Effects of fungicidal rate and intra - row spacing on Cercospora leaf spot disease of groundnut (Arachis hypogaea L.) in the Sudan savanna, north-eastern Nigeria

Abstract

A field trial was conducted during 2006, 2007 and 2008 cropping seasons to evaluate the effects of four application rates of mancozeb and three intra-row spacing on cercospora leaf spot of groundnut in the Sudan Savannah zone of Nigeria. The experiment was conducted on the University Teaching and Research Farm, Faculty of Agriculture, University of Maiduguri. The  fungicidal rates were 0.8 kg a.i./ha, 1.6 kg a.i./ha, 3.2 kg a.i./ha and 0 kg a.i./ha (unsprayed) whereas the spacing comprised 20cm (S₁,) 25cm (S₂) and 30cm (S₃) for intra-raw spacing and a maintained 50cm of inter-row spacing, for an Ex-Dakar variety. Spraying was done fortnightly. The treatments were factorially combined and laid out in a Randomized Complete Block Design (RCBD) replicated three times.  Results of the work revealed that, 3.2 kg a.i./ha and 1.6 kg a.i./ha recorded the lowest incidence and severity of the disease, followed by 0.8 kg a.i./ha, while the highest was recorded on the untreated plots. The spacing of 20cm recorded the highest disease values, followed by 25cm while the widest spacing of 30cm had the lowest disease values. The results further revealed that, 3.2 kg a.i./ha, recorded the highest yield followed by 1.6 kg a.i./ha, then 0.8 kg a.i./ha and 0 kg a.i./ha significantly had the lowest yield in all the years and combined analysis. Therefore, it is recommended that Mancozeb should be applied at the rate of 1.6 kg a.i./ha for management of cercospora leaf spot of groundnut, while the spacing of 20cm, despite higher disease values, excelled in terms of yield due to higher plant population and should be adopted for the variety and similar varieties.

Key Words: Groundnut; Cercospora leaf spots; Fungicidal rate; Intra-Row Spacing; Yield