Host status of woody ornamental plants native to southeastern U.S.A. to three Meloidogyne species

Use of indigenous (native) plants in landscapes is of interest because of their perceived low maintenance requirements, and possible resistance to pests including plant-parasitic nematodes. Meloidogyne spp. (root-knot nematodes) damage many ornamental landscape plants in the southeastern U.S.A. Infected plants may be stunted and can lose aesthetic value due to chlorosis, wilting, and leaf margin necrosis. We assessed reproduction of three root-knot nematode species, Meloidogyne arenaria, M. incognita, and M. javanica, on five plant taxa native to the southeastern U.S.A. and three non-native species commonly used in landscapes. The native taxa were: Hydrangea quercifolia 'Oakleaf,' Viburnum obovatum 'Densa,' Itea virginica 'Little Henry,' Illicium parviflorum, and Clethra alnifolia 'Ruby Spice.' The non-native shrubs were: Ligustrum japonicum 'Texanum,' Ilex crenata 'Compacta,' and Buxus microphylla 'Wintergem.' An interaction between plant taxa and Meloidogyne species was observed (P < 0.0001), and galling and nematode eggs were abundant on roots of the three non-native taxa. Among the plant species tested, highest galling (10) was observed on roots of I. crenata 'Compacta' infected with M. incognita, but largest number of eggs (6,397 eggs/g of roots) was observed in plants of this cultivar inoculated with M. javanica. Few or no galls were observed on roots of the five native plant taxa, and nematode eggs were recovered only from roots of I. virginica 'Little Henry' inoculated with M. arenaria and M. javanica (13 and 20 eggs/g of roots, respectively). Weight of shoots or roots of all species was not affected by nematode inoculation. Due to lack of root gall development and little or no reproduction on the native taxa, we conclude that these are poor or non-hosts to the three species of Meloidogyne. Landscape plantings of these plants, therefore, should be recommended as alternatives in sites with soil infested by Meloidogyne arenaria, M. incognita, or M. javanica.