Құбылыстардың адамға зиянды түрлері

Organism harmful to humans/our concerns

A pest is any organism harmful to humans or human concerns. The term is particularly used for creatures that damage crops, livestock, and forestry or cause a nuisance to people, especially in their homes. Humans have modified the environment for their own purposes and are intolerant of other creatures occupying the same space when their activities impact adversely on human objectives. Thus, an elephant is unobjectionable in its natural habitat but a pest when it tramples crops. Some animals are disliked because they bite or sting; snakes, wasps, ants, bed bugs, fleas and ticks belong in this category. Others enter the home; these include houseflies, which land on and contaminate food, beetles, which tunnel into the woodwork, and other animals that scuttle about on the floor at night, like cockroaches, which are often associated with unsanitary conditions. Agricultural and horticultural crops are attacked by a wide variety of pests, the most important being insects, mites, nematodes and gastropod molluscs. The damage they do results both from the direct injury they cause to the plants and from the indirect consequences of the fungal, bacterial or viral infections they transmit. Plants have their own defences against these attacks but these may be overwhelmed, especially in habitats where the plants are already stressed, or where the pests have been accidentally introduced and may have no natural enemies. The pests affecting trees are predominantly insects, and many of these have also been introduced inadvertently and lack natural enemies, and some have transmitted novel fungal diseases with devastating results. Humans have traditionally performed pest control in agriculture and forestry by the use of pesticides; however, other methods exist such as mechanical control, and recently developed biological controls.

A pest is any living thing which humans consider troublesome to themselves, their possessions, or the environment. Pests can cause issues with crops, human or animal health, buildings, and wild areas or larger landscapes. An older usage of the word "pest" is of a deadly epidemic disease, specifically plague. In its broadest sense, a pest is a competitor to humanity. Pests include plants, pathogens, invertebrates, vertebrates, or any organism that harms an ecosystem. Many people appreciate birds in the countryside and their gardens, but when these accumulate in large masses, they can be a nuisance. Flocks of starlings can consist of hundreds of thousands of individual birds, their roosts can be noisy and their droppings voluminous; the droppings are acidic and can cause corrosion of metals, stonework, and brickwork as well as being unsightly. Pigeons in urban settings may be a health hazard, and gulls near the coast can become a nuisance, especially if they become bold enough to snatch food from passers by. All birds are a risk at airfields where they can be sucked into aircraft engines. Woodpeckers sometimes excavate holes in buildings, fencing and utility poles, causing structural damage; they also drum on various reverberatory structures on buildings such as gutters, down spouts, chimneys, vents and aluminium sheeting. Jellyfish can form vast swarms which may be responsible for damage to fishing gear, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea. Many of the animals that we regard as pests live in our homes. Before humans built dwellings, these creatures lived in the wider environment, but co evolved with humans, adapting to the warm, sheltered conditions that a house provides, the wooden timbers, the furnishings, the food supplies and the rubbish dumps. Many no longer exist as free living organisms in the outside world, and can therefore be considered to be domesticated. The St Kilda house mouse rapidly became extinct when the last islander left the island of St Kilda, Scotland in 1930, but the St Kilda field mouse survived.

[[File: Tribulus terrestris nutlets in foot, Marfa, Texas. JPG|thumb|Caltrop, Tribulus terrestris, is sometimes considered a pest plant because of its sharp spiny burrs, shown here in a person's foot. An example of such a plant prescribed under this regulation is caltrop, Tribulus terrestris, which can cause poisoning in sheep and goats, but is mainly a nuisance around buildings, roadsides and recreation areas because of its uncomfortably sharp spiny burrs.

Disease causing pathogens such as fungi, oomycetes, bacteria, and viruses can cause damage to crops and garden plants. Worldwide, agricultural pest impacts are increased by higher degrees of interconnectedness. This is due to the increased risk that any particular pest problem anywhere in the world (as a system) will propagate across the entire system.

thumb|upright|The large and directly defensive thorn like stipules of Vachellia collinsii are hollow, offering shelter for ants, which further protect the plant against herbivores. Plants have developed strategies that they use in their own defence, be they thorns (modified stems) or spines (modified leaves), stings, a thick cuticle or waxy deposits, with the second line of defence being toxic or distasteful secondary metabolites. Mechanical injury to the plant tissues allows the entry of pathogens and stimulates the plant to mobilise its chemical defences. The plant soon seals off the wound to reduce further damage. Plants sometimes take active steps to reduce herbivory. Macaranga triloba for example has adapted its thin walled stems to create ideal housing for an ant Crematogaster spp., which, in turn, protects the plant from herbivores. In addition to providing housing, the plant also provides the ant with its exclusive food source in the form of food bodies located on the leaf stipules. Similarly, several Acacia tree species have developed stout spines that are swollen at the base, forming a hollow structure that provides housing for ants which protect the plant. These Acacia trees also produce nectar in nectaries on their leaves as food for the ants.

