Effect of Nematode and Fungal Treatments on Nontarget Turfgrass-Inhabiting Arthropod and Nematode Populations

Abstract

Arthropod and nematode population densities in 'Tifway' bermudagrass were studied in field plots to determine the impact of long-term treatments with an organophosphate insecticide (chlorpyrifos), entomopathogenic nematodes (Heterorhabditis bacteriophora Poinar (Heterorhab- ditidae), Steinernema carpocapsae (Weiser), S. riobravis (Cabanilas, Poinar & Raulston) (Stein- ernematidae)), and an entomopathogenic fungus (Beauveria bassiana (Balsamo) Vuillemin (Deu- teromycotina: Hypomycetes)) applied alone and in combinations. Fifty-five arthropod families or suborders were recorded during a 2-yr period. Staphylinidae, Sminthuridae, Isotomidae, and Ori- batida were the four most abundant species groups, accounting for 97.0% of the arthropods collected. Three orders of nematodes and a miscellaneous nematode category also were encountered. Ty- lenchida was the most abundant nematode species group, accounting for 77.2% of the nematodes collected. Populations of Lycosidae and Staphylinidae were not significantly different from the control in any treatment. However, chlorpyrifos reduced Lycosidae counts in comparison to H. bacteriophora, S. carpocapsae, and H. bacteriophora 1 B. bassiana. Chlorpyrifos also lowered Staphylinidae counts in comparison to B. bassiana, S. carpocapsae, and S. riobravis. Miscellaneous Araneae, Formicidae, and Scelionidae were less abundant in the chlorpyrifos treated plots than they were in any others. By contrast, Sminthuridae densities were highest in the chlorpyrifos plots and were unaffected by any other treatment. In general, chlorpyrifos diminished the abundances of each of the following categories of arthropods compared with all other treatments: plant-inhabiting predators 1 parasitoids, soil herbivores, thatch detritivores, and soil predators. By comparison, soil detritivores were as common in the chlorpyrifos treatment as they were in the B. bassiana, S. carpocapsae, H. bacteriophora 1 B. bassiana, and S. riobravis 1 B. bassiana treatments and were more abundant there than in the H. bacteriophora, S. riobravis, S carpocapsae 1 B. bassiana, and untreated control treatments. In general, fungus 1 nematode treatments showed no evidence of synergism and chlorpyrifos had a stronger negative impact on nontarget arthropod densities than did the microbial treatments.