Managing Tadpole Shrimp in Rice Fields

Tim Hammerich

News Reporter

Rice is such a unique crop, and with a unique crop you’re going to get unique pests. Some California rice producers are noticing tadpole shrimp are showing signs of resistance to the pyrethroids that have managed the pest in the past. Ian Grettenberger is an assistant cooperative extension specialist with UC Ag and Natural Resources.

Grettenberger… “Tadpole shrimp are a funny critter. They're adapted to Vernal pools, evolutionarily. And so they are an organism where you add water and eggs hatch, basically. And so their eggs are actually in the soil. They're desiccated, dry. Once water is added and the temperature is to a certain level, then they hatch. And that corresponds with when fields are flooded with rice, and then they start growing.”

Grettenberger says these shrimp have evolved to mature at just the right time to feed on rice seedlings.

Grettenberger… “Water is added to the fields and then they seed somewhere thereafter. And when they're little, they're just feeding on algae, phytoplankton, tiny little things. They can't do anything to a rice plant. But then once they get to a certain size, then they can start to actually feed on the rice at that point. And so that's when the damage occurs.”

Grettenberger and others are doing research to quantify resistance levels, and explore alternatives for managing this pest.