Monday, April 14, 2008

But regardless of what it is called or how it is packaged, the basic steps of integrated pest control remain the same:

Identification. Detecting the presence of a pest and identifying it to species. Closely related species may be very similar in appearance, but have significantly different pest potential.
Quantification. Sampling to measure population density. How is population density changing with time?
Determination. Finding out where the population stands relative to economic injury levels. How much more growth potential is left in the population?
Specification. What type of control is warranted? What tools or resources are needed to implement a control operation?
Application. Taking whatever steps are necessary to suppress the pest population.
Evaluation. Confirm efficacy of control tactics by resampling. Re-evaluate the situation and take appropriate actions if needed.

Integrated Control

Just as ground, air, and naval forces are integrated to achieve military objectives, the tactical weapons of pest control can also be integrated to achieve more effective management of pest populations. Development of resistance, effects on non-target organisms, and damage to the environment can all be minimized with selective and judicious use of multi-faceted control tactics. This approach, commonly known as integrated control, requires an understanding of ecological principles as well as a thorough knowledge of the pest's life history and population dynamics.
Integrated pest control is not a new concept. It was commonly practiced in the years before synthetic organic insecticides became widely available. But the old ways were largely abandoned after World War II because chemical weapons were so effective, convenient, and inexpensive. Once we recognized the dangers of over-dependence on a single control strategy, the principles of integrated pest control gained renewed acceptance.
Today, integrated pest control forms the foundation of Integrated Pest Management programs (IPM) that take a comprehensive and multi-disciplinary approach to solving pest problems. Insects, weeds, plant diseases, and even some vertebrate pests (e.g., birds and rodents) are included under the IPM umbrella. These programs emphasize management rather than eradication. They take a broad ecological approach to pest problems, focusing on all members of a pest complex in an effort to identify the optimum combination of control tactics that will reduce pest populations below economic thresholds and maintain these levels with the least possible impact on the rest of the environment. This approach, often called biorational pest control, relies heavily on cultural and biological tactics that are supplemented with carefully timed applications of highly selective chemical weapons.
The complexity of modern IPM programs will continue to increase as we add

Systematic insecticides

Systemic insecticides are a special type of stomach poison. These compounds are absorbed by the tissues of a plant (or animal) without ill effects. Insect pests ingest the insecticide when they feed on the treated organism. Systemic insecticides are sometimes included in the diets of domestic animals to protect them from internal parasites (e.g., cattle grubs and other bot flies). Plant systemics can be incorporated into the soil around ornamentals or bedding plants. The insecticides are absorbed by the roots and translocated to leaves, stems, and flowers. If the insect that feeds on a treated plant doesn't acquire a lethal dose of insecticide, it may at least be deterred from further feeding.
More aboutToxicity Although systemic insecticides are commonly applied to horticultural plantings, they are not as useful for many food crops because the insecticide remains in the food after harvest.
Insecticides contain one or more active ingredients that serve as toxicants (poisons). In their purest form (technical grade), these chemicals may be too toxic, too unstable, or too volatile to be handled or applied safely. Therefore, technical grade insecticide is always mixed with other compounds, known as adjuvants, in order to improve the performance, safety, or handling characteristics of a commercial product. These mixtures (technical grade insecticide plus adjuvants) are known as formulations. Almost anything could be an adjuvant: pumice, ground walnut shells, buffalo gourd root powder, vegetable oil, etc. These compounds are usually listed on the label as "inert ingredients", but they are certainly not inactive. Many adjuvants are proprietary products, protected by patents and closely guarded as industrial secrets. They may represent 90-95% of the total volume of a commercial formulation

Conventional Insecticides -- The Killer Chemicals

Conventional insecticides are among the most popular chemical control agents because they are readily available, rapid acting, and highly reliable. A single application may control several different pest species and usually forms a persistent residue that continues to kill insects for hours or even days after application. Because of their convenience and effectiveness, insecticides quickly became standard practice for pest control during the 1960's and 1970's. Overuse, misuse, and abuse of these chemicals have led to widespread criticism of chemical control and, in a few cases, resulted in long-term environmental consequences.
The effectiveness of an insecticide usually depends on when and where the pest encounters it. Most insecticides are absorbed directly through an insect's exoskeleton. These compounds are known as contact poisons because they are effective "on contact". Other insecticides act as fumigants. They are released in the vapor state (as gases) and enter the insect's body through its tracheal system. Fumigants are most effective when they are used in an enclosed area such as a greenhouse, a warehouse, or a grain bin. Still other compounds must be ingested before they have an effect. These are known as stomach poisons. They often work more slowly than fumigants or contact poisons, but they are still useful for certain types of pest control in homes and businesses

