All
agriculture suffers from pests. From an ecological point of view, pests are undesirable competitors,
parasites, or predators.
Worldwide
only about 100 species of weeds, insects, fungi and microbes cause about 90%
damage to the crops we grow
Pre harvest losses are due to
competition from weeds, diseases, and herbivores; post harvest losses are
largely due to herbivores.
Pests
A
pest is any species that competes with us for food, invades lawns and gardens,
destroys wood in houses, spreads disease, or is simply a nuisance.
The
major agricultural pests are insects
(feeding mainly on the live parts of plants, especially leaves and stems); nematodes (small worms that live mainly
in the soil and feed on roots and other plant issues); bacterial and viral diseases;
weeds (flowering plants that compete
with the crops); and vertebrates
(mainly rodents and birds that feed on grain or fruit).
Weeds
Although
we tend to think that the major pests are insects, in fact, weeds are the major problem in terms of
potential crop loss. Farming produces special environmental and ecological
conditions that tend to promote pests.
There
are about 30,000 species of weeds,
and in any year a typical farm field is infested with between 10 and 50 weed species. Weeds compete
with crops for all resources: light, water, and nutrients. The more weeds, the
less crop. Some weeds can have a devastating effect on crops. Agricultural losses in the US as a result
of weeds exceed $ 16 billion/year.
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