The herbicide Cleranda can only be used with Clearfield varieties of winter oilseed rape, according to Teagasc.
These are varieties with the letters CL clearly marked on the bag.
“The herbicide will work to take out all brassica weeds, except the Clearfield rape crop,” Teagasc tillage specialist, Ciaran Collins explained.
“The big advantage of going down the Clearfield road is that it does offer the opportunity of clearing out brassica weeds that, otherwise, we would have no control over.
“Cleranda is a good, all-round herbicide in any event; it will deal with the likes of groundsel and fumitory in a very effective manner.”
Collins explained that it is a post-emergent herbicide, which is applied at a rate of 2L/ha. It is best to apply the product as soon as possible on actively growing weeds, in order to maximise its efficiency.
Grass weeds in rape crops
Turning to grass weed burdens in rape crops, Collins referenced the suitability of Kerb and Astrokerb.
“Kerb on its own will take out grass weeds very effectively, even blackgrass,” he said.
“The recommended soil temperature is below 10°C. So this can bring us into late October or even early November.
“If growers have done a good job in curtailing broadleaf weeds early in the season, Kerb on its own before Christmas will do a good job in controlling grass weeds in oilseed rape crops.
“Astrokerb at that stage will tackle both grass and broadleaf weeds. However, this option brings with it the restriction of the rape straw not being removed from the field after harvest.”
Pest control
Cabbage Stem Flea Beetle is major pest of oilseed rape crops in the UK. The signs to look out for are shot holes in the leaf canopy.
According to Ciaran Collins, the problems associated with the pest are not as widespread in Ireland, as would be the case in the UK.
“Up to this point, the area of oilseed rape grown in this country has not been that large. There is also an issue associated with the development of pyrethroid resistance in the UK,” Collins said.
“It is important for oilseed rape growers to keep a look-out for the problem gaining a foothold. As a rule of thumb, if the growing crop is being eaten as quickly as it grown, the use of a suitable insecticide is strongly recommended.
“I have not heard, as yet, of Irish farmers having any control difficulties where the management of Cabbage Stem Flea Beetle is concerned.”