Acaricide

Acaricides are a specific class of pesticides designed to kill members of the subclass Acari. This group includes various types of ticks and mites. These substances are essential tools in both medical science and modern agriculture. While they serve similar goals, the desired selective toxicity often differs between these two fields. Doctors use them to treat health issues, while farmers use them to protect crops and livestock.

Terminology for these substances can become very specific depending on the target. Ixodicides are substances used specifically to kill ticks. Miticides are agents that target mites. A more narrow term, scabicide, refers to agents that target a specific mite called Sarcoptes. Sometimes, the term arachnicide is used for agents targeting arachnids. However, this term is used much more rarely and is often considered informal. In practice, mites and ticks are usually treated as a single group because mites are a paraphyletic grouping.

These chemicals work through many different biological mechanisms. Some act as sprays, such as permethrin. Permethrin is not limited to mites; it also affects insects like lice, cockroaches, fleas, and mosquitoes. Other substances, like diatomaceous earth, work physically rather than chemically. Diatomaceous earth disrupts the cuticles, which are the outer layers, of mites. This process effectively dries the mites out. Other examples include antibiotic miticides, carbamate miticides, and organophosphate miticides.

Specific chemical processes are used to create certain treatments. For example, lime sulfur is used to treat sarcoptic mange. To make it, workers mix hydrated lime, sulfur, and water. They then boil this mixture for about one hour. The chemistry of this mixture depends on the type of lime used. Hydrated lime can bond with about 1.7 times its weight of sulfur. Quicklime is even more reactive, bonding with as much as 2.2 times its weight of sulfur.

When using lime sulfur for skin treatment, precise dilution is required. The strongest concentrate must be diluted at a ratio of 1:32. This mixture is then used to saturate the skin, though care must be taken to avoid the eyes. This treatment is typically applied at six-day intervals. Many other commercial miticides exist for systemic and non-systemic use. These include names like abamectin, acequinocyl, bifenazate, chlorfenapyr, and cypermethrin. Other varieties include clofentezine, cyflumetofen, etoxazole, and fenazaquin.

Medical applications of these substances are quite diverse. A doctor may prescribe ivermectin to treat humans suffering from mite or lice infestations. Agricultural versions of ivermectin are also available for treating infested birds and rodents. Dicofol is another specific miticide used in agriculture. It is structurally related to the insecticide DDT. Dicofol is particularly effective against the red spider mite, known as Tetranychus urticae.

Interestingly, acaricides are even being used to fight rhinoceros poaching. This method involves drilling holes into the horn of a sedated rhino. An acaricide is then pumped into the horn under pressure. The substance is chosen to be safe for the rhino and the local ecosystem. This includes animals like oxpeckers and vultures. If a poacher consumes the horn for traditional Chinese medicine, the chemical acts as a deterrent. It can cause nausea, stomachaches, diarrhea, or even convulsions. However, the quantity is expected to be non-fatal.