Insect Growth Regulators -- Chemical Control of Development

The enzymes and hormones that regulate developmental processes within an insect's body can sometimes be exploited as chemical control weapons. These compounds, often known as insect growth regulators (IGRs), can be used to stimulate development at inappropriate times or inhibit it at other times. The major groups of IGR compounds include:
Chitin inhibitors. These chemicals (e.g., diflubenzuron and teflubenzuron) inhibit the molting process (apolysis) by blocking the activity of chitin synthetase, an enzyme needed by epidermal cells when constructing a new exoskeleton. Because of this mode of action, chitin inhibitors are highly specific to arthropods. They act rather slowly (2-5 days), but eventually disrupt any process that involves construction of new cuticle (e.g., molting, hatching, pupation). They are most effective when used against the immature stages of a pest. Diflubenzuron, currently registered under the trade name Dimilin, is used for controlling gypsy moths, boll weevils, and various other pests.
Molting Hormone Analogues. Ecdysteroids stimulate the molting process by mimicking the action of molting hormone. Applied to the surface of an insect's body or incorporated into its food, these compounds work by initiating premature ecdysis during the immature stages of development. Ecdysteroid-like compounds have been found in some plants where they evidently serve as a defense against insect herbivores. But despite their potential as insect growth regulators, the ecdysteroids have never been developed into commercial products. Their chemical structural is similar to that of human reproductive hormones (estrogen, progesterone, and testosterone), and like many other steroid compounds, they have the potential to cause cancer and birth defects.
Juvenile Hormone Analogues

Chemosterilants -- Chemical Control of Reproduction

There are over four hundred chemical substances that are known to cause reproductive sterility in insects. Some of these compounds inhibit ovarian growth and development, while others appear to induce fundamental changes in the chemical structure of nucleic acids (DNA and RNA). These changes (mutations) prevent cell division or obstruct normal embryonic development. Chemosterilants belong to several major chemical groups (see Table 1). These compounds are applied directly to the insect or incorporated into food that serves as a bait.
All chemosterilants are extremely hazardous compounds. Their effects are not restricted to insects; they also cause cancer, birth defects, and other mutations in humans and domestic animals. Clearly, these chemicals cannot be dispersed in the environment like other pesticides. Instead, they must be applied under controlled laboratory conditions, usually to insects that are mass reared and released as part of a sterile release program. Although there is much interest in finding a chemosterilant whose effects are limited to insects, no such compound has yet been found.

Semiochemicals -- Chemical Control of Behavior

Much of an insect's behavior is mediated by chemicals in its environment. By turning these chemicals to our own advantage, it is often possible to attract pests to traps or baits, or repel them from our homes, our crops, or our domestic animals. Behavioral messages are delivered by a wide array of chemical compounds. As a group, these compounds are known as semiochemicals. In some cases, they may facilitate communication between the members of a single species (e.g., pheromones) or between members of different species (e.g., allelochemicals). Functionally, semiochemicals may have a wide range of activity. They may serve as attractants or repellents, they may stimulate or inhibit feeding, they may provoke flight or inhibit it, or they may simply elicit behavior patterns at inappropriate times.
Attractant pheromones and allelochemicals can be used as lures or baits in a wide variety of insect traps, or they can be mixed together with toxicants to produce an "elixir of death". Protein hydrolysates, for example, serve as feeding attractants for fruit flies (Rhagoletis spp.). These chemicals can be applied to sticky traps to improve catch, or combined with an insecticide and sprayed on fruit crops to suppress active infestations. Phenethyl propanoate, eugenol, and geraniol can be mixed in a 3.5:3.5:3 ratio and used as an attractant for Japanese beetles (Popillia japonica). These are the active ingredients in the "floral attractant" found in popular bag traps for Japanese beetles. In some cases, chemists have produced synthetic compounds that are even more attractive than naturally occurring chemicals. Trimedlure, a synthetic substitute for alpha-copaene, is produced commercially as an attractant for the Mediterranean fruit fly (Ceratitis capitata). Improved food lures and baits are among the most promising new developments for controlling cockroaches (Blattoidea) in homes and businesses. These are the active ingredients in a new generation of "roach motels" where the insects "check in but don't check out."

