Field Suppression of Three White Grub Species (Coleoptera: Scarabaeidae) by the Entomogenous Nematodes Steinernema feltiae and Heterorhabditis heliothidis1

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Abstract
Laboratory and field tests were conducted from 1983 to 1985 to evaluate the effectiveness of three entomogenous nematodes in reducing white grub populations infesting grass pasture land scheduled for Christmas tree planting. Nematodes tested were three strains of Steinernema feltiae Filipjev (DD-136, Mexican, and All), Steinernema glaseri (Steiner), and Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann). The white grub complex consisted of three species: Phyllophaga anxia (LeConte), Phyllophaga fusca (Froelich), and Polyphylla comes Casey. In laboratory tests, the different nematode species demonstrated similar virulence, producing grub mortalities of 60-80% in 2-4 d. Field treatment results were highly variable; significant grub population reductions occurred at several treatment rates. Sprays with All strain caused the most consistent grub reductions. Nematodes dispersed through the soil to locate and parasitize white grubs. The highest treatment rates usually did not produce the most significant grub population reductions. Rates ranged from 0.54 to 10.76 x 105 nematodes per m2.