EFFECTS OF FUNGICIDE APPLICATION FREQUENCY ON LATE LEAF SPOT SEVERITY, YIELD AND SOME PHYSIOLOGICAL PARAMETERS OF GROUNDNUT.

Abstract

In 2016 cropping season, a trial was conducted to evaluate fungicide application frequency in the management of late leaf spot of groundnut induced by Phaeiosariopsis personata (Berk, & M. A. Curtis van Arx) in Samaru, North-West Nigeria. SAMNUT – 14, a variety of groundnut susceptible to the disease was subjected to five different frequencies [plants sprayed weekly (T1), plants sprayed biweekly (T2), plants sprayed every three weeks (T3), plants sprayed every four weeks (T4) and unsprayed plants (T5)] of fungicide application. The experiment was in a Randomized Complete Block Design (RCBD) with three replications established at the Institute for Agricultural Research (IAR) Farm Samaru, Zaria. Natural infection in the field was relied upon as the source of inoculum. The parameters recorded were stand count at emergence, and at harvest, disease severity at 56, 63, 70, 77, 84, 91 and 98 Days After Sowing (DAS) based on 1 – 9 scale, Area under Disease Progress Curve (AUDPC), percent defoliation, pod and haulm yields, crude protein content and chlorophyll content were also computed. The results showed that spraying weekly was found to be most effective in reducing disease with minimum disease severity of 33.33 % and improved pod yield by 47.91 %. Biweekly application of the fungicide was also found to be effective with decrease in disease severity by 56.41 % and increase of 45.65 % in yield over untreated; and was most economical with cost: benefit ratio of 1:69.6. Crude protein and chlorophyll contents increased by 29.45 % and 78.57 % in the treated plants respectively compared to the untreated. It can be concluded from this study that spray of mancozeb + carbendazim at biweekly interval was the best economical management option for late leaf spot of groundnut.