Chemical Control

Most people understand that chemical pest control involves the use of chemical substances to kill or disrupt the life cycle of an insect pest. But few people outside the circle of entomology realize just how diverse these compounds are, and in how many different ways they can be used. Although conventional insecticides, the poisons, are still a mainstay of chemical control, they are gradually being superseded by less toxic compounds that disrupt insect development or modify behavior. Some of these new chemical weapons are much safer for the environment and more species specific than most conventional insecticides

Eugenics and Birth Control

Some control tactics are designed to suppress a pest population by altering its genetic makeup and/or reducing its reproductive potential. As a group, these tactics are frequently known as genetic controls because they affect the accuracy or efficiency with which a pest species passes its genetic material (DNA) from one generation to the next. Genetic control usually works in one of two ways: either by causing (inducing) reproductive sterility, or by incorporating new and potentially deleterious genes (or alleles) into the genetic makeup of a pest population. In effect, some members of a pest species are transformed into biological time bombs that eventually destroy other members of their own species. Because of the self-destructive nature of these tactics, they are sometimes called autocidal control.

Insects can be sterilized by exposing them to certain chemical agents (chemosterilants) or to non-lethal levels of ionizing radiation (X-rays or gamma rays). Chemosterilants are really a form of chemical control. They usually work by blocking the onset of sexual maturity, by inhibiting the production of eggs and/or sperm, or by damaging the chromosomes. These compounds will be covered more fully in the section on semiochemical insecticides.
Exposure to radiation also damages chromosomes (usually by breakage or mutation). Since cells with damaged chromosomes cannot divide correctly, they do not form normal gametes or produce viable offspring. Although the susceptibility of each insect species is different, a proper dose of radiation administered at an appropriate stage of development (usually to pupae) can often induce sterility without causing other deleterious side effects. Sterile individuals, reared in large numbers and released into the environment, can mate with "normal" individuals but they produce no viable offspring. The more sterile individuals released, the fewer "normal" matings are likely to occur

Physical and Mechanical Control

Sometimes the most efficient way to kill insects is to stomp on them, literally or figuratively! Physical or mechanical control methods can be as simple as hand-picking the bagworms from a juniper bush, cutting tent caterpillars out of a shade tree, or using a fly swatter and window screens to keep your home free of flying insects. At the other end of the technology spectrum are the electronic bug killers. These high-tech fly swatters produce an ultraviolet glow that attracts flying insects to an untimely death on an electrified grid. Although bug zappers probably kill more beneficial insects than pests, their owners seem to sleep better at night with the reassuring sound of bugs sizzling on the grill. From its inception in the late 1970's, the market for these devices has grown into an industry with annual sales approaching $100 million.
Yellowsticky trap Simple entrapment devices work quite well to control some types of insects. Fly paper and sticky boards, for example, are often used in greenhouses to control whiteflies or leafhoppers. Fruit and shade trees can be protected from various pests (e.g., plum curculio, gypsy moth, and codling moth) by tying a band of folded burlap around the trunk with its open side facing down. As insects climb up the trunk, they are waylaid in the folds of burlap which can be treated with insecticide or inspected daily to collect the pests. Ditches or moats with steep vertical walls are occasionally used as barriers to keep crawling insects (e.g., chinch bugs or whitefringed beetles) from migrating out of one field and into another. Pitfall traps are dug at 3-5 meter intervals in the ditch and filled with kerosene or creosote to kill the pests.

Legal and Regulatory Control

At first, it may seem ludicrous to even contemplate the use of legal measures as pest control strategies -- it's easy enough to pass laws, but how do you train the insects to obey them? In reality, legal sanctions are aimed, not at the insects themselves, but at a range of human behaviors that are most likely to affect the dynamics of pest populations. Legal control tactics, therefore, include all forms of legislation and regulation that might prevent establishment or reduce spread of an insect population.
The Plant Quarantine Act of 1912 was the first legal action taken in the United States to prevent the introduction of pests from foreign countries. This law, and others that followed it, established a network of inspection stations at major ports of entry and gave the federal government authority to organize border quarantines, to inspect all agricultural products, and to restrict entry of any infested goods. Today, these inspections stations operate under the jurisdiction of the Animal and Plant Health Inspection Service (APHIS), a branch of the U. S. Department of Agriculture. APHIS operates about 85 inspection facilities, employs 400-500 inspectors, and intercepts over 20,000 potential pest introductions in an average year. It also operates the Plant Quarantine Training Center where inspectors from all over the world are trained to spot problems before they cross international borders. These agents, now representing nearly 40 countries, cooperate in efforts to limit the spread of indigenous pests under an international agreement that requires inspection and certification of nearly all agricultural commodities prior to export

