With the debate over the possible carcinogenity of Monsanto’s (now Bayer’s) Roundup herbicide continuing to rage, a peer-reviewed research paper partly funded by Swiss agrochemicals giant Syngenta – now owned by ChemChina – suggests that the herbicide active ingredient glyphosate would be more effective if sprayed on plants at certain times of day.

The Syngenta-supported paper, which also received funding from the UK’s Biotechnology and Biological Sciences Research Council, sidestepped questions about whether the herbicide is a health hazards and focused on the fact that plants, like people, have circadian rhythms that alter their responses to their environment.

In the research, in which the Swiss group participated together with scientists from the University of Bristol, it was determined that glyphosate was more effective at dawn, when thale cress, a popular model plant for scientists, appeared most sensitive to it. In trials, glyphosate reportedly was able to kill the germinating seedling best at that early hour, compared with dusk, when it seemed to be the least effective.

Without addressing the question of how much glyphosate could be safely used –   in the ongoing court cases brought by cancer sufferers Bayer argues that the claimants used Roundup improperly –  the researchers said that at the time of day determined most advantageous a farmer would have to spray less glyphosate to kill the same amount of weeds.

The UK scientists noted that with the market worth $5 billion in the US and $11 billion worldwide, the scale of glyphosate use makes strategies to enhance its utility commercially and environmentally attractive.

Previous studies with glyphosate have focused on its side effects on bees, aquatic animals like mollusks and crayfish as agricultural runoff pollutes nearby waterways. Weeds meanwhile have developed resistance to glyphosate, and some research connects glyphosate to a rise in antibiotic resistance, all of which gives rise to concern about the herbicide’s long-time future.

As Bayer defends itself against expensive litigation, environmental authorities thus far have declined to regulate glyphosate, due to the failure of multiple research efforts to definitively prove a link between the herbicide ingredient and cancer.

The US Environmental Protection Agency (EPA), which has completely cleared the substance of suspicion, has taken the unusual step of barring individual states such as California from requiring warning labels on Roundup packaging. An extension of the EU’s license for glyphosate will come up for a vote again next year.

But while Bayer struggles in the US, Syngenta has remained untouched by the raging debate over glyphosate. Up to now it has not faced any legal challenges concerning its herbicides in which the controversial chemical is the active ingredient, CEO Mark Patrick said last month.