Biocontrol efficacy of nematode trapping fungi Arthrobotrys oligospora and A. dactyloides against root-knot nematode in ginger

Fungal biocontrol is a rapidly developing research area, and there is an emergent interest in the exploration of fungi for controlling root-knot nematodes. Root-knot nematode remains one of the most serious soil-borne pathogens affecting ginger cultivations, causing considerable yield damage. Although most growers rely on chemical controls to manage root-knot nematodes, regulatory authorities no longer advise chemical usage. Hence, many researchers have examined eco-friendly control measures. In this study, two nematode-trapping fungi, Arthrobotrys dactyloides and A. oligospora encapsulated in kaolin-alginate granules were separately assessed for their efficacy in controlling root-knot nematode damage in ginger. Four weeks after planting, both fungi and chemical treatments had significantly less root-knot nematodes than control irrespective of soil sterilization. This indicated the biological control potential of these two fungi against root-knot nematodes in early growth period of ginger. At harvest, the root-knot nematode numbers recovered from both fungi treatments were lower than control but higher than chemical, although the difference was not statistically significant. In addition, the relative fungal efficiency of root-knot nematode control was not significantly different between the heated and unheated soils. This suggested that the biological factor present in the grey sandy loam soil had no distinct influence on the root-knot nematode control efficacy of these two fungi. Compared to control, application of both fungi in both soils reduced root galling and damage lesions similar to the chemical treatment. The rhizome yield, number of shoots, above ground biomass, plant height, number of leaflets and weight of feeder roots were not significantly different between nematode treatments.