Having a weed-free rice field is ideal, but not at the expense of nature. IRRI, through the Closing Rice Yield Gaps in Asia with Reduced Environmental Footprints (CORIGAP) project, continues to do cutting-edge research to boost rice productivity while safeguarding environmental health.
According to Molly Shuman-Goodier, a CORIGAP-supported PhD student from the Northern Arizona University, amphibians species, such as frogs, contribute a number of beneficial ecosystem services to wetlands and irrigated rice fields. However, the application of herbicides like butchalor, which is used extensively in rice fields in Southeast Asia, affect the amphibians’ reproductive and developmental cycles.
“We would like to find out whether the application of the herbicide affect the growth and thyroid physiology of the cane toads, at what stage it is mostly affected, and to test the degree to which tadpoles can acclimatize to sub-lethal herbicide exposure,” Molly says.
The key findings support recent work indicating that the rice herbicide butachlor causes thyroid endocrine disruption in vertebrates. This means that wildlife and human health are at stake when exposed to this herbicide in the rice fields. “Because the cane toad is a widespread invasive species and abundant within rice fields in the Philippines and in other tropical countries where it has been introduced, it can serve as an indicator to assess consequences of pesticide exposure,” Molly adds.
Building on these findings, the first of which were published in Ecotoxicology in late 2017, Molly identifies more exciting research areas. “By using cane toad larvae, we can assess whether other pesticide products used in rice negatively affect development at concentrations observed in the environment,” she said. Further research can be done to understand the diet of rice field amphibians, and to help understand whether native frogs, such as the Luzon wart frog, consume rice pests. This can help answer the question whether the presence of frogs may reduce the need for insecticide application.
Last November, Molly’s research on amphibians was awarded the best PhD platform presentation during the Spotlight Session at the globally renowned Society of Environmental Toxicology and Chemistry (SETAC) in Sacramento, California, USA. A chapter of her doctoral dissertation titled “Invasive cane toads: Good for something? Developmental assays reveal safety concerns of the common rice herbicide, butachlor” was chosen among the 256 PhD student presenters.