15 June 2001

Keeping weeds knocked back

so maize crop can romp away

By Richard Allison

TO ensure good establishment, the month after emergence is critical for weed control in maize, but many producers can still save costs by cutting back on herbicide application rates.

Many maize crops are looking good, but weed growth is picking up where pre-emergent herbicides were not applied, says Devon-based independent consultant John Morgan.

"In the crops first month it is establishing a root system and allowing excess competition from weeds during this period will cut yields or lead to total crop failure in severe cases.

"Achieving maximum yields is crucial this year, with a reduced yield of first-cut grass silage and stocks of forage all used up. The last thing needed is 20% less maize due to poor weed control."

But Mr Morgan advises producers to consider why they are controlling weeds before taking action. Weeds only need control when they compete for nutrients and water; maize particularly hates competition in droughty fields.

"But there is no point in blanket spraying all maize fields. With only one or two weeds for every 10 maize plants, spraying is not needed. Once the canopy closes, cutting out the light, the crop will romp away, growing over 6ft in eight weeks, and overcoming any weeds."

When spraying is needed, he recommends herbicides containing bromoxynil to control atrazine-resistant weeds, such as nightshade. But this can be applied at 1-1.75 litres/ha, less than the recommended 2.4 litres/ha, to small, actively growing weeds. At this stage they are more susceptible to its effect.

"When applied at the recommended rate, action is impressive, with weeds withering rapidly, but you just need enough to stun weeds for long enough for the maize crop to establish," he adds.

"This will cut down the costs of growing maize, making it an even more attractive forage crop." &#42

WEED CONTROL IN MAIZE

&#8226 Consider if it is needed.

&#8226 Critical during first month.

&#8226 Use less herbicide.

Keeping maize weed-free in the early stages of growth can ensure maximum yields, says John Morgan.