19 June 1998

Blackgrass pinpoint

A TEST which detects herbicide resistance in blackgrass early in the growing season so alternative control strategies can be adopted is being developed by Nottingham Trent University and Harper Adams College, with HGCA support.

The test, which measures glutathione S-transferase (GST) levels in the weed, can pinpoint plants resistant to chlorotoluron, fenoxaprop-ethyl and isoproturon.

"GSTs are a group of enzymes involved in herbicide metabolism," says John Reade of NTU. "As there is a correlation between GST activity and resistance, we have developed a test which measures GST levels.

"Resistant biotypes have approximately double the GST activity of susceptible ones, so we have concentrated on developing a quick, portable test which can be used in the field."

Mr Reade is confident the test could eventually be used by growers and advisers in the autumn, so preventing resistant blackgrass affecting the crop and shedding seed.

"It gives growers time to take appropriate action," he says. "By using it early in the season, before post-emergence spraying has begun, other tactics can be employed if resistance is confirmed."

He believes that the test should be inexpensive because the technology it uses already exists.

Early season testing for herbicide-resistant blackgrass should aid control, says John Reade.