Understanding pyrethroid susceptibility and resistance in tadpole shrimp

Jan 6, 2020

Do you want to make sure your freshly planted rice fields don't look like the muddied mess on the left below (vs. clear on right) following a pyrethroid application? Wondering if your tadpole shrimp are becoming less susceptible to pyrethroids? We do too! Pyrethroids are widely used for managing resistance, and resistance seems to be a growing issue.

We are looking for additional fields where we can sample tadpole shrimp to test for pyrethroid resistance. We will be gathering soil/shrimp and then using these samples to run laboratory bioassays and measure susceptibility. The goal is to start measuring precisely how susceptible populations are in different fields. This will help us determine precisely how resistant known resistant populations are, how prevalent low levels of resistance are, and how “susceptible” currently susceptible populations are to generate baseline data. This will help generate the long-term baseline data we need to stay on top of this issue.

We will anonymize any publicly available data. In addition, we hope that by measuring resistance in individual fields, we can help you by noting any susceptibility slippage that may not have shown up yet in terms of control. We can also help address questions about whether lack of control is due to resistance or application issues.

Types of fields:

  • Fields with known resistance to pyrethroids in tadpole shrimp (control issues).
  • Suspect fields where you think resistance is an issue, but it is a just a hunch or a concern.
  • Any other field. Even if pyrethroids have been working well, it is still good to know susceptibility levels and for us to generate baseline data.

What we need:

  • Access to field(s)
  • Summary of your ability to manage tadpole shrimp with pyrethroids, any declines in susceptibility, etc.

If you are interested, please email or call Ian Grettenberger at imgrettenberger@ucdavis.edu or (530) 752-0473.

This article was originally posted in the UC Rice Blog.

By Ian Grettenberger
Author - Assistant Specialist in CE
By Luis Espino
Author - Rice Farming Systems Advisor & Butte County Director