Weed Hosts of Root-Knot Nematodes and Their Distribution in Fiji

Weeds can act as reservoir hosts of a range of pests and diseases. Information and knowledge on the host status of weeds to common pests and diseases can be used to develop integrated weed and pest management strategies. As part of a survey on the distribution and diversity of root-knot nematodes on crops in Fiji, the root-knot nematode host status of weeds was also studied. Weeds growing in root-knot nematode infested farms (N= 189) and bioassay pot soil samples (N= 277) were identified and their host status was determined on the basis of a root gall and egg mass index scale from 0-5. A total of 45 weed species were recorded as potential weed hosts of root-knot nematodes with a gall index from 1-5. Using the weed and tomato bioassay method, a total of 11 non host weed species were recorded with a gall index of 0, relative to infected tomato growing in pot soil samples. Common weeds infected by root-knot nematodes on farms and in bioassay pot soil included slender amaranth, old world diamond-flower, tropic ageratum, sicklepod, mimbra, balsamapple, purple bushbean, little ironweed, ivy gourd, and cutleaf groundcherry. The presence of egg masses on the weed hosts indicates their ability to sustain root-knot nematode populations thus their potential to act as reservoir hosts.