Estimation of losses caused by root rotting fungi and root knot nematodes infecting some important crops in lower Sindh and Hub, Balochistan of Pakistan

摘要

Soil-borne plant diseases caused by root-knot nematodes and root rotting fungi are a serious threat to modern agriculture. In Pakistan, no extensive research work has been done on crop losses estimation by these pathogens and pests. During the present study, survey of diseased agricultural fields, at different locations in Lower Sindh and Hub, Balochistan was carried out in different seasons to determine the losses caused by soil-borne root-rotting fungi and root-knot nematodes in some economic crops like chili ( Capsicum annuum L.), cotton ( Gossypium hirsutum L.), egg-plant ( Solanum melongena L.), melon ( Cucumis melo L.), sunflower ( Helianthus annuus L.) , tomato ( Lycopersicon esculentum Mill.) and watermelon ( Citrullus lanatus (Thunb.) Mansf.). The most common root rot pathogens found in all the areas visited were Macrophomina phaseolina, Rhizoctonia solani and species of Fusarium viz., Fusarium oxysporum and F. solani. Two species of root-knot nematode Meloidogyne incognita and M. javanica were also found causing root- knot disease. Loss to chili crop was found upto 36-56% when infected with F. solani and R. solani combined with root knot nematodes. Whereas loss to melon crop was found 30-60% due to F.solani in different areas of Thatta. Association of Fusarium spp., with root knot nematodes was found causing 50-85% loss to tomato crop. Charcoal rot caused by M. phaseolina was found to be an important disease of sunflower and cotton. Variations in losses due to these pathogens depended upon combination of pathogens and soil types.