Effects of Three Different Compost Types on Verticillium Wilt (Gossypium hirsutum L.) of Cotton under Greenhouse Conditions

Verticillium wilt is one of the most devastating diseases on cotton. This study aimed to evaluate the effect of three types of composts (derived from municipal waste [MW], crop residues [CR], or animal husbandry silage [AS]) on development of cottonVerticillium wilt under controlled conditions. Experiments were carried out as factorial randomized complete block design with 4 replications. To inoculate Verticillium dahlia, its microsclerotia were mixed in the proportions of 5 and 10 per gram of soil. Each compost type was also mixed, in the proportion of 35% (w/w) with the soil before planting. The data of plant wilting index showed that the composts reduced the disease severity and increased fresh weight of plant foliage. The results indicated that the CR and AS composts caused a significant reduction of wilting. MW compost, however, didn’t cause significant wilting reduction compared to the control. The fresh weight of plant foliage significantly increased following application of all composts. Number of fungus microsclerotia showed a significant reduction in the soils treated with composts. In vitro studies indicated slowdown of fungi growth in culture media containing extract of the CR compost. Analysis revealed no significant differences between CR and AS composts in reducing index of wilting, and the final number of microsclerotia in the soil and also in increasing of foliage fresh weight of host plant. Based on these findings, two composts of CR and AS are useful to reduce the damage of Verticillium wilt of cotton, as a part of integrated disease management, and necessitate more investigations.