A pest is any animal or plant detrimental to humans or human concerns, including crops, livestock and forestry, among others. The term is also used of organisms that cause a nuisance, such as in the home. An older usage is of a deadly epidemic disease, specifically plague. In its broadest sense, a pest is a competitor of humanity.
A pest is any living organism, whether animal, plant or fungus, which is invasive or troublesome to plants or animals, human or human concerns, livestock, or human structures. It is a loose concept, as an organism can be a pest in one setting but beneficial, domesticated or acceptable in another.
Pests, such as these termites, often occur in high densities, making the damage they do even more detrimental.
A species can be a pest in one setting but beneficial or domesticated in another (for example, European rabbits introduced to Australia caused ecologicaldamage beyond the scale they inflicted in their natural habitat). Many weeds are also seen as useful under certain conditions, for instance Patterson's curse is often valued as food for honeybees and as a wildflower, even though it can poison livestock.
The term "plant pest" has a specific definition in terms of the International Plant Protection Convention and phytosanitary measures worldwide. A pest is any species, strain or biotype of plant, animal, or pathogenic agent injurious to plants or plant products. Plants may be considered pests themselves if an invasive species.
The animal groups of greatest importance as pests (in order of economic importance) are insects, mites, nematodes and gastropods.
Plant pests can be classed as monophagous, oligophagous, and polyphagous according to how many hosts they have. Alternatively, they can be divided by feeding type, whether biting and chewing; piercing and sucking; or Lapping and chewing. Another approach is to class them by population presence as * key pests, occasional pests, and potential pests. In terms of population biology, there are population growth rate (r) pests; carrying capacity (k) pests; and r-k pests.
Eastern grey squirrels cause damage to homes, particularly to rooflines and attic spaces. They can even inhabit spaces between walls. They are seen as pests in Britain and Ireland because of the decline of red squirrel populations.
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