In general, there are three approaches that plant breeders use to develop resistant cultivars

Antibiosis. Plants produce a wide variety of defensive compounds (allelochemicals) that protect them from herbivores. These compounds may reduce growth, inhibit reproduction, alter physiology, delay maturation, or induce various physical or behavioral abnormalities in herbivores. By purposely selecting for plants with high levels of allelochemicals, or by breeding such plants with less resistant ones, it is often possible to develop new cultivars that resist pest injury yet still retain desirable horticultural characteristics.

Antixenosis. A physical or chemical property of a plant can make it so unpalatable that it is largely protected from herbivore attack. This type of resistance is often known as nonpreference. It may involve the presence of feeding repellents (or the absence of feeding attractants), or it may involve physical traits such as hairs, waxes, or a thick, tough epidermis that do not provide the pest with a desirable feeding substrate. Alfalfa, for example, has been bred with hairy leaves to deter feeding by the spotted alfalfa aphid.
Tolerance. Some plant genotypes are simply able to "tolerate" injurious insects better than others. Tolerant cultivars may be exposed to the same pest populations as susceptible ones, but they do not suffer as much injury. Many varieties of field corn, for example, have fairly narrow, brittle stalks. When attacked by European corn borers, these stalks are further weakened and break easily in a windstorm. This wind damage, known as lodging, makes the corn hard to pick with mechanical harvesters. Plant breeders have largely resolved this problem by breeding for corn with thicker, stronger cornstalks. These tolerant cultivars are still attacked by corn borers, but they "stand up" to the injury and insure a harvestable crop.

Breeding for Host Resistance


Breeding plants (or animals) for resistance to insects is really just another form of biological pest control. Rather than finding insects to attack the pests, breeders look for genetic traits (or combinations of traits) that reduce an organism's susceptibility to attack or injury by its insect pests.

More aboutThe French Grape Crisis This idea was first tested in the 1870's by C. V. Riley, an entomologist who successfully fought a French outbreak of phylloxera (an aphid-like pest of grapes) with resistant North American rootstocks. Indeed, much of the pioneering work in this field has been done with crop plants because they are usually cheaper to breed and easier to manage than livestock. Recent innovations in genetic engineering, however, are likely to accelerate development of resistant genotypes in poultry, swine, and other commercial livestock.

entomologists have concluded that introduced biocontrol agents are most effective when they exhibit the following characteristics:

Narrow host range. Generalized predators may be good natural enemies but they don't kill enough pests when other types of prey are also available.
Climatic adaptability. Natural enemies must be able to survive the extremes of temperature and humidity that they will encounter in the new habitat.
Synchrony with host (prey) life cycle. The predator or parasite should be present when the pest first emerges or appears.
High reproductive potential. Good biocontrol agents produce large numbers of offspring. Ideally, a parasite completes more than one generation during each generation of the pest.
Efficient search ability. In order to survive, effective natural enemies must be able to locate their host or prey even when it is scarce. In general, better search ability results in lower pest population densities.
Short handling time. Natural enemies that consume prey rapidly or lay eggs quickly have more time to locate and attack other members of the pest population. Small populations of efficient natural enemies may be more effective biocontrol agents than larger populations of less efficient species.
Survival at low host (prey) density. If a natural enemy is too efficient, it may eliminate its own food supply and then starve to death. The most effective biocontrol agents reduce a pest population below its economic threshold and then maintain it at this lower equilibrium level

Biological pest control strives to reestablish this balance in one of three ways:


