Pratylenchus on Ginger in the Himalayas: Alternate Hosts and Survival Between Crops

Crops and weeds were surveyed at Denchong, Sikkim and Kalimpong, West Bengal, to determine the importance of soil borne inoculum of lesion nematodes, Pratylenchus spp., particularly Pratylenchus coffeae, a major pathogen of ginger, causing foliar yellows and rhizome dry rot. Populations of Pratylenchus fell sharply in soil after harvest of ginger, but were detected at low levels (c. 20 per 250 cc soil) for 2 years at Denchong and 3 years at Kalimpong. A majority of the roots sampled from crops and weeds examined contained Pratylenchus species, although frequency of isolation and numbers varied between samples. Importantly, maize (Zea mays) and legumes (Glycine max, Phaseolus vulgaris and Vigna umbellata), the dominant crops in the rotation between successive plantings of ginger, as well as the common weeds Galingsoga parvijlora and Blainvellia sp., were hosts. Five Pratylenchus species were identified: P. brachyurus, P. colleae, P. flakkensis, P. pratensis and P. zeae, P. colleae was present in the roots of Saccharum edule and Commelina benghalensis, and possibly Brassica campestris var. toria, Phaseolus vulgaris and Solanum tuberosum, but not in maize.