Researchers are evaluating alternative methods for addressing tadpole shrimp in rice fields. Shrimp can be particularly problematic during the seedling stage when they feed on germinating seeds. The pest creates a host of issues for growers by affecting yield, weed pressures, and fertilizer efficiency.
“If they go unnoticed, they can wipe you out. A grower might have to reseed a field which is never very successful,” said Luis Espino, UC Cooperative Extension Rice Farm Advisor. “Most of the time, once they get you one year, the next year the grower is ready for them.”
Tadpole shrimp are an abnormal pest. Eggs remain in the soil and are be a predictable occurrence once water is added to the field. Pyrethroids are the primary insecticides used for management. Researchers are looking for viable alternatives to a reliance on pyrethroids.
“Historically that’s worked, but we’re putting a lot of pressure resistance-wise on these materials,” said Ian Grettenberger, Assistant Cooperative Extension Specialist at UC Davis. “Growers already know that they have resistance in some areas in terms of field efficacy and field failures in some fairly isolated instances thus far.”
Researchers are working with a variety of materials in their insecticide trials. The work also includes some alternative methods such as mosquitofish and an oil-based product used to combat mosquitos. Different application rates and timing strategies are also being evaluated for their efficacy against tadpole shrimp. “The idea would be if we could use a lower rate for some of these insecticides then it would make it more competitive with the currently used pyrethroids which are rather cheap in general,” said Grettenberger.
Pyrethroids have proven to be an important tool for growers with tadpole shrimp issues. Research into other methods for combatting the pest not only addresses resistance concerns but alternatives could prove immensely valuable in the future. As more attention is paid to water quality and pyrethroid residues it is important to have other viable options available.