Wednesday, December 13, 2006 - 2:59 PM

Effects of fast host desiccation treatments on infective juvenile production and tolerance to osmotic stress of two entomopathogenic nematodes

Jaime Ruiz-Vega, jruizv@yahoo.com1, Edwin E. Lewis, eelewis@ucdavis.edu2, Glen Stevens, gnstevens@ucdavis.edu2, Hanayo Arimoto, guppy.30@gmail.com2, and Harry K. Kaya, hkkaya@ucdavis.edu2. (1) Instituto Politecnico Nacional, CIIDIR Oaxaca, Calle Hornos 1003, Fracc. Indeco Xoxo, 71230 Santa Cruz, Xoxocotlán, Oaxaca, Mexico, (2) University of California - Davis, Department of Nematology, One Shields Ave, Davis, CA

Entomopathogenic nematodes (EPN) such as Steinernema glaseri and Heterorhabditis bacteriophora are being used commercially in several countries for the control of soil dwelling pests. However, their effectiveness is affected by environmental stresses such as low soil moisture and high temperatures. A novel approach is to use the cadavers of Galleria mellonella as carriers of the nematodes. It has been reported that the IJ's emerging from cadavers have increased infectivity and higher tolerance to low soil moisture and high temperatures. The purpose of this research was to determine the optimum time post infection and intensity of desiccation for higher IJ's production and their effects on osmotic stress tolerance in these EPN. Our results showed that timing (2, 4 and 6 days post-infection) and intensity (1, 2 and 4 days in a desiccator) affected weight reduction, especially in S. glaseri, which resulted in higher death rates of the IJ's. The total number of nematodes, however, was not related to the opportunity or intensity of the stress treatments, but to nematode species and initial weight of the hosts. Also, the initial weight was not related to percentage of dead IJ's produced. In an evaluation of survivorship in a 30 % PEG8000 solution (T=23.5 °C), no differences in tolerance among different stress treatments were detected, but S. glaseri showed a significantly higher tolerance than H. bacteriophora.

Species 1: Rhabditida Steinernematidae Steinernema glaseri
Species 2: Rhabditida Heterorhabditidae Heterorhabditis bacteriophora

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