Miseda Victoria Onyango^1,, Wanyera Ruth², Muthamia Japhet³, Owuoche James¹

Stem rust (Puccinia graminis f.sp tritici) of wheat (Triticum aestivum L.) is a major threat to wheat production. The objective of the study was to determine the effects of fungicide on the development of stem rust infection. Kwale cultivar was grown in the field at KALRO-Njoro in a Randomized Complete Block Design (RCBD) split-plot arrangement for main-rain (June to November, 2014) and off-rain season (February to May, 2015) by applying three treatments of Fosphite 53 SL (Monopotassium + dipotassium 530 g a.i. L^-1) (5L ha^-1, 7.5L ha^-1, 10L ha^-1), untreated plot and a standard check (Folicur 25 EW at 2.5L ha^-1) at three different growth stages of the wheat cultivar Kwale. Evaluation of disease severity was based on the modified Cobbs scale and expressed in terms of Area Under Disease Progress Curve (AUDPC). Data on yield and yield components were taken at harvest and analyzed using Statistical Analysis System (SAS) and the mean comparisons based on Least Significant Difference (LSD) at 5% probability for the separation of season, growth stage and fungicide rates. There was significant (P≤0.05) effect (season × crop stage) for AUDPC-YR and (P≤0.001) for plant height. Main-rain season, 2014 had higher values for AUDPC-SR and AUDPC-YR at 40.579% and 36.777% and lower values for plant height, tillers, spike length, spikelet per spike, TKW, biomass and yield by 17.127%, 36.874%, 19.543%, 1.27%, 3.26%,39.263%, and 40.148%, respectively compared to off-rain season, 2015. Tillering stage had lower values for AUDPC-SR and AUDPC-YR by 3.41% and 17.617% and high yield and grain weight as compared to stem elongation and heading stage. Of all the tested rates of Fosphite 53 SL (Monopotassium + dipotassium 530 g a.i. L^-1) only the rate of 0.5L ha^-1 showed significant reduction in the disease pressure and positive influence in the yield and grain weight. The results suggest that spraying of Fosphite 53 SL at 0.5L ha^-1 at tillering stage is effective in controlling stem rust hence, the adoption of effective fungicides to control stem rust pathogen and their application at the right stage of the crop can be used in reducing stem rust severity and increase yield of susceptible wheat cultivars in stem rust occurring areas.

cultivar, fungicide, stem rust, wheat