29 March 2002

Size does matter in blackgrass control

BLACKGRASS can be too small for effective control with contact-acting herbicides, warns Morley Research Centre.

"If we apply herbicides at the two to three leaf stage, the control we get is better than at one leaf. This shows weed size is becoming critical," says researcher Libby Powell. "You need at least two leaves to get the product into the axil between leaves."

The HGCA-funded work at the Norfolk centre, in conjunction with work at Silsoe Research Institute and the Danish Institute of Agricultural Sciences, also shows spray quality has a big influence on control levels.

Not all air induction nozzles are equal, says Miss Powell. "There is a clear difference in the performance of air induction nozzles when we are trying to hit a small target."

Applications through Billericay BubbleJet 02 nozzles nearly matched that achieved with conventional flat-fan nozzles, but the control offered by other makes trailed significantly (see chart).

While conventional flat-fan nozzles are best for hitting small grass weeds, Billericay 02s could be used at a push if reduced drift is important.

However, Miss Powell says that such findings are specific only to that size and make of nozzle. "We dont yet know how a Billericay 03 or 04 would perform." &#42