Impact of Fipronil Residues on Mole Cricket Behavior and Mortality in Bermudagrass H.D. Cummings*, R.L. Brandenburg, R.B. Leidy, F.H. Yelverton, and J.B. Weber NCSU, Raleigh, NC NC State University Paper # 20

Mole cricket tunneling and feeding is injurious to turf.Mole cricket tunneling and feeding is injurious to turf.

Introduction Mole crickets can be a devastating pest due to the injury to the turf and high cost of control and turf recovery (Frank & Parkman 1999). Mole crickets spend most of their lives tunneling through soil to feed on roots and soil organisms and uproot turf plants which dry out and die (Leslie 1994).

Introduction Fipronil and/or its metabolites effectively control mole crickets, home pests, termites, fire ants, water rice weevil, and field corn pest (USGS 2003). Fipronil has four major metabolites: –Fipronil sulfone - oxidation in soil. –Fipronil sulfide - anaerobic metabolism. –Desulfinylfipronil - photodegradation in water and on soil. –Fipronil amide - alkaline hydrolysis in water and soil.

Objectives To determine the length of influence of fipronil and/or its metabolites on tawny mole cricket nymphs in bermudagrass. To measure degradation of fipronil and appearance of fipronil metabolites yielding the various levels of nymph responses.

Materials and Methods ‘Tifway’ bermudagrass was placed into 150 pots 19-cm in diameter on March 23, In a greenhouse, pots were mowed and rotated twice weekly.

Materials and Methods Beginning in May, fipronil was applied at g ai/ha 120, 90, 60, 30, and 0 days before adding one tawny mole cricket nymph (Scapteriscus vicinus) to each pot (11 reps x 2 runs spaced two weeks apart).

Materials and Methods  Mole cricket nymphs were collected on Aug. 14 from Oyster Bay Golf links and Sept. 2, 2003 from Sea Trails Golf links on the coast of NC.  The mole cricket nymphs were kept in individual containers and fed worms.

Materials and Methods One mole crickets was added to each pot on Sept. 5 and Sept. 19, 2003 for Runs-1 and -2 respectively. Pots were harvested on Sept. 15 and Sept. 23, Soil and plant material was divided into 0-4, 4-8, and cm increments.

Materials and Methods Status of nymphs was recorded was Alive, Dead, or Absent. Nymphs served as sentinels of fipronil or its metabolites. Depth of nymphs was noted. Run-1 had 11 not treated replicates, and Run-2 had 26 not treated replicates.

Materials and Methods Sonication removes adsorbed compounds from soil (10 g soil) Rotoevaporator concentrates extract

Materials and Methods Fipronil and fipronil metabolite concentrations in the soil in the 0-4 increment were determined for 4 reps in each treatment. Gas chromatograph (GC) separates the compounds and determines the concentration of the compound of interest (GC/Mass Spec with ECD detector)

Mean Fipronil Residue Concentrations (0-4 cm)

Mean Fipronil, Fipronil Sulfide, and Fipronil Sulfone Residue Concentrations (0-4 cm)

Mole Cricket Nymph Status Combing Runs 1 and 2 Fipronil Application Time Alive (%) Dead (%) Absent (%) 0 Day Day Day Day Day Not Treated

Mole Cricket Nymph Status Combing Runs 1 and 2 Frequency Row % Col % AliveDeadAbsentTotal Frequency Row % Col % AliveDeadAbsentTotal 0 Day Day Day Day Day Not Treated Total

Summary Each treatment’s effect on mole crickets was significantly different from the nontreated. –Chi square p < There was no significant difference in the effectiveness of fipronil among treatments. Fipronil may be more repellent, and its metabolites may be more lethal.

Final Conclusions Fipronil can provide season-long control (120 day) by causing mortality or avoidance behavior.

Questions?Questions?