Evaluation of Weed Species for Host Status to the Root-Knot Nematodes Meloidogyne enterolobii and M. incognita Race 4

Weeds that compete with valuable crops can also host plant-parasitic nematodes, acting as a source of nematode inoculum in a field and further damaging crops. The host status of 10 weed species commonly found in North Carolina, USA, was determined for the root-knot nematodes Meloidogyne enterolobii and M. incognita race 4 in the greenhouse. Each weed species was challenged with 5,000 eggs/plant of either M. enterolobii or M. incognita race 4, with five replicate plants per treatment in two separate greenhouse trials. Root galling severity and total number of nematode eggs per root system were recorded 60 days after inoculation. Reproduction factor (Rf = final nematode population/initial nematode population) was calculated to determine the host status of each weed species to M. enterolobii and M. incognita race 4. Four weed species (Datura stramonium, Digitaria sanguinalis, Senna obtusifolia, and Cyperus esculentus) were poor hosts (Rf < 1) to both nematode species, and roots of these weed plants did not display galling. Four weed species (Ipomoea hederacea, Amaranthus palmeri, Portulaca pilosa, and Ipomoea lacunosa) were hosts (Rf > 1) to both nematode species, and all had observable root gall formation. Sida rhombifolia and Cyperus rotundus were poor hosts to M. enterolobii but susceptible hosts to M. incognita. This study documents a differential host status of some common weeds to M. enterolobii and M. incognita race 4, and these results highlight the necessity of managing root-knot nematodes through controlling weeds in order to protect valuable crops.