Herbicide resistant wild oats in spotlight

Growers may have believed they were using good weed control strategies but, through continued use of Group A fop' herbicides, they unfortunately have encouraged the emergence of this resistance problem.

Outbreaks of herbicide-resistant wild oats in northern NSW are targeted in a new research effort supported by growers through the Grains Research and Development Corporation (GRDC).

The first case of resistance — to the Group A herbicides known as 'fops' — was confirmed last June after being reported in a paddock at Croppa Creek, in northern NSW, by Moree agronomist Chris Cole.

It brought warnings from weeds scientists that the identified outbreak almost certainly would not be the only one in the northern grains region.

NSW Agriculture agronomist Warwick Felton said surveys since had identified several other paddocks at Croppa Creek and North Star with similar resistance problems.

Emergency support from growers through the GRDC has allowed "an expansion of research work at the University of Queensland and the Queensland Wheat Research Institute (QWRI), control and management of the outbreaks we know about, and a major communications effort by farming systems extension specialist Jan

Growers may have believed they were using good weed control strategies but, through continued use of Group A fop' herbicides, they unfortunately have encouraged the emergence of this resistance problem.

Outbreaks of herbicide-resistant wild oats in northern NSW are targeted in a new research effort supported by growers through the Grains Research and Development Corporation (GRDC).

The first case of resistance — to the Group A herbicides known as 'fops' — was confirmed last June after being reported in a paddock at Croppa Creek, in northern NSW, by Moree agronomist Chris Cole.

It brought warnings from weeds scientists that the identified outbreak almost certainly would not be the only one in the northern grains region.

NSW Agriculture agronomist Warwick Felton said surveys since had identified several other paddocks at Croppa Creek and North Star with similar resistance problems.

Emergency support from growers through the GRDC has allowed "an expansion of research work at the University of Queensland and the Queensland Wheat Research Institute (QWRI), control and management of the outbreaks we know about, and a major communications effort by farming systems extension specialist Jan Edwards to educate graingrowers about herbicide resistance," said Mr Felton.

Move out of winter cropping

Mr Felton said the first step for the owners of the paddocks containing resistant wild oats would be to move out of winter cropping.

They should continue fallowing through to sorghum in the summer of 1998 — spraying with chemicals from other groups that still gave effective control of wild oats.

"While it is still a possibility, we believe the probability of wild oat resistance being found in Queensland is less because more growers there continue to rotate sorghum with their winter crops," Mr Felton said.

"In northern NSW there has been a widespread trend away from sorghum — to continual winter cropping with cereals and pulses — coinciding with a move away from residual weedicides to post-emergent sprays.

"Growers may have believed they were using good weed control strategies but, through continued use of Group A 'fop' herbicides, they unfortunately have encouraged the emergence of this resistance problem."

Mr Felton said contaminated seed has also played a role. After examining wild oat seed from the first reported outbreak, University of Queensland research scientist Don Wills said besides strong resistance to a number of Group A 'fops' — even at five times the recommended rate — an occasional plant showed signs of resistance to a Group A 'dim' herbicide.

This indicated that switching from 'fops' to 'dims' would not be a sustainable control option. The good news was that glyphosate, flamprop-methyl and triallate all gave excellent control.

Program 3.3.1

Contact: Mr Warwick Felton 02 6763 1100

Edwards to educate graingrowers about herbicide resistance," said Mr Felton.

Region North