South: Problems ahead for grass weed control?

A trying harvest is at last done. On the plus side we have had some remarkable record-breaking yields. Oilseed rape crops have topped 5t/ha and all other crops apart from spring beans have yielded as well as ever. This despite a very dry spring when spring barley fields looked like fields in a desert in north Africa and the wind that never stopped blowing, drying the soil even more.


Nearly all the rape crop has now been drilled and the earlier-drilled fields are at the two-leaf stage, while later-drilled fields are the cotyledon leaf stage and struggling in dry soils. We need at least 16mm of rain to wet the dry dusty earth to help small plants to grow and more importantly to let the grass weeds and volunteers germinate before drilling cereal crops.


This spells serious problem for grass-weed control since high dormancy has been forecast and at present there is little chitting. It will be imperative to choose the right products for blackgrass control.


Use a product based on flufenacet such as Trooper and use it pre-emergence. Pendimethalin in Trooper will offer some residual control of the later-emerging blackgrass. This year it may be necessary to use a mid-season graminicide with a good residual content to overcome the dormancy problem.


The well consolidated, fine seed-beds coupled with dry weather has meant there is little slug damage in the rape crop, but I advise to keep monitoring the situation as only a few mm of rain will bring slugs close to the surface.


Also remember that a maximum single dose for metaldehyde is 210g/ha, which is also the total dose in any field between August and December.


Seed dressings on oilseed rape have so far worked well and there is no evidence of shot holes to indicate flea beetle damage.



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