Weed Control

Herbicide choice

Propyzamide (Kerb) at up to 840 g ha-1 provides additional grass weed control including wild oats and sterile brome plus some broad leaved weeds. Carbetamide (Crawler) is applied pre- or early post-emergence of weeds from November to the end of February. It controls annual meadow-grass, black-grass and barren brome (pre- and post-) and gives some control of volunteer cereals and wild oats post-emergence. It only controls a few broad-leaved weeds, including speedwells (pre- and post-) and cleavers and knotgrass (pre). It can be used on all soil types except soils with more than 10% organic matter.

Figure 3. Control of resistant blackgrass in winter beans. c. Cook et.al., 1991. Aspect Applied Biology (27) Production and protection of legumes p. 161-6.

Cleavers can be a difficult weed to control in many break crops. Clomazone present in both Centium 360 CS and Lingo (clomazone + linuron) plus an off-label approval for prosulfocarb (Defy) provide control of cleavers plus activity on a range of broad leaved weeds.(Figure 4). Defy also offers activity on grass weeds such as loose silky bent and annual meadow grass. Both are residual herbicide for pre emergence use only and can be used on most soil types but clomazone cannot be used on those containing more than 10% organic matter and very light soils and sands. They require good seedbed conditions. Other herbicide possibilities are listed below in Table 1.

Several pendimethalin products have off-label approval for use at 1320gai/ha in winter beans.

Nirvana (imazamox + pendimethalin) can be used pre-emergence in winter beans and provides wide spectrum residual broad-leaved weed control. It shows excellent activity against polygonums, black-bindweed, redshank and knotgrass. Charlock is also effectively controlled as is chickweed. Nirvana also gives improved control of early emerging volunteer oilseed rape when compared to pendimethalin alone and at higher rates can reduce cleaver numbers effectively.

Figure 4. Comparative activity of various herbicides on cleavers in winter beans c. FMC, 2001

Table 1. Activity of various herbicides on broad leaved and grass weeds in field beans.

Contact graminicides also provide good control of grass weeds. ‘Laser’, ‘Pilot’, ‘Fusilade’ and ‘Falcon’ can all be used on beans and provide varying control of most species (Table 2). ‘Aramo’, containing tepraloxydim, has limited scope for dose rate reduction but provides good control of difficult species such as couch and resistant blackgrass (including target site resistance)(Figure 5). ‘Aramo’ should not be used alone for resistant blackgrass as resistance to this group of herbicides develops quickly (within 2 to 3 years of constant lone use) but should be used in sequence with other herbicides, including those mentioned above.

Table 2. Effective dose rates of various contact graminicides for use in broad-leaved crops.

These rates present a guide to the differential susceptibility of specific graminaceous species to each active ingredient and should be used in conjunction with manufacturers recommendations.

Figure 5. Control of resistant blackgrass with various contact graminicides [redrawn from data produced by BASF Ltd, 2000]