Question of the Week
Answer: Because tadpole shrimp do not hatch from eggs until exposed to water, rice that is grown in dry-seeded systems and not flooded until rice is at the 4–5 leaf stage should be safe from tadpole shrimp injury. This practice promotes large plants with adequate root systems when the field is flooded. However, heavy rainfall or flooding shortly after seeding can cause drill seeded rice to mimic a water-seeded rice production system if the field is not able to be drained; this situation can lead to tadpole shrimp damaging rice in a dry-seeded system.
The number one control option for tadpole shrimp is to avoid water-seeding rice and to flood a field after the rice has an established root system. However, in fields that are water-seeded, the field should be seeded as soon as possible after the flood is established because tadpole shrimp hatch once a field is flooded. This will minimize the amount of time that tadpole shrimp grow and maximize the growth of rice plants while tadpole shrimp are still small. The idea is that the rice will grow out of the vulnerable stage before tadpole shrimp can damage the rice.
Draining a field can be useful in killing tadpole shrimp, but rainfall can prevent this from being effective. However, greater input costs (i.e., additional applications of herbicide, fertilizer, or both; pumping costs; and other expenses) are associated with draining.
Here are to resources on this topic that you should find useful:
Shrimp Pest Control in Sight
California Agricultural Technology Institute
UC Pest Management Guidelines: Tadpole Shrimp
University of California Agriculture & Natural Resources
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