Biological Control Activity of Arthrobotrys oligospora Against Meloidogyne incognita Infesting Okra

During the present investigation, an indigenous isolate of nematophagous fungus, Arthrobotrys oligospora and its talc-based formulation (2.1×10⁶cfu/g) was evaluated to establish its biological control efficacy against root-knot disease caused by Meloidogyne incognita and its persistence in the rhizosphere of okra. Under in vitro studies, the tested fungus was able to trap the M. incognita and formed hyphal network of three dimensional rings. A positive correlation was recorded between trap formation and nematode density and time of exposure. The management of root-knot disease was achieved either by seed coating and/or soil application compared to control under both green house and micro plot experiments. Among method of applications, soil application exhibit merit over seed coating under in vivo studies. Micro plot trial, on the other hand did not show any significant difference in plant health. However, fresh green fruit yield showed significant (P>0.05) increase in yield up to 57% in the treatment that received both seed coating and soil application of fungus compared to control. It caused a reduction up to 97% in number of galls/plant and dropped nematode population up to 88% compared to control. It is suggested that A. oligospora isolate has potential to suppress root-knot disease of okra and showed ability to establish in the rhizosphere of okra plants that was confirmed by re-isolation of tested fungus from soil at the time of harvesting the experiment and attributed to good control of disease caused by M. incognita.