14 June 2002

Large weeds prevail in maize crops

OPTIONS for controlling large weeds in maize crops are being limited by wet weather and product shortages.

Maize crops are suffering following wet weather and weeds in forward crops are big, but there have been few dry days on which to spray, explains Maize Growers Association agronomist Simon Draper. "Some weeds are bigger than maize plants and a powerful treatment will be needed to control them once ground dries."

But growers have found it difficult to source two products suited to larger weeds, Jester (bromoxynil and prosufuron) and Lentagran (pyridate), he says. Syngenta, which manufactures both, admits Jester supplies are limited this year and this has caused a rush of sales of Lentagran. But there is no limitation on the companys supply of Lentagran, says a company spokesperson.

"But where producers cannot source these products, using bromoxynil and atrazine is likely to be the only option left for larger weeds, but care is needed with dose rates to avoid damaging maize plants."

A high bromoxynil dose rate for good control of large weeds will damage crops – particularly those already looking poor. Therefore, he suggests using a low dose rate of bromoxynil – no more than 0.75 litres/ha – and spraying twice, once to shock weeds and then to kill them. Atrazine can be applied either once with the first spray at 2 litres/ha or twice, using 1.5 litres/ha both times where grass weeds are a problem. &#42