Suppression of the Root-Knot Nematode,Meloidogyne incognita in Tomato Plants by Application of Certain Entomopathogenic Nematode Species Under Greenhouse Conditions

Abstract

The suppressive effects of six species of entomopathogenic nematodes(EPNs) against Meloidogyne incognita infected tomato were assessed in twoseparate trials under greenhouse conditions. The tested EPN species wereHeterorhabditis bacteriophora, H. megidis, H. zealandica, Steinernema feltiae, S.glaseri and S. riobravae. In the first trial, EPNs were applied as a liquid suspensionof alive or dead infective juveniles (IJs) at rate of 5000 IJs/plant in sandy and claysoils, while in the second trial, two Galleria mellonella infected cadavers of six-dayold per plant were used in sandy soil. In the two experiments, application of EPNswas accomplished simultaneously with inoculation of M. incognita. Carbofuran as astandard synthetic nematicide was used as comparison treatment at recommendedrate of 0.2 g/plant. Control treatments received only water and M. incognita at rateof1000 IJs/plant.Two months after inoculation, galling (as indicated by number of galls/plant)and reproduction (as indicated by number of egg masses /plant) as well as damage(as indicated by fresh and dry weight of areal parts) were assessed. Data showedthat, treatment of carbofuran surpassed all other treatments in minifying galling andreproduction of M. incognita in sandy and clay soils. On the other hand, curativeapplications of alive or heat-killed IJs significantly (P≤ 0.05) diminished gallformation and egg mass production in tomato roots with slightly amelioration infresh and dry weight of tomato shoot. Steinernematid species were morecomparatively effective than heterorhabditid ones. General means for number ofgalls and egg masses for steinernematid species were 52.50 and 25.33 withpercent reduction of 55.45 and 64.49 %, respectively. Whereas, the parallel valuesfor heterorhabditid species were 69.67 and 36.33 with percent reduction of 40.88and 49.07%, respectively compared to treatment of M. incognita alone. Treatmentsof alive IJs overwhelmed those of dead IJs in decreasing number of galls (withpercent reduction of 56.53 and 39.79% respectively) and egg masses (with percentreduction of 63.16 and 50.39%, successively). Moreover, utilization of two G.mellonella infected cadavers markedly lowered number of galls and egg masses and insignificantly (P≤ 0.05) improved plant growth parameters to certain extent. General means of percentage reduction in galls and egg masses were 58.46 and 54.74%, consecutively.