Importation. Foreign exploration is conducted to identify and collect natural enemies in the country from which an exotic pest has been introduced. Following the discovery of a potential biocontrol agent, it undergoes extensive evaluation to insure that its ecology and host range are compatible with the community to which it will be introduced and that it will not become a pest once it is released. Suitable candidates are reared and released in the new habitat in hopes that they will become established and suppress the pest population.
Conservation. A variety of management activities can be used to optimize the survival and/or effectiveness of natural enemies. Conservation activities might include reducing or eliminating insecticide applications to avoid killing natural enemies, staggering harvest dates in adjacent fields or rows to insure a constant supply of hosts (prey), or providing shelter, over-wintering sites, or alternative food sources to improve survival of beneficial species.
Augmentation. Natural enemies that are unable to survive and/or persist in a new environment can sometimes be reared in large numbers and periodically released to suppress a pest population. In some cases, small numbers of a beneficial species are released in several critical locations to suppress local pest outbreaks (an inoculative release). In other cases, larger numbers are released in a single location to flood the pest population with natural enemies (an inundative release

Biological Control

Natural control strategies that employ biological agents for pest suppression are generally classified as biological control tactics. In conventional usage, this term usually refers to the practice of rearing and releasing natural enemies: parasites, predators, or pathogens. A slightly broader definition of "biocontrol" includes any related management activity that is designed to protect or conserve natural enemies.
Biocontrol agents include a wide variety of life forms, including vertebrates, invertebrates, fungi, and microorganisms. These beneficial species are common in most natural communities and, although their presence is often unnoticed, they help maintain the "balance of nature" by regulating the density of their host or prey population. Insect species often become "pests" when this ecological balance is disrupted by natural events or human intervention. Biological pest control strives to reestablish this balance in one of three ways:

Sanitation

Sanitation is another cultural control strategy that may be highly effective for some pests. Removing crop debris from cotton fields after harvest eliminates overwintering populations of pink bollworms (Pectinophora gossypiella), European corn borers (Ostrinia nubilalis), and sugarcane borers (Diatraea saccharalis). Collecting dropped fruit from beneath an apple tree reduces the next season's population of apple maggots (Rhagoletis pomonella), codling moths (Cydia pomonella), and plum curculio (Conotrachelus nenuphar). Shredding or burning the pruning wood from a peach orchard kills shothole borers (Scolytus rugulosus) and lesser peachtree borers (Synanthedon pictipes) that would otherwise emerge and reinfest the orchard. Clean cultivation is often recommended as a way to eliminate shelter and/or overwintering sites for pest populations. Simply tilling or plowing a corn field before winter may disrupt a pest's life cycle by causing mechanical injury, by increasing exposure to lethal cold temperatures, by intensifying predation by birds or small mammals, or by burying the pests deep beneath the soil surface. Populations of corn earworms and European corn borers have been greatly reduced in recent years by community-wide efforts to plow under corn stubble after harvest

What is intercropping?

Intercropping (also known as mixed cropping) is another way to reduce pest populations by increasing environmental diversity. In some cases, intercropping lowers the overall attractiveness of the environment, as when host and non-host plants are mixed together in a single planting. But in other cases, intercropping may concentrate the pest in a smaller, more manageable area so it can be controlled by some other tactic. Strips of alfalfa, for example, are sometimes interplanted with cotton as a trap crop for lygus bugs (Miridae). The alfalfa, which attracts lygus bugs more strongly than cotton, is usually treated with an insecticide to kill the bugs before they move into adjacent fields of cotton.
Safe planting dates for winter wheat In some crops, it is possible to create discontinuity in the pest's food supply simply by altering the time of year for planting or harvesting. This strategy, often known as phenological asynchrony, allows farmers to manage their crop so it remains "out of phase" with pest populations. Sweet corn, for example, can escape most injury from corn earworms (Helicoverpa zea) if it is planted in early spring and harvested before larvae mature. In the Midwest, farmers delay planting winter wheat until after the "fly-free date" to protect their crop from injury by the Hessian fly (Mayetiola destructor). These planting dates are calculated to ensure that wheat is not mature enough to attract egg-laying flies, yet still has enough warm weather to grow sufficiently before winter. Careful timing of harvest dates in alfalfa can cause high mortality in populations of alfalfa weevil (Hypera postica) and alfalfa caterpillar (Colias eurytheme) by removing edible foliage before the larvae have completed development. Harvest timing is often the most practical method available to foresters for controlling bark beetle (Scolytidae) infestations in pine plantations. Since trees become more susceptible to beetle outbreaks as they grow older, good management dictates that timber stands be harvested for lumber before the trees reach full maturity

What is crop rotation?

