NOTES ON TAXONOMY AND BIOLOGY: Female M. exigua have a roughly rounded cuticular perineal pattern with flattened dorsal arch and widely spaced coarse striae. This root-knot nematode has sedentary endoparasitic habits. Second-stage juveniles (J2) in the soil penetrate host roots where they establish a specialized feeding site (giant cells) in the stele. As J2 develop, they cause small and rounded apical root swellings and become swollen females. Gravid females produce egg masses protruding from the root surface (Cain, 1974; Lehman and Lordello 1982).
GEOGRAPHICAL DISTRIBUTION: This species has a wide geographical distribution. It has been reported in Bolivia, Brazil, Colombia, Costa Rica, Dominican Republic, El Salvador, French Guiana, French West Indies, Guatemala, Honduras, India, Peru, Suriname, Trinidad and Tobago, and Venezuela.
HOSTS: Amaranthus (Amaranthus deflexus), banana (Musa sp.), black nightshade (Solanum nigrum), blue dawn flower (Ipomea acuminata and I. aristolochiaefolia) coffee (Coffea arabica, C. eugenoides, and Coffea sp.), Commelina diffusa, cucumber (Cucumis sativus), dundellion (Taracaxum sp.), Hydrocotyle sp., Inga sp., Leonorus sibiricus, nutsedge (Cyperus rotundus), onion (Allium cepa), pepper (Capsicum annuuum), Pilea sp. rice (Oryza sativa), Spanish needle (Bidens pilosa), sourge (Euphorbia heterophylla), stagger weed (Stachys arvensis), sugarcane (Saccharum officinarum), tomato (Lycopersicon esculentum), tree tomato (Cyphomandra betacea), and watermelon (Citrullus lanatus). Reports of nematode infection on citrus and citrus relatives have not been confirmed.
CROP LOSSES: Decline and dieback of coffee trees and yield suppression up to 50% are associated with nematode infection in Brazil and South America (Campos et al., 1990; Lehman and Lordello, 1982)
MEANS OF MOVEMENT AND DISPERSAL: Through root material, soil debris and poorly sanitized bare root propagative plant material.
RATING: (M) Due to this nematode's wide host range and distribution, it was given a moderate priority rating.
CAB International. 2001. Meloidogyne exigua in Crop protection compendium, global module, 3rd editon.
Cain, S. C. 1974. Meloidogyne exigua. CIH description of plant parasitic nematodes Set 4, No. 49. St. Albans, UK: Commonwealth Institute of Helminthology.
Campos, V, P. Sivapalan, and N. C. Gnanapragasam. 1990. Nematode parasites of coffee, cocoa, and tea. Pp. 387-430 in M. Luc, R. A. Sikora, and J. Bridge eds. Plant parasitic nematodes in tropical and subtropical agriculture. Wallingford, UK: CAB International.
Lehman, P. S., and L. G. E. Lordello. 1982. Meloidogyne exigua, a root-knot nematode of coffee. Nematology Circular No. 88, pp.4. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, FL, USA.