OILSEED RAPE growers must understand how herbicides work and how they interact with weed biology to achieve best control of cleavers, say experts.

Temperature, cleavers growth and crop canopy cover are the three most important factors to consider, advised Dow AgroSciences‘s Rene Pollak.

After one of the mildest January‘s ever, cleavers in many southern and central parts of the UK are large, but also softer than usual from slow winter growth, he said.

Herbicide applications should be made before new spring growth prevents adequate spray penetration, he said.

“Where cleavers are not winter hardened and there are the first signs of crop growth, start applying Galera (clopyralid + picloram) at 0.35 l/ha,” Mr Pollak recommended.

Spray uptake is better at temperatures above 5°C, he said, pointing out that growers should not spray if frost is forecast and to wait for milder weather before starting again.

Galera should not be applied once the first crop flower buds are visible above the rape crop, he reminded growers.