EFFECT OF VARIETY AND FUNGICIDE FREQUENCY ON THE MANAGEMENT OF TOMATO LATE BLIGHT (Phytophthora infestans (MONT) DE BARY) IN BOMBE WOREDA, WOLAITA ZONE, SNNPR, ETHIOPIA

Abstract

Diseases are the major constraints that limit production of tomato in Ethiopia. Late blight is a very severe disease in most tomato growing regions, including in Wolaita zone, where information on disease management options through integration of varieties and fungicide applications are poor. Aim of the present study was therefore, to determine frequency of fungicide spray with respect to host resistance level on the management of late blight of tomato. A field experiment was conducted at Frwocha kebele in Boloso Bombe Woreda during 2019 cropping season. The experiment was laid using RCBD in factorial arrangements with three replications. The treatments consisted of four foliar spray frequencies, and three tomato varieties (Melkasalsa, Metadel and ARPTd2). Important parameters collected were incidence and severity of late blight, and growth and yield related traits of tomato. Significant variations were observed among varieties in reducing late blight of tomato and increasing the fruit yield. The highest late blight severity and AUDPC (43.2 and 629.81, respectively) were recorded from variety Melkaslsa, and the lowest (32.59 and 441.61, respectively) were recorded from variety ARPTd2. Interaction of varieties and fungicide spray frequencies did not show significant difference on most components of late blight epidemics, crop growth and yield related parameters. However, significance differences were observed on marketable and total fruit yield. The maximum marketable (61.70) and total fruit yield (67.30) were recorded from plots treated with three and two time sprayed on ARPD2 tomato variety, respectively, while the lowest marketable (24.06) and total fruit yield (35.43) were recorded from unsprayed plots of Melkasalsa and Metadel varieties, respectively. Correspondingly, the highest disease progress rate of (0.09) was obtained in unsprayed plot of the variety Melkasalsa; however the lowest disease progress rate of (0.04) was recorded from the plots of ARPTd2 and Metadel variety treated with Ridomil four times at 7 days interval. Fruit yield loss of up to 47.04% was calculated on unsprayed plots as compared to highly treated plots. On the other hand, marginal analysis indicates that the highest 87.94% marginal rate of return in comparison with unsprayed plots was obtained where ridomil sprayed two times on ARPTd2 variety as compared to other spray frequencies. In conclusion, integrations of varieties and two times foliar spray of ridomil on ARPTd2 variety were found to be an effective treatment in reducing tomato late blight epidemics and increasing fruit yield. Moreover, ARPTd2 variety appears to have comparative resistance to late blight and is a promising tomato variety. However, further investigation should be carried out for developing concrete recommendation for late blight management options through integration of varieties and fungicide spray frequency that may contribute to sustainability by stabilizing tomato production in the country.