Compatibility of Steinernema feltiae (Nematoda: Steinernematidae) with Pesticides and Plant Growth Regulators Used in Glasshouse Plant Production

Abstract

Compatibility of the entomopathogenic nematode, Steinernema feltiae Filipjev with 17 different pesticides and three plant growth regulators, recommended for drench application in glasshouses, was evaluated. The products tested were two biofungicides, Streptomyces griseoviridis (Mycostop) and Trichoderma harzianum (Rootshield), nine chemical fungicides, iprodione (Chipco 26GT), thiophanate-methyl (Fungo Flo 4.5F), azoxystrobin (Heritage), fludioxonil (Medallion), flutolanil (Prostar), mefenoxam (SudDue Maxx 21.3ME), PCNB (Terraclor 400F), triflumizole (Terraguard), and etridiazole (Terrazole), two bioinsecticides, spinosad (Conserve SC) and Bacillus thuringiensis subsp. israelensis (Gnatrol), three chemical insecticides diflubenzuron (Adept IGR), acephate (Orthene), and fenoxycarb (Precision 25WP), one herbicide, clethodim (Envoy) and three plant growth regulators, ancymidol (A-Rest), paclobutrazol (Bonzi), and uniconazole-P (Sumagic). Infective juvenile nematodes were exposed to each product at the highest recommended concentration in 24-well plates at 22°C. Observations on the viability and infectivity of the nematodes were made at 4, 24, and 72 h after exposure. We found that S. feltiae is compatible with the majority of the tested formulations with no loss in viability and infectivity up to 24 h of exposure. The viability of S. feltiae was more than 80% in all the products even after 72 h of exposure. Three pesticide formulations, Prostar (1%), Gnatrol (9%), and Terrazole (10%) decreased the viability of S. feltiae significantly within 24 h compared to the controls. However, during the 24 to 72 hr incubation period, eight pesticides affected the viability of S. feltiae with Gnatrol and Terrazole causing the highest decrease (17% and 15%, respectively). Only Terrazole decreased the infectivity of S. feltiae to Galleria mellonella larvae compared to the control when tested after 24 h exposure. At 72 hr, Orthene and Terrazole caused significant decrease in the infectivity of S. feltiae (10% and 15%, respectively) and Gnatrol caused a significant increase in the infectivity (11%) compared to the control. Our results suggest that S. feltiae can be tank-mixed and applied in combination with all the tested formulations, except Terrazole.

Keywords:

• IPM
• insect parasitic nematodes
• insecticides
• fungicides
• herbicides
• tank mixing
• safety
• side effect nontarget effects
• beneficial organisms

Acknowledgments

We thank Mr. Kevin Power, Dr. Sukhbir K. Grewal, and Dr. Douglas R. Richmond for technical assistance during the experiments. We also thank all the corporations for providing samples of the formulations tested. Special appreciation to the Brazilian Agricultural Corporation, EMBRAPA, for providing paid leave to E.A.B. De Nardo to participate in this study. This work was supported by the USDA-PMAP grant number 00-34381-9556 to P.S.Grewal.