Answer:
1. They effect crop productivity
As weeds start to grow in the area where the crops were destined to grow, the production of the crops gets lowered.
2. They deplete the crops from nutrition
The weeds will compete with the crop plants for resources such as minerals from the soil.
3. They will deplete water resources
The weeds will compete with the crop plants for water.
4. Sun-light will be depleted
The weeds will complete with the crop plants for sun light.
5. The crop quality will be affected
As the crop plants will be in competition with the weeds, hence their quality will be affected.
6. They can reduce the biodiversity of crop plants.