Pest ranges are heavily determined by climate. The most common example for the longest time has been rainfall: Although drought stress weakens crop disease resistance, drought also retards contagion and infection; and some variability in precipitation is universal. More recently climate change has been rapidly altering ranges, mostly by pushing them towards the poles (both North and South). From 1960 2013 ranges have shifted poleward by per year albeit with significant differences between taxa. (Especially in the case of viruses and nematodes which show the opposite trend, toward the equator. This may be due to their lack of airborne dispersal, so their trend conforms with the trend of human aided dispersal; or identification difficulties in the field.) In Europe, crop pests are expected to burgeon as the vertebrate predators which control them are expected to be suppressed by future climatic conditions.

thumb|Alligator weed, a native of South America, is an invasive species in many other countries and is considered a noxious weed as it is harmful to aquatic ecosystems, recreational activities, and favours the spread of mosquitoes. Control is difficult. A weed is a plant considered undesirable in a particular situation; the term has no botanical significance. Often, weeds are simply those native plants that are adapted to grow in disturbed ground, the disturbance caused by ploughing and cultivation favouring them over other species. Any plant is a weed if it appears in a location where it is unwanted; Bermuda grass makes a good lawn plant under hot dry conditions but become a bad weed when it out competes cultivated plants. A different group of weeds consists of those that are invasive, introduced, often unintentionally, to habitats to which they are not native but in which they thrive. Without their original competitors, herbivores, and diseases, they may increase and become a serious nuisance. One such plant is purple loosestrife, a native of Europe and Asia where it occurs in ditches, wet meadows and marshes; introduced into North America, it has no natural enemies to keep it in check and has taken over vast tracts of wetlands to the exclusion of native species.

thumb|right|Termites can cause serious structural damage. Animals able to live in the dry conditions found in buildings include many arthropods such as beetles, cockroaches, moths, and mites. Another group, including termites, woodworm, longhorn beetles, and wood ants cause structural damage to buildings and furniture. The natural habitat of these is the decaying parts of trees. The deathwatch beetle infests the structural timbers of old buildings, mostly attacking hardwood, especially oak. The initial attack usually follows the entry of water into a building and the subsequent decay of damp timber. Furniture beetles mainly attack the sapwood of both hard and soft wood, only attacking the heartwood when it is modified by fungal decay. The presence of the beetles only becomes apparent when the larvae gnaw their way out, leaving small circular holes in the timber. Carpet beetles and clothes moths cause non structural damage to property such as clothing and carpets. It is the larvae that are destructive, feeding on wool, hair, fur, feathers and down. The moth larvae live where they feed, but the beetle larvae may hide behind skirting boards or in other similar locations between meals. They may be introduced to the home in any product containing animal fibres including upholstered furniture; the moths are feeble fliers but the carpet beetles may also enter houses through open windows. Furniture beetles, carpet beetles and clothes moths are also capable of creating great damage to museum exhibits, zoological and botanical collections, and other cultural heritage items. Constant vigilance is required to prevent an attack, and newly acquired items, and those that have been out on loan, may need quarantining before being added to the general collection. There are over four thousand species of cockroach worldwide, but only four species are commonly regarded as pests, having adapted to live permanently in buildings. Considered to be a sign of unsanitary conditions, they feed on almost anything, reproduce rapidly and are difficult to eradicate. They can passively transport pathogenic microbes on their body surfaces, particularly in environments such as hospitals, and are linked with allergic reactions in humans. thumb|Flour beetles are important commercial pests of grain storage. Various insects attack dry food products, with flour beetles, the drugstore beetle, the sawtoothed grain beetle and the Indianmeal moth being found worldwide. The insects may be present in the warehouse or maybe introduced during shipping, in retail outlets, or in the home; they may enter packets through tiny cracks or may chew holes in the packaging. The longer a product is stored, the more likely it is to become contaminated, with the insects often originating from dry pet foods. Some mites, too, infest foodstuffs and other stored products. Each substance has its own specific mite, and they multiply with great rapidity. One of the most damaging is the flour mite, which is found in grain and may become exceedingly abundant in poorly stored material. In time, predatory mites usually move in and control the flour mites.

Forest pests inflict costly damage, but treating them is often unaffordable, given the relatively low value of forest products compared to agricultural crops. It is also generally impossible to eradicate forest pests, given the difficulty of examining entire trees, and the certainty that pesticides would damage many forest organisms other than the intended pests. Forest integrated pest management therefore aims to use a combination of prevention, cultural control measures, and direct control (such as pesticide use). Cultural measures include choosing appropriate species, keeping competing vegetation under control, ensuring a suitable stocking density, and minimizing injury and stress to trees.

Pest control in buildings can be approached in several ways, depending on the type of pest and the area affected. Methods include improving sanitation and garbage control, modifying the habitat, and using repellents, growth regulators, traps, baits and pesticides. For example, the pesticide Boron can be impregnated into the fibres of cellulose insulation to kill self grooming insects such as ants and cockroaches. Clothes moths can be controlled with airtight containers for storage, periodic laundering of garments, trapping, freezing, heating and the use of chemicals. Traditional mothballs deter adult moths with strong smelling naphthalene; modern ones use volatile repellents such as 1,4 Dichlorobenzene. Moth larvae can be killed with insecticides such as permethrin or pyrethroids. However, insecticides cannot safely be used in food storage areas; alternative treatments include freezing foods for four days at or baking for half an hour at to kill any insects present.