Weed Management in Beans

The common bean struggles to outcompete weeds due to its slower growth rate compared to most weeds. As a result, it can experience multiple waves of weed growth, leading to substantial decreases in yield. Weeds are plants that grow in unwanted locations and are generally undesirable. They vie with the desired crop for essential resources such as nutrients, moisture, and space, and if left unchecked, they can completely stifle the growth of the crop. Furthermore, weeds serve as hosts for pests and diseases that can have a detrimental impact on overall yield.

Common Bean Weeds

Various types of weeds thrive within a bean crop garden. The following species are commonly found:

Broadleaf weeds

Grass weeds

Pig weed (Amaranthus spp) Crab grass (Digitaria spp)
Sow thistle (Sonchus oleraceae) Barnyard grass (Echinochloa crusgalli)
Mexican marigold (Tagetes minuta) Nutsedge (Cyperus spp)
Devil’s thorn (Emex australis) Wild oat (Avena fatua)
Thorn apple (Datura stramonium) Johnson grass (Sorghum halepense)
Macdonald’s eye (Galinsoga parviflora) Bermuda grass (Cynodon dactylon)
Black jack (Bidens pilosa) Star grass (Cynodon spp)
Nightshade (Solanum nigrum) Guinea grass (Panicum spp)
Oxalis (Oxalis spp) Goose grass (Eleusine indica)

Why is proper weed control important?

The significance of weed management stems from the following reasons:

  1. Weeds substantially diminish crop yield and overall performance.
  2. Weeds act as hosts for pests and diseases.
  3. They engage in direct competition with plants for essential growth factors such as sunlight, water, nutrients, and space. This weakens the plants and makes them more susceptible to pathogen attacks.
  4. Certain weeds possess parasitic qualities, while others can be harmful when consumed by livestock and humans.
  5. Generally, the presence of plants in inappropriate locations detracts from the aesthetics.
  6. Some weeds can harm the crop by producing toxic substances.
  7. They create challenges during harvest, particularly when they develop late in the crop season.

What is the benefit of early/timely weed control?

Early-season weed control is of utmost importance due to the following reasons:

  1. It eradicates competition for light, nutrients, and moisture, allowing the crop to establish itself more effectively.
  2. It safeguards the palatability and nutritional value of the crop.
  3. It significantly reduces opportunities for pests to establish themselves within the crop.
  4. Young weeds are more easily manageable since they absorb and distribute herbicides more efficiently.
  5. Weeding becomes less efficient during periods of drought stress, which predominantly occur later in the season.

Management & Control

To achieve high and quality yields, it is crucial to implement effective weed management. Various methods are utilized, including:

1. Chemical method

This method involves the utilization of herbicides, which is a highly favored approach due to the following reasons:

  1. It is fast and convenient.
  2. There is no risk of mechanical damage to the crop.
  3. It is cost-effective.
  4. It effectively controls weeds that share similar morphological characteristics with the crop.

The following herbicides are recommended for effectively controlling weeds in bean crops:

  1. Catapult® 480SL (Glyphosate – isopropyl ammonium 480g/L):
    • This broad-spectrum non-selective herbicide has enhanced systemic activity, targeting post-emergence broadleaf and grass weeds.
    • Recommended application rate: 200 ml/20L.
    • It is typically used before planting, during land preparation.
  2. Hotline® 450 SC (Linuron 450g/L):
    • This selective herbicide has a broad-spectrum effect, controlling pre-emergence and post-emergence weeds in crops such as carrots, coriander, beans, baby corn, maize, and potatoes.
    • Recommended application rate: 50ml/20L.
    • It is typically applied 2-3 days after sowing.
  3. Bentagran Top® 240EC (Bentazone 150g/L + Fomesafen 70g/L+ Quizalofop-p-ethyl 20 g/L):
    • This selective herbicide is effective against annual weeds in bean fields.
    • Recommended application rate: 50 ml/20L.
    • It is best used when the crop reaches the 2-5 leaf stage.
  4. Forester® 150 EC (Fluazifop – p – butyl 150 g/L):
    • This highly active selective herbicide targets most annual and perennial grass weeds in broadleaf crops, including beans, groundnuts, cotton, tobacco, tomatoes, peppers, cucurbits, brassicas, and other vegetable crops.
    • Recommended application rate: 50-75 ml/20L.
    • It is typically applied as an early post-emergence treatment to actively growing weeds, preferably when they reach the 3-4 leaf stage.

2. Mechanical method

This method entails manually removing weeds utilizing tools and implements such as jembes, hoes, and others. It is essential to execute this task with care to avoid causing mechanical harm to the crop.

3. Cultural method

The cultural practices that contribute to effective weed management encompass the following:

  1. Opting for early maturing bean varieties during planting.
  2. Utilizing clean bean seeds that are devoid of weed seeds.
  3. Employing irrigation water that is free from weed seeds.
  4. Implementing mulching techniques.
  5. Practicing crop rotation.
  6. Adopting narrower row spacing between plants.
  7. Performing hand pulling or uprooting of weeds.
  8. Encouraging early planting of the crop.

Remarks

  1. It is recommended to combine the herbicide with Integra® at a rate of 3 ml/20L. This adjuvant serves as a sticker, spreader, and penetrant, enhancing the effectiveness of the herbicide.
  2. Herbicides should be mixed with clean water for proper dilution.
  3. It is strongly advised to implement an integrated weed management strategy, encompassing multiple approaches for effective weed control.

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