A comparison between acid seed delinting and fungicide seed treatment in controlling cotton seedling damping-off disease*

Seed decay (rot) and seedling damping-off caused by Rhizoctonia solani are among the most important diseases of cotton which result in the significant yield reduction, application of expensive and harmful chemical fungicides and most importantly contamination of soil and agricultural environment. This study was conducted to investigate the possible efficacy of cotton seed delinting in the reduction of seeds and seedlings susceptibility to the above-mentioned diseases in comparison with the commonly used fungicide. Sulfuric acid which is commonly used for cotton seed delinting at three concentrations (60%, 80% and 98%) was used in the study and two domestic cotton varieties (Sahel and Varamin) was selected for this study. The seeds were subjected to the delinting process at the library using the abovementioned concentrations following the standard procedure. The effects of seed delinting on seed rot and seedling damping-off diseases were then investigated in a greenhouse experiment where delinted seeds were sown in plastic pots containing cotton field soil pre-inoculated with the inoculum of Rhizoctonia solani in comparison with Carboxin-thiram, the commonly used fungicide for controlling the abovementioned diseases. The effectiveness of acid seed delinting and fungicide seed treatment in controlling the diseases was evaluated by determining and comparing the number of emerged and survived seedlings in different treatments 15 and 60 days after sowing. Results indicated that seed drlinting with 98% sulfuric acid was the most effective treatment and resulted in a significant reduction in both preemergence and post emergence damping-off disease of cotton seedlings in both varieties. Seed delinting with 60 and 80% acid and treating seed with Carboxin-thiram fungicide in some experiments were effective but their effectiveness was much less than 98% acid. The overall results of this study suggest that cotton seed delinting may be an important factor in cotton cultivation and can significantly increase the emergence and number of healthy seedlings.