Japan's agriculture ministry has drafted a clean bill of health for pyraclonil, a weed-control ingredient used on rice paddies. The draft honeybee impact assessment concludes the substance is not considered likely to impair the maintenance of bee colonies, provided it is used as applied for. The ministry opened public comment on the draft on October 15, and submissions close at 23:59 on November 13, 2026.
What the draft concludes
The assessment covers 147 formulations submitted for registration, mostly granules and flowables that combine pyraclonil with other rice herbicides. They are meant for transplanted and direct-seeded paddy rice, applied to flooded fields or by unmanned aircraft, among other methods. The ingredient acts by inhibiting an enzyme (PPO) in the presence of light, which browns and dries the foliage of target weeds. As of December 2024 it was registered in the United States, South Korea, China and Thailand.
The toxicity numbers
The assessment rests on two studies on adult honeybees. Neither found a dose at which half the bees died within 48 hours, even at the highest dose tested.
| Test | 48-hour LD50 | Study year |
|---|---|---|
| Adult single contact toxicity | >100 µg ai/bee | 1997 |
| Adult single oral toxicity | >44 µg ai/bee | 2012 |
Both values exceed the 11 µg per bee level, so the draft says no precautionary label is needed. It also says pyraclonil is not an insect growth regulator. For those reasons it is not selected for risk assessment in the first round of the re-evaluation of active ingredients, and no exposure estimate was made.
Gaps in the testing record
The draft records no larval toxicity, repeated-dose oral, pollen and nectar residue, or colony-level studies. Both adult studies are unpublished, though conducted to good laboratory practice. A literature search covering October 2009 to September 2024 turned up no paper usable for the evaluation, and a call for published literature between March 20 and April 18, 2026 drew no submissions.
How the process runs
The ministry consulted its Agricultural Materials Council on May 7, 2026. The council's honeybee panel discussed the substance and approved the draft on September 10. The ministry says it will decide after considering the comments received. The comment call is voluntary, not a procedure under the Administrative Procedure Act.
Comments must be in Japanese and can be submitted through the e-Gov form or by post to the ministry's agricultural chemicals office. Phone comments are not accepted, and the ministry will not reply to individual submissions.