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Project description

Synergism of Imidacloprid and Entomopathogenic Nematodes: a Novel Approach to White Grub Control in Turfgrass. (97BU013)
Program UC IPM competitive research grants program
H.K. Kaya, Nematology, UC Davis
A.M. Koppenhofer, Nematology, UC Davis
Host/habitat Turfgrass
Pest Masked Chafer Cyclocephala hirta; Japanese Beetle Popillia japonica
Discipline Entomology
Entopathogenic nematodes; Steinernema kushidi
Biorational Use of Biotic Agents or Chemicals
Start year (duration)  1997 (Three Years)
Objectives Test the feasibility of combinations of the chloronicotinyl insecticide, imidacloprid (IMI), and entomopathgenic nematodes (EN), with emphasis on the scarab-specific Steinernema kushidi,, and Japanese beetle (Popillia japonica); (2) the direct effect of IMI on EN infective juveniles; (3) the effect of IMI on EN recycling in white grub hosts; and (4) the pathogenicity of S. kushidai and its capacity to recycle in various life stages of the scarab pests.
We observed a synergistic effect of combinations of the synthetic insecticide imidacloprid and entomopathogenic nematodes on mortality of 3rd instar grubs of the masked chafers, Cyclocephala hirta and C. pasadenae, and the Japanese beetle, P. japonica. In greenhouse and field experiments, this synergism occurred whether imidacloprid and nematodes were applied simultaneously or nematode application was delayed by 14 d. Nematode species had a significant effect on the interaction. Thus, the most consistent synergism occurred between Steinernema glaseri and imidacloprid but the interaction between Heterorhabditis bacteriophora and imidacloprid, although weaker, was also synergistic. Steinernema kushidai, on the other hand, did not interact with imidacloprid.

Laboratory experiments showed that entomopathogenic nematodes are compatible with imidacloprid in tank mixes with no effect on nematode survival and only limited negative effects on nematode infectivity, i.e., only for some nematode species and only at very high imidacloprid concentrations. Similarly, the concomitant application of imidacloprid had only limited negative effects on the recycling of nematodes in infected white grubs, i.e., nematode progeny was somewhat reduced for some nematode species at the highest imidacloprid application rates. This effect, however, was compensated for by the higher number of grubs succumbing to nematode infection in the presence of imidacloprid.

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