difference (LSD) at test P=0.05. Results indicated that all fungicide applications under different frequencies significantly controlled late blight. Fungicides showed variations in efficacy over disease control when sprayed at different frequencies. Victory 72 (metalaxyl+mancozeb) application had the highest efficacy over late blight control both at 7-days and 14-days spray intervals followed by Toplite (9% dimethomorph + mancozeb 64%), Azoxystrobin and mancozeb 80% WP. With respect to total fruit yield of tomato, plants sprayed with Victory 72 WP demonstrated high fruit yields compared to other fungicide applications both under reduced and increased spray frequencies. Mancozeb 80% WP had the lowest efficacy on lesion development under reduced spray frequencies. Tomato variety MT56 was less susceptible to late blight disease compared to Tengeru 97 variety.