Question

Define weedicides.

Answer 1

A weed is a plant that is regarded as undesirable in a specific situation, or "a plant that is in the wrong location". Plants that are undesirable in human-controlled environments, such as farm fields, gardens, lawns, and parks, are common examples.
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Complete answer:
Weedicides are weed-killing chemicals that are sprayed on fields to eliminate weeds. A dicot weedicide is $2$, $4$-D ($2$, $4$-dichlorophenoxyacetic acid). Weeds are plants that grow between the rows of crops. Weedicides are chemicals that are sprayed across a field to kill weeds. They will have no impact on crop plants.
Herbicides are used to keep tiny plants in check. Weedicides are used to limit the growth of specific types of weeds. Herbicides used as a pre-plant and pre-emergence treatment can kill weeds before they emerge from the soil, allowing crops to germinate and grow in a weed-free or low-competition environment during their tender and seedling stages. Herbicide is a drug that is used to kill plants, whereas weedicide is a weedkiller.
Glyphosate (Roundup) was first used for nonselective weed management in $1974$. It is currently widely employed for selective weed management in growing crops, thanks to the emergence of glyphosate-resistant crop plants.
Methods of weed control-
1. Preventive control
2. Cultural control
3. Biological control
4. Chemical control
5. Mechanical control

Note:
Benefits of weed:
While the name "weed" has a negative connotation, many plants that are classified as weeds can be useful. Many weeds, like dandelion and lamb's quarter, are edible, and their leaves or roots can be utilised for food or herbal medicine. Burdock is a plant that grows all over the world and is used in East Asia to create soup and medicine. Beneficial insects are attracted to some weeds, which can protect crops from dangerous pests. Weeds can also hinder pests from finding a crop by interfering with the frequency of positive cues that pests use to find food. Weeds can also operate as a "living mulch," providing ground cover that avoids erosion and lowers moisture loss. Weeds can also help to increase soil fertility; dandelions, for example, use their tap root to pull up nutrients like calcium and nitrogen from deep within the soil, while clover has nitrogen-fixing bacteria in its roots, which fertilises the soil directly. The dandelion is also one of several plants that help crops build deeper root systems by breaking up hardpan in too farmed fields.