Satisfactory weed control is essential to ensure that:
- the crop is able to achieve its full yield potential
- the combining and drying operation is not slowed down by the presence of green material at harvesting
- quality is maintained by producing a seed sample that does not have an admixture of weed seeds in it.
Beans are very susceptible to weed competition in their early stages of growth and therefore a good weed control programme is essential.
Perennial weeds and scutch grass should be controlled in the previous crop or stubble with an application of glyphosate.
It is essential that pre-emergence residual herbicides are used as Basagran is the only approved post-emergence herbicide which controls emerged broad-leaved weeds and it has a very limited weed spectrum.
Pre emergence residual products work best on fine seedbeds with some moisture after spraying. Rolling post sowing helps the activity of pre-emergence herbicides by breaking up the clods
Pre-emergence weed control will be based around pendimethalin products with 800g/ha + of ai required for persistent control. Imazamox, clomazone and prosulfocarb are potential partners to broaden the weed spectrum especially where charlock, volunteer oilseed rape, cleavers, mayweeds and groundsel are present
Avoid spray overlaps as bleaching can occur. There should be 13 mm clay cover over the emerging bean to avoid crop damage.
Grass weeds can be controlled effectively with an appropriate graminicide.
Products that are cleared for use on beans are available at: www.pcs.agriculture.gov.ie