Variable crops present weed control challenge

Cold soils, protracted drilling concerns around emergence and the need to re-drill many crops have resulted in crops of great variability this season.

Beet root weed controlBeet root weed control

Achieving effective weed control in these circumstances has been difficult and many growers will be wondering what to do next.

A survey of growers reveals just how variable crops are. In areas where crops achieved a trouble-free start there are superb stands with six to eight true leaves or more while others have fared less well and can be as much as several weeks behind.  Within fields, crop progress too is inconsistent.

Where crops have established well finishing off weed control should be relatively straightforward as canopies will soon be closing and one further spray of Betanal maxxPro (phenmedipham + desmedipham + ethofumesate + lenacil) should complete the programme. In such circumstances, you can afford to wait for a final flush of weeds before applying this final dose.

It is worth noting however, that the bigger the weeds, the higher the dose needed.  Where Betanal maxxPro has been the core of the programme to date, the final dose should take into account weed growth stage and the maximum permitted total dose per crop of 4.5 L/ha.

Where crop growth is variable or ‘patchy’, a more considered judgement will be required. There are two options; either delay the final application of Betanal maxxPro, which has been found to be just as effective against bigger weeds as it is with smaller or, if crop growth is particularly slow, add in a suitable residual such as metamitron. 

With the advent of warmer weather crops will begin moving faster and so the focus should switch to tall weeds. Observations suggest that volunteer oilseed rape, fat-hen and scarlet pimpernel are widespread. The latter is of little significance as it is low growing and not competitive, but where the former are present it is worth waiting until they have passed the cotyledon stage to ensure full control.