Cleavers — Galium aparine — have long caused problems to oilseed rape growers, due to the competitive nature of the weed and the way it can grow across the canopy late in the season. Cleavers are widespread throughout all arable areas of the UK.
Mature cleaver plants can become very large and use the crop for support by growing vigorously across the canopy, ultimately causing serious harvesting problems. Cleavers are very competitive with the crop, depriving it of nutrients, water and light. In non-competitive crops, one cleavers plant per square metre can result in a 5% yield loss.
Inclusion of metazachlor and/or propyzamide in the treatment program can have an effect on cleaver populations, but either of these approaches used alone are unlikely to have a major impact on survival of cleaver plants.
To maximise suppression of cleavers in oilseed rape it is necessary to apply Galera® (active ingredients clopyralid and picloram). Results from replicated trials across the UK and northern Europe have shown that when Galera is applied to well-established and competitive crops of oilseed rape as much as 80% suppression of cleavers can be achieved.
Best results are always achieved from an application of 0.35 L/ha made in the spring. Clopyralid and picloram are both systemic active ingredients that disrupt plant development processes. Visual symptoms include leaf and stem distortion and discolouration of the foliage. Galera is only approved for use on winter oilseed rape varieties. However there is an Extension of Authorisation for minor use (formerly known as ‘SOLAs’) for use on spring oilseed rape. (go to https://secure.pesticides.gov.uk/offlabels/search.asp for more details).