Broadleaf signalgrass, a problem weed in corn production, at its early stage. Dow's latest broad-spectrum herbicide tolerance technology could tackle weeds that have developed resistance to certain types of herbicides Photo: Dow AgroSciences

Dow AgroSciences aims to introduce its new broad-spectrum herbicide tolerance technology in maize by 2011 and in soybeans by 2013. Further details of the genetically modified herbicide-tolerant crops were presented by the company's vice-president of research and development, Dr Daniel Kittle, at Merrill Lynch's agricultural chemicals conference in New York, US, this month.

Dow's "family of traits" will enable the application of a range of broadleaf herbicides and graminicides on crops that they could not previously be used on. The company is validating the use of the technology in six crops: cotton, canola, maize, rice, soybeans and tobacco (Agrow No 515, p 3). It allows the application of the phenoxy auxin herbicide, 2,4-D, or the pyridine auxin herbicide, triclopyr, to control broadleaf weeds in soybeans, Dr Kittle said. Crops can also be modified with tolerance to aryloxypropanoic graminicides for grass weed control.

The ability to confer tolerance to auxin herbicides is important in the context of weed resistance, Dr Kittle pointed out. Several key broadleaf weeds in maize, soybeans and cotton have developed resistance to acetolactate synthase herbicides, such as sulfonylureas, as well as being resistant to, or hard to control, with glyphosate. However, these weed species can still be controlled with auxin herbicides after decades of use, Dr Kittle said.

The combination of tolerance to auxin and aryloxypropanoic herbicides allows control of both grasses and broadleaf weeds. Grass weed resistance is less prevalent as broadleaf weed resistance, but the technology is seen as a useful tool to manage resistance to graminicides. Dr Kittle stressed that the technology was "not a one-trick shot" and that it could be applied to multiple herbicides and modes of action.

Dr Kittle also revealed a few more details about Dow's new family of herbicides for the control of weeds that are resistant to or hard to control with glyphosate (Agrow ibid). The herbicides are suited to rice and other small-grain cereals, and rangeland and pasture markets. He demonstrated the control of the difficult weed, leafy spurge (Euphorbia esula), in rice at an application rate of less than 10 g ai/ha.

Dow's early-stage insecticide for the control of sap-feeding pests (Agrow ibid) would be the company's first product in a market sector worth some $2,000 million. Dr Kittle presented trials data indicating that the insecticide controlled green peach aphids (Myzus persicae) and whiteflies (Trialeurodes spp). Systemic control was superior to standard treatments and the insecticide also has residual action, he pointed out.

Dr Kittle reiterated Dow's plans to introduce its second-generation spinosyn insecticide, spinetoram, and its cereal graminicide, pyroxsulam, in 2008 (Agrow ibid). A few more details also emerged on the company's new Ecosome formulation technology. The process involves "sub-micron" particles of active ingredients being dispersed in water and chemically stabilised with a liquid crystal coating. This allows water-based formulations of ais that used to require solvents, Dr Kittle pointed out. The formulations are "very stable and have excellent mixing properties," he added. Dow is exploring licensing opportunities with formulators and other manufacturers.

Dow again highlighted its collaboration with Sangamo BioSciences on the targeting and regulation of genes in plants. Dow has been able to target genes in canola using Sangamo's ZFN precision protein technology with "exceptional precision", the company says. Moreover, it has carried out the first targeted introduction of DNA into a pre-selected maize gene, Dr Kittle noted. "These scientific milestones mark key events in the application of the ZFN technology toward trait generation and trait stacking, and importantly were achieved across different crop plants core to our healthy oils and crop protection businesses," Dr Kittle said.

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