Effects of weeds on beans;
- Weeds reduce yield by competing with the bean crop for minerals, light and moisture especially during the early stages of crop growth.
- Some weeds are hosts of pests and diseases.
- A thick growth of weeds in beans makes harvesting difficult.
- The weed seeds and shoots increase labor for winnowing and sorting; they also reduce the purity and/or quality and market price of harvested grain.
These complete their life cycle within one season. In most cases, the seeds produced by annual weeds will germinate very fast and even grow faster than the bean crop itself. These weeds will interfere with the growth of the crop during the critical period of the first four weeks. Annual weeds also produce a lot of seed which can survive and germinate the following season. They include;
- Wandering Jew
- Gallant solder
- Goat weed
- Devil’s horsewhip
- Wild finger millet
These carry on from one season to another. The weeds persist in the bean gardens all the time every year and reproduce through roots, stems (rhizomes), and seeds. It is very difficult to control perennial weeds using mechanical methods because only the top of the weed is cut, the bottom continues consuming the nutrients and water meant for the bean plants. Perennial weeds should be controlled early before the beginning of the planting season. They include;
- African love grass
- Coach grass
- Nutsedge grass
- Spear grass
- Bristy foxtail
Weed control methods
- Manual weed control – involves the use of farm tools and equipment like hoes, rakes, fork jembes and pangas. It should be done carefully to avoid damages to the crop. Always earth up as you help the crop become stronger and help secondary root system develop especially where there has been effects of bean fly attack and root rot.
- Mechanized weed control – involves using mechanized farm equipment such as ox-traction weeders, tractor weeders that remove weeds from the garden. Beans must be planted in rows and weeding takes place at particular crop growth.
- Chemical control – this method of weed control either speeds up, stops or changes the weed’s normal growth patterns. This in turn causes the leaves, stems and roots to dry out. Herbicides are very effective if used properly. Farmers using herbicides need to know the type, the correct dosage and stage to apply the herbicide.
Advantages of chemical weed control
- Herbicides are very effective and take a short time to work.
- Reduces the amount of tillage hence labor-saving.
- There no root damage and no soil disturbance to bring more weeds seeds to the surface for germination.
- Herbicides are a must under zero or minimum tillage.