18 February 2000

Spring grain cheap options

TIMING and accurate herbicide application have a big influence on the cost of spring cereal weed control, says a Scottish specialist.

"Reductions in dose of up to 50% can be made with some products if attention is paid to weed size and weather conditions at and around spraying time," says Ken Davies of the SAC.

Spray when weeds have only two to three leaves, recommends Dr Davies. That is because less herbicide is required for good control.

"But an early spray should not be at the expense of good conditions," he warns. The faster a weed is growing the easier it is to kill. Cold dry conditions that slow weed growth reduce herbicide effectiveness so higher doses are required.

Cheap standards for broad-leaved weeds in spring cereals include reduced rate combinations of Ally (metsulfuron-methyl), Harmony M (metsulfuron-methyl + thifensulfuron-methyl), mecoprop-P (eg Duplosan) and HBN (eg Oxytril CM) products.

"By varying the combination and doses a broad range can be cheaply controlled if conditions are right. But reduced rate herbicides will not have manufacturers backing and are used entirely at growers risk," notes Dr Davies.

Achieving cheap grass weed control is trickier. For annual meadow grass residual products Avadex (tri-allate), Stomp (pendimethalin) and an off-label recommendation for Tolkan (isoproturon) are available. But dry soils can reduce the performance of this type of product, he warns.

Where wild oats, ryegrass and blackgrass pose problems, Tigress (diclofop-methyl + fenoxaprop-P-ethyl) and Grasp (tralkoxydim) in barley and Cheetah (fenoxaprop-ethyl) and Topik (clodinafop-propargyl) in spring wheat can be used. "But they are not cheap," he says.

For perennial weeds like creeping thistle and docks his best advice is full rate (30g/ha) Ally. These often emerge late so delaying spraying as long as possible will give better control, although other weeds will then be larger.

In some cases a two-spray programme will be needed, using non-sulfonylurea products like Swipe P (bromoxynil + ioxynil + mecoprop-P) plus MCPA or a hormone mixture initially. Ally may only be used once on a crop and not in sequence with Harmony M, he notes. &#42

Fortunes do not have to be spent killing spring cereal weeds, provided conditions are good and spray timings correct, says the SAC.