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 to 5. A total of 45 weed species were recorded as potential weed hosts of root-knot nematodes with a gall index from 1 to 5. Using the weed and tomato bioassay method, a total of 11 nonhost 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 indicated their ability to sustain root-knot nematode populations and, thus, their potential to act as reservoir hosts.
Nomenclature: Root-knot nematodes, Meloidogyne Göldi; balsamapple, Momordica charantia L.; cutleaf groundcherry, Physalis angulata L.; ivy gourd, Coccinia grandis (L.) J. Voigt; little ironweed, Cyanthillium cinereum (L.) H. Rob.; old world diamond-flower, Oldenlandia corymbosa L.; purple bushbean, Macroptilium atropurpureum (Moc. & Sesse ex DC.) Urb.; seedbox, Ludwigia hyssopifolia (G. Don) Excell apud A. R. Fernandes; sicklepod, Senna obtusifolia (L.) H.S. Irwin & Barnaby; slender amaranth, Amaranthus viridus L.; tropic ageratum, Ageratum conyzoides L.; garden tomato, Solanum lycopersicum L.