have been used as inundative release to control several foliar insect pests in greenhouse. In this study infectivity potential of two species of entomopathogenic nematodes include Steinernema feltiae and Heterorhabditis bacteriophora as a biological control agent in different concentrations (25, 50, 100, 150, 200, 250 infective juvenile per cm2 ) along with Triton XIOO (%011 v/v) were studied on second instar nymphs of T. vaporariorum on two host plants (cucumber and pepper) in laboratory and greenhouse condition. H. bacteriophora had the lowest LC50 value with 83 IJs cm·1 against second nymph stage ofT. vaporariorum and LC50 for S. feltiae was 93 IJs cm·1 of leaf area. S. f eltiae showed the lowest LC50 value, equals to 143 IJs cm-1 against adult insects ofT. vaporariorum while this value for H. bacteriophora was 198 IJs cm-1 of leaf area in laboratory condition. The mortality of second nymph stage increased by increasing the IJs concentration from 25 to 250 IJs in greenhouse condition. The highest mortality rate of the second nymph instars of whitefly were obtained from the application of S. feltiae with concentration of 250 IJs cm-1 on cucumber (%49 ± SE). The lower mortality was reached from the application of H. bacteriophora with concentration of 25 IJs cm-1 on pepper (%3.39 ± SE). The mean mortality by each EPN species at all IJs rates was signjficantly higher on cucumber than on pepper.The application of S. feltiae against the second The greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), is an important polyphagous pest of various crops as well a major concern in greenhouse. Entomopathogenic nematodes in the families Steinemematidae and Heterorhabditidae can penetrate and cause death of many economically important pests and can effective biological alternatives to chemical pesticides. Some entomopathogenic nematodes species instar nymph on both host plants resulted significant mortality of the pest compared to H. bacteriophora. The current work showed that both species of nematodes S. feltiae and H. bacteriophora could be suitable as a tool in the greenhouse management in greenhouse, but furture studies is required.

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