Control of cotton boll rot through selected chemicals

Abstract

An experiment was conducted at the Research Farm of Sher-e- Bangla Agricultural University, Dhaka, Bangladesh during the kharif season of 2013-2014 to study the effect of some selected chemicals to control cotton boll rot disease. The experiment was carried out under in-vitro and in field conditions. The field experiment was laid out in randomized complete block design (RCBD) with three replications. Cotton variety CB 9 was used in the experiment. Three of fungi viz: Fusarium spp., Alternaria spp., Aspergillus flavus and A. niger were isolated from seeds of cotton and diseased bolls of cotton. Sclerotium rolfsii was also isolated from infected bolls of cotton. Three chemicals namely Mancozeb, Cupravit 50 WP and Streptomycin sulphate were used against the fungi. In in-vitro test combined effect of Mancozeb and Cupravit 50 WP (0.4%) showed the best result which inhibited the radial mycelial growth of all fungal species followed by Cupravit while Streptomycin sulphate showed no effect on mycelial growth. In field condition, seed treatment with Mancozeb + Cupravit 50 WP (0.4%) along with three foliar sprays proved to be most effective to control boll rot of cotton followed by seed treatment with Cupravit 50 WP (0.4%) along with foliar spray for three times. Seed health study of harvested cotton seeds revealed that seed treatment followed by foliar spray with Mancozeb + Cupravit reduced the incidence of seed borne fungi partially compared to control. In all the cases Streptomycin sulphate (0.1%) showed no significant effect.