• Definition

In agronomy, a weed is a herbaceous or woody plant that grows in an agroecosystem without having been voluntarily introduced. The term is more neutral than “weed” because, depending on the context, a weed can be:

• Harmful (competition, pest hosts, yield loss)

• Neutral (no significant effect)

• Useful (erosion protection, habitat for beneficial insects)

Annual broadleaf weeds are a type of weed that is renewed every year from seed. They have two cotyledons when germinating and often have broad, veined leaves.

• Development Lifecycle

1. 1. Germination : usually in early autumn or spring.

   2. Rapid growth : strong installation capacity before or with the main crop.

   3. Flowering and seed production : abundant → strong power of dissemination.

   4. Annual recolonization if not controlled.

• Symptoms

• Competition for water, nutrients, light, → reduced yield.

• Difficulties during mechanical operations (ploughing, harvesting).

• Interference with phytosanitary treatments.

• Risk of harbouring pests or diseases.

• Decrease in the commercial value of crops.

Contributing factors

• Absence or delay in soil work.

• Poor seedling management or lack of vegetation cover.

• Excessive nitrogen fertilization favors certain species.

• Mild climate with early rainfall.

Preventive control

• Clean and sorted seedlings.
• Crop rotation to break the cycle of specific weeds.
• Seeding at optimal density for rapid soil cover.

Mechanical control

• Weeding, hoeing, harrowing or false sowing.
• Early destruction before flowering to avoid going to seed.

Chemical control

• Selective herbicides applied in pre-emergence or early post-emergence.
• Choice of product according to the crop, the stage of the plant and the target species.

Ipm

• Regular monitoring, weed mapping.
• Combination of mechanical, chemical and cultural methods.
• Localized weeding or in strips as needed.

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