Developing integrated pest management practices for tadpole shrimp (Triops longicaudatus) in California rice fields

ABSTRACT: Tadpole shrimp (Triops longicaudatus; TPS) is a vernal pool crustacean, native to the western hemisphere. Historically, population levels were tolerable and seldom caused economic damage in rice. However over the past decade TPS has increasingly become a significant pest for California rice growers. TPS feeds on and uproots young seedlings; its swimming and burrowing habits increase the suspended silt in the flooded fields and disrupt the photosynthetic capacity of the young rice seedlings. TPS eggs can remain dormant for ~20 years or more (Brendonck and Meester, 2003). This evolutionary adaption could be key to the recent population explosion of TPS in California rice.  By characterizing the spatial distribution of TPS eggs (eggs in diapause vs active eggs) through sampling farmers’ fields and analyzing TPS egg frequencies using geostatistical technique kriging, we can develop effective monitoring techniques. This would reduce unnecessary pre-flood insecticide applications. Eggs recovered from farmers’ fields will be photographed using novel hyperspectral imaging to distinguish between diapause and active eggs, and to quantify this ratio across the sample points in each field. We can subsequently quantify changes in this ratio under various treatments, such as resource availability, temperature, and dissolved oxygen throughout the adults’ lifespan. This research will provide insight into TPS’ recent transition from an occasional to a significantly chronic pest.