Plant species
There are approximately 250,000 species
of plants worldwide; of those,
about 3% or 8000 species behave as weeds.
what
is a
weed?
There are numerous definitions of a weed, including:
-
A plant out of place and not intentionally sown
-
A plant growing where it is not wanted
-
A plant whose virtues have not yet been discovered (R.W.Emerson)
-
Plants that are competitive, persistent, pernicious, and interfere negatively with human activity
Certain characteristics are associated with and allow the survival of weeds. Weeds posses one or more of the following:
-
abundant seed production
-
rapid population establishment
-
seed dormancy
-
long-term survival of buried seed
-
adaptation for spread
-
presence of vegetative reproductive structures and
-
ability to occupy sites disturbed by human activities.
characteristics
of weeds
Problem with weeds
Weeds are troublesome in many ways. Primarily, they reduce crop yield by competing for water, light, soil nutrients, and space. Other problems associated with weeds in agriculture include:
-
reduced crop quality by contaminating the commodity;
-
interference with harvest;
-
serve as hosts for crop diseases or provide shelter for insects to overwinter;
-
limit the choice of crop rotation sequences and cultural practices; and
-
production of chemical substances which are toxic to crop plants, animals, or humans.