Nematodos entomopatogenos y hongos del suelo con potencial antagonico a nematodos entomopatogenos asociados a citricas

The use of entomopathogenic nematodes (EPN) to control insect pests in the soil is a common practice. The objectives of this investigation were to characterize the communities of EPN associated with citrus cultivation, identify the species of fungi with antagonistic potential against soil nematodes associated with citrus, and evaluate the susceptibility of Diaprepes abbreviatus to native Rhabditis spp. nematodes and the introduced EPNs Steinernema glaseri (NJ93 isolate) and Heterorhabditis bacteriophora. Samples were collected twice from five citrus orchards at the Agricultural Experiment Stations in Isabela and Adjuntas. The first was conducted from September to November 2007 and the second from April to May 2008. Nematode extraction was performed using Galleria mellonella larvae. Fungi isolation from the soil was achieved by performing serial dilutions up to 10-3. A one ml aliquot of the dilution was then placed on Rose Bengal Streptomyacin Agar. The fungal colonies were counted and expressed as log10 ufc/g of dry soil. To evaluate the susceptibility of D. abbreviatus to the EPNs and to the Rhabditis spp., D. abbreviatus larvae were inoculated with 10 IJ/cm2 of soil of each nematode species in sterile soil. For the combined treatments half of the dose was used; water was used for control. Mortality was evaluated at 2, 5 and 10 days. In none of the sampled soils were EPNs observed, but nematodes in the genus Rhabdita were consistently isolated from cadavers that had been exposed to collected soil samples. The fungi most frequently isolated and identified were: Aspergillus niger, Chaetomium globosum, Fusarium solani, Fusarium oxiporum, Gliocladium catenulatum, Paecilomyces spp., Penicillium spp., Trichoderma viride and Verticillium spp. There was no interaction between Rhabditis spp. and the EPNs. H. bacteriophora and S. glaseri (NJ93 isolate). H. bacteriophora showed the greatest efficacy in the control of D. abbreviatus.