Crop rotation is one of the oldest and most effective cultural control strategies. Growing a single crop year after year in the same field gives pest populations sufficient time to become established and build up to damaging levels. Rotating the field to a different type of crop can break this cycle by starving pests that cannot adapt to a different host plant. Farmers in the Midwest, for example, can reduce populations of wireworms (Elateridae) and rootworms (Diabrotica spp.) in corn fields by switching to oats, wheat, or legumes. Similarly, the clover root curculio (Sitona hispidula) that feeds exclusively on legumes can be eliminated by switching from clover or alfalfa to corn or small grains. Rotation schemes have also proven successful for controlling pests in pasture lands. Texas cattle fever, a protozoan disease transmitted by cattle ticks, Boophilus annulatus, has been eliminated from the southern United States due, in part, to a diligent campaign of pasture rotation designed to protect beef and dairy herds from tick infestation.
Crop rotation schemes work because they increase the diversity of a pest's environment and create discontinuity in its food supply. As a rule, rotations are most likely to be practical and effective when they are used against pests that:
attack annual or biennial crops
have a relatively narrow host range
cannot move easily from one field to another, and
are present before the crop is planted

Cultural Control

Surprisingly simple modifications of a pest's environment or habitat often prove to be effective methods of pest control. As a group, these tactics are usually known as cultural control practices because they frequently involve variations of standard horticultural, silvicultural, or animal husbandry practices. Since these control tactics usually modify the relationships between a pest population and its natural environment, they are also known, less commonly, as ecological control methods. Simplicity and low cost are the primary advantages of cultural control tactics, and disadvantages are few as long as these tactics are compatible with a farmer's other management objectives (high yields, mechanization, etc.). Unfortunately, there are still a wide variety of insect pests that cannot be suppressed by cultural methods alone

What is Pest Control Tactics?


Pest control tactics were mentioned occasionally in writings of the ancient Chinese, Sumerian, and Egyptian scholars. Many of these tactics were embedded in religion or superstition, but a few had real scientific merit. Predatory ants, for example, were used in China as early as 1200 B.C. to protect citrus groves from caterpillars and wood boring beetles. Ropes or bamboo sticks tied between adjacent branches helped the ants move easily from place to place. A passage in Homer's Iliad (8th century B.C.) describes the use of fire to drive locusts into the sea, and the ancient Egyptians organized long lines of human drovers to repel swarms of invading locusts. Pythagorus, a Greek philosopher and mathematician, was credited with clearing malaria from a Sicilian town during the 6th century B.C. by instructing its residents to drain the marshes. Chemical substances that purportedly killed or repelled insects were in common usage. Many of these were of questionable value, but some worked, and a few are still in use today. Some of the inorganic compounds, such as sulfur and arsenic, have well-established insecticidal activity. And modern science has only recently come to recognize that many plant extracts used by ancient apothecaries (e.g, lemon oil, wormwood, hellebore, fleabane, etc.) do indeed contain compounds with useful activity against insects.

Pest control

Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy
Pest control is at least as old as agriculture[citation needed]. In order to maximize food production, it is advantageous to protect crops from competing species of plants, as well as from herbivores competing with humans.
The conventional approach was probably the first to be employed, since it is comparatively easy to destroy weeds by burning them or plowing them under, and to kill larger competing herbivores, such as crows and other birds eating seeds. Techniques such as crop rotation, companion planting (also known as intercropping or mixed cropping), and the selective breeding of pest-resistant cultivars have a long history.
Many pests have only become a problem because of the direct actions of humans. Modifying these actions can often substantially reduce the pest problem. In the USA, raccoons caused a nuisance by tearing open refuse sacks. Many householders introduced bins with locking lids, which deterred the raccoons from visiting. House flies tend to accumulate wherever there is human activity and is virtually a global phenomenon, especially where food or food waste is exposed. Similarly, seagulls have become pests at many seaside resorts. Tourists would often feed the birds with scraps of fish and chips, and before long, the birds would become dependent on this food source and act aggressively towards humans.
In the UK, following concern about animal welfare, humane pest control and deterrence is gaining ground through the use of animal psychology rather than destruction. For instance, with the urban Red Fox which territorial behaviour is used against the animal, usually in conjunction with non-injurious chemical repellents