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Abstract

Cucumber (Cucumis sativus) cultivation in commercial greenhouses occupies an important section of vegetable production in Iran. Root-knot nematodeMeloidogyne javanicaconsidered the most destructive soil-borne pathogen in cucumber growing greenhouses. In this study, biocontrol activity of three species of entomopathogenic nematodes (EPNs, i.e.,Steinernema carpocapsae,S. feltiaeandHeterorhabditis bacteriophora) was determined onM. javanicainfecting cucumber under growth chamber and greenhouse conditions. The aqueous suspension of infective juveniles (IJs) was used in five different inoculation times (i.e., 1 or 2 weeks pre-inoculation, simultaneously, and 1 or 2 weeks post-inoculation of the pathogenic nematode into the cucumber soil). Results showed thatS. carpocapsaeandH. bacteriophorawere capable of decreasing all the pathogenicity indices (number of galls, eggs and egg masses) ofM. javanicain growth chamber, as well as greenhouse conditions. The best application time for EPNs was determined as 1 week after post-inoculation ofM. javanicainto the soil. Although EPNs showed significant inhibition in 25 IJ/cm(2)(3.8 IJ/cm(3)) of soil, the best biocontrol activity was observed in 125 IJ/cm(2)(19.1 IJ/cm(3)). Furthermore, the highest reduction in pathogenicity indices was observed when EPNs-colonized cadavers were used as carrier of biocontrol agents. Significant increase in plant growth indices (e.g., fresh/dry weight of shoots/roots) was recorded for all treatments exceptS. feltiae. Altogether, our results provide a novel insight into the applicability of EPNs against the root-knot nematodeM. javanicaon cucumber. Further investigations are warranted to evaluate the commercial usability of the agents in cucumber growing greenhouses in Iran.