Australian growers will plant about 60% of their cotton area this season to Roundup Ready varieties, in line with a global trend in the uptake of Monsanto’s herbicide tolerance technology (Roundup Ready®).

USDA survey data of herbicide tolerant cotton in the US show that planting increased from 10% of the US area under cotton in 1997 to 59% in 2003.

This is a faster adoption rate than achieved by insect resistant Ingard® (Bt) cotton, which in the US climbed from 15% in 1997 to 41% in 2003, said Cotton Seed Distributors general manager Adam Kay.

Other US Department of Agriculture estimates show that 80% of the 73 million acres of soybeans in the US are also Roundup Ready soybeans.

Mr Kay said he expected Roundup Ready varieties to cover about 60% of the area planted to cotton in Australia this season.

While Roundup Ready technology has become an important part of the cotton farming system, some are warning farmers about relying on it too heavily at the risk of resistance to Roundup developing among weed species.

In 1996, Australia was the first to note weed resistance to glyphosate in rigid ryegrass in a few grain and sorghum fields.

"Farmers are planting too many Roundup Ready crops," says Stephen Powles, an expert on weed resistance at the University of Western Australia.

"I think the problem will become a crisis," he told the Associated Press last month, but there has been no noted weed resistance to Roundup in cotton production areas.

Mr Kay said Roundup Ready technology would be important this cotton season, when weed pressure and diversity are expected to be a problem.

“Roundup Ready varieties have many benefits, one of the most significant being the flexibility to plant later than normal, which can be a significant aid to disease prevention and control,” he said.

“RR varieties allow glyphosate to be sprayed over the top in the critical early stages of the plant’s growth, facilitating plant establishment, and also as a shielded spray beyond the four-leaf growth stage.

“This can lead to important savings and benefits in terms of reducing residual herbicide applications, and in increasing the grower’s ability to check difficult to control weeds,” Adam Kay said.

CSD has two conventional Roundup Ready varieties currently available: Sicot 189RR and Sicala V-2RR; and three Roundup Ready Ingard varieties: Sicala V-3RRi, Sicala 40RRi and Sicot 289RRi.

In the following year, for plantings late in 2004, Bollgard®II Roundup Ready varieties will also be available.