Impacts of the herbicide butachlor on the larvae of a paddy field breeding frog (Fejervarya limnocharis) in subtropical Taiwan

Abstract

Butachlor is the most commonly used herbicide on paddy fields in Taiwan and throughout Southeast Asia. Since paddy fields provide habitat for pond breeding amphibians, we examined growth, development, time to metamorphosis, and survival of alpine cricket frog tadpoles (Fejervarya limnocharis) exposed to environmentally realistic concentrations of butachlor. We documented negative impacts of butachlor on survival, development, and time to metamorphosis, but not on tadpole growth. The 96 h LC(50) for tadpoles was 0.87 mg/l, much lower than the 4.8 mg/l recommended dosage for application to paddy fields. Even given the rapid breakdown of butachlor, tadpoles would be exposed to concentrations in excess of their 96 h LC(50) for an estimated 126 h. We also documented DNA damage (genotoxicity) in tadpoles exposed to butachlor at concentrations an order of magnitude less than the 4.8 mg/l recommended application rate. We did not find that butachlor depressed cholinesterase activity of tadpoles, unlike most organophosphorus insecticides. We conclude that butachlor is likely to have widespread negative impacts on amphibians occupying paddy fields with traditional herbicide application.

Toxicity of Herbicides: Impact on Aquatic and Soil Biota and Human Health

“…The authors observed that the three herbicides, particularly thiobencarb, are toxic for tadpoles (LD50 test), even for concentrations found in waters where the rice is cultivated. In a similar study carried out by Liu et al [43], it was observed that the effect of the herbicide butachlor (most used herbicide in rice planting in Taiwan and Southeast Asia) on the organism Fejervarya limnocharis (alpine cricket frog) exposed to concentrations used in the field. In this study no effect on the growth of tadpoles of F. limnocharis was observed, but there was a negative action on survival, development and time of metamorphosis.…”

Detecting genomic damages in the frog Dendropsophus minutus: preserved versus perturbed areas

“…Although we could not measure the amount of pesticides and heavy metals, according to the local residents, those areas are well known for the use of agrochemicals, so the greater extent of DNA damage in the animals collected from perturbed areas can be explained by their characteristics, such as the presence of agrochemicals. Several authors have reported that chronic and/or acute exposure to heavy metals, herbicides, and pesticides can result in a variety of genotoxic, mutagenic, teratogenetic, and reproductive anomalies in amphibians (Campana et al 2003;Unrine et al 2007;Yin et al 2008;Peltzer et al 2008;Liu et al 2011;Nikoloff et al 2014). However, due to the complex mix of substances in agroecosystems, which could not be measured, it is difficult to link the genotoxic effects to a specific agent or element (Govindarajulu 2008).…”

Integrated pest management for sustainable rice cultivation: a holistic approach

“…Herbicides can be detrimental to wildlife (Takamura and Yasuno, 1986;Saka, 2010;Liu et al, 2011). Herbicide residues can also kill native vegetation and reduce the yields of successive grain crops, pastures or vegetable crops such that the use of selective herbicides prohibits certain crop rotations (Sudianto et al, 2013).…”