Rye-grass might become as difficult to control as black-grass growers are being warned, as reports show evolving resistance to herbicides in rye-grass weed populations in the west of England.
Stuart Jackson, an agronomist at Dow AgroSciences, says growers should aim to optimise rye-grass control.
A report completed in 2010 by Rothamsted Research found enhanced metabolism and ACCase target site resistance (fop and dim) mechanisms in 450 rye-grass samples taken from 33 counties in England.
The first resistance was found in 1990 but no ALS target site resistance has been confirmed to date.
Mr Jackson says: “No surveys have been done since so I do not know whether it [the rate of ALS resistance] has changed.
I suspect the next report will show [overall] resistance in rye-grass has increased.”
Mr Jackson says he believes the agronomy practices which are typically used in areas where rye-grass is a problem weed will lead to an increasing incidence of resistance.
Although rye-grass control can be an issue in the east of England, Mr Jackson says reports show it seems to be a problem where farms are predominately mixed, in the West.
He says: “Rye-grass control seems to be focusing on one application in spring, rather than a programme of herbicides.
“Rye-grass can be more competitive than black-grass. It produces lots of seeds and populations can build very quickly.
“Most rye-grass control happens in spring but this is when the plants are bigger, which is why growers need to start a programme in autumn.
“Growers with a rye-grass problem need to take management strategies of black-grass to rye-grass.”
Trials by Dow AgroSciences have shown control is best when the target weed has a few days of active growth before and after the herbicide application.
In order for active growth to occur, the soil should be about 6degC or above at 10cm (4in) depth, says Mr Jackson.
The company recommends starting a programme of herbicides in autumn, rather than just having one application in spring.
Mr Jackson says: “There is no doubt about it, a programme of herbicides gives better results, but do not delay applications.”
He recommends using three key active ingredients - flufenacet, pendimethalin and prosulfocarb - in the programme.
Cultural control methods, such as delayed drilling, are advisable, says Mr Jackson, who suggests drilling the worst-affected fields last.