Influence of Temperature on Effectiveness of Hardlock Disease Management.

In the southeastern US hardlock is a serious problem associated with cotton production. Hardlock is a failure of the fiber to expand outward from the locules after boll opening. Research has demonstrated the fungal pathogen Fusarium verticilloides to be associated with this problem. Research was conducted during the 2002-2007 growing seasons to determine the efficacy of fungicide treatment to control hardlock in cotton. Artificial inoculations of flowers with Fusarium verticillioides were carried out in field and in greenhouse (2008). Fungicide applications, (thiophanate-methyl), to cotton during bloom have been shown to reduce the problem. Fungicide applications were most effective in years with moderate to severe disease pressure. Years with low disease pressure and smaller treatment differences were associated with relatively low temperatures during the first 40 days of bloom. Lint yield and severity of hardlock is inversely proportional to each other. This study indicates that there is a significant impact of temperature on the effect of the application of fungicide against hardlock of cotton.