User:Ari. gg02/Economic entomology

Harmful insects
Insects considered pests of some sort occur among all major living orders with the exception of Ephemeroptera (mayflies), Odonata (dragonflies), Plecoptera (stoneflies), Embioptera (webspinners), Trichoptera (caddisflies), Neuroptera (in the broad sense), and Mecoptera, as well as the lesser known groups Zoraptera, Grylloblattodea, and Mantophasmatodea. Conversely, of course, essentially all insect orders primarily have members which are beneficial, in some respects, with the exception of Phthiraptera (lice), Siphonaptera (fleas), and Strepsiptera, the three orders whose members are exclusively parasitic.

Insects are considered pests for a variety of reasons, including direct damage by feeding on crop plants in the field or by infesting stored products, indirect damage by spreading viral diseases of crop plants (especially by sucking insects such as leafhoppers), spreading disease among humans and livestock, and nuisance to humans. Examples of insects regarded as pests include the phylloxera, migratory locusts, the Colorado potato beetle, the boll weevil, Japanese beetle, aphids, mosquitoes, cockroaches, the Western corn rootworm, and some fly species.

In the past entomologists working on pest insects attempted to eradicate species. This rarely worked except in islands or controlled environments and raised ethical issues. Over time the language changed to terms like control and management. The indiscriminate use of toxic and persistent chemicals and the resurgence of pests in the history of cotton growing in the US has been particularly well studied.

Economic pests
Insects regarded as nuisance pests do not pose as much economic damage as those present in medical and veterinary entomology. Some nuisance insects include silverfish (Zygentoma), cockroaches (Blattodea), many fly species (Diptera), and many ectoparasitic species including fleas (Siphonaptera), bed bugs (Hemiptera), among others. Although these pests do not inflict as much damage to the economy, the Emerald Ash borer (Coleoptera) and the Codling moth (Lepidoptera) do.

The Emerald Ash borer is invasive and damages ash trees in the Ontario region of Canada. These insects leave holes in the wood and speed up the death rate of ash trees. This poses economic damage as well as ecological damage for other organisms that use the ash as a habitat.

Codling moth larvae feed on fresh fruit, specifically apples and thus damage them from the inside out. They also place their frass in the fruit, rendering it not available for human consumption, and allowing for bacteria and fungi to penetrate the fruit.

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Medical veterinary entomology
Medical and veterinary entomology have a strong link to economic entomology. Insects pose both benefits as well as disadvantages to medical and veterinary applications, to humans and to livestock. The Eastern tent caterpillar (Malacosoma americanum) contains a toxin called prunasin that impacts livestock, specifically horses. The caterpillars let out their seta in the animals' forage and when ingested, will pierce the gastrointestinal wall and get through the bloodstream to the reproductive system. This process causes Mare Reproductive Loss Syndrome. The illness facilitated by these insects can induce abortions and has caused up to 300-500 million dollars of loss in Kentucky from 2001-2002.

Blister beetles (family Meloidae) contain a compound called cantharidin, which causes blistering. The blister beetles can be ingested by livestock via the mouth by hiding in hay or forage. When they are ingested, they cause injuries in the digestive system to the host. The insects can also damage crops and garden plants.

Female bot flies (family Oestridae) often lay their eggs on porter flies that will bring their eggs to a host, either human or livestock, and will allow them to hatch. In humans, it causes large and painful bites. In cows, it can cause external damage. Cows' skins are used for leather, and when the bot fly bites cause holes in the skin, it has a high economic cost. Bot flies also affect horses. In Kentucky, the Kentucky derby community relies on horses, and if they ingest the eggs or have porter flies lay eggs on them, it can cause issues with digestion and render them not available for Kentucky derby. Bot flies are common within farms and livestock, as well as in domestic animals, and their potential to create warbles on the animals' skin and fur requires further research in preventing economic damage.