5 December 1997

GMrape types see weed spray costs tumble

OILSEED rape varieties which have been genetically modified to be herbicide-tolerant have slashed the cost of oilseed rape weed control by two-thirds.

Compared with a spend of £75-80/ha (£30-32/acre) in conventional varieties, use of a total herbicide in GM herbicide-tolerant rape cost just £25/ha (£10/acre) in trials run by ARC as part of the EU-funded Familiarisation with and Acceptance of Crops incorporating Transgenic Technology (FACTT) project.

The experiments are testing winter and spring varieties modified to withstand the weed-killer glufosinate (as in Challenge).

A single application of the full recommended dose at the four-five leaf stage of the crop gave satisfactory control in the past two seasons work, says ARC director Mike Carver.

"At one site our team was a bit worried about the level of weed regrowth." Split half-dose treatments might be needed in some circumstances, he acknowledges.

Such benefits are not being relayed to the anti-GM lobby, Dr Carver told a regional meeting of the Arable Research Institute Association in Newbury, Berks, last week. "There are clear benefits apparently going unnoticed."

A US survey suggests the use of active ingredients has been cut by 35% through using herbicide tolerant soya, he added. "The significance of that in its widest sense must still be defined. But it is going in the right direction. We cannot deny that the use of herbicides with these crops will drop."

Dr Carver berated critics who offer no alternatives to GM crops as a means of meeting the world need for 50% more food in 25 years. "Why demolish one argument without putting another in its place?"

GM POINTERS

&#8226 Weed control 60% cheaper in herbicide-tolerant crops.

&#8226 split rates an option.

&#8226 GM crop benefits mainly unsung.

&#8226 Critics must show alternatives.