Impact of Fipronil Residues on Mole Cricket Behavior and Mortality in Bermudagrass

1. NC StateUniversity Paper # 20 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

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

3. 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).

4. 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.

5. 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.

6. Materials and Methods • ‘Tifway’ bermudagrass was placed into 150 pots 19-cm in diameter on March 23, 2003. • In a greenhouse, pots were mowed and rotated twice weekly.

7. Materials and Methods • Beginning in May, fipronil was applied at 0.014 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).

8. 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.

9. 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, 2003. • Soil and plant material was divided into 0-4, 4-8, and 8-18 cm increments.

10. 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.

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

12. 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)

13. Mean Fipronil Residue Concentrations (0-4 cm)

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

15. Mole Cricket Nymph Status Combing Runs 1 and 2

16. Summary • Each treatment’s effect on mole crickets was significantly different from the nontreated. • Chi square p < 0.001 • There was no significant difference in the effectiveness of fipronil among treatments. • Fipronil may be more repellent, and its metabolites may be more lethal.

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

18. Questions?