**4. Biological control of** *Tetranychus urticae* **with emphasis on family Phytoseiidae**

Natural enemies have been utilized in the management of agricultural pests for centuries. However, the last 100 years have seen a dramatic increase in their use [26].

#### *Side Effects of Pesticides on Population Growth Parameters, Life Table Parameters… DOI: http://dx.doi.org/10.5772/intechopen.104229*

Biological control, or biocontrol, is the use of an organism to reduce the population density of another organism and it is the core component of IPM that is growing in popularity, especially among organic growers [27]. It is one of the most economical and environmentally harmless methods of pest control for farmers [28]. Two types of biocontrol, natural biocontrol and applied biocontrol, are often distinguished. Natural biocontrol is the reduction of native pest organisms by their indigenous natural enemies. In contrast, applied biocontrol is achieved through human efforts or intervention and consists of three main approaches: conservation, inoculative (classical), and augmentative biocontrol [27]. In some agricultural systems, the natural enemies can suppress the spider mite populations below levels of economic damage [29]. Mite predators play an important role in the IPM of phytophagous mites, particularly in complex cropping systems where they may remove the need for any chemical intervention. Further information on IPM definitions and history can be found [27].

Predatory mites from families Phytoseiidae, Ameroseiidae, Parasitidae, Stigmaeidae, Anystidae, and Bdellidae as natural enemies of Tetranychidae were founded during sampling from Northwestern Iran and Varamin province (2007–2008). Among predator insects, *Stethorus gilvifrons* Mulsant (Coleoptera: Coccinellidae), *Oenopia conglobata* (Linnaeus) (Coleoptera: Coccinellidae), *Exochomus quadripustulatus* (Linnaeus) (Coleoptera: Coccinellidae), *Chrysoperla carnea* (Stephens) (Neuroptera: Chrysopidae), *Scolothrips* sp. (Thysanoptera: Thripidae), and *Orius horvathi* Reuter (Heteroptera: Anthocoridae) were found [30]. Among the predatory mites that have been found, we worked on family Phytoseiidae. Because predaceous mites of the family Phytoseiidae are considered one of the most important groups of natural enemies used in biological control [31]. Indeed, they are considered the most effective natural enemies of tetranychid mites and other microarthropods of economic importance such as thrips [6, 32]. In different countries, phytoseiid mites are successfully used in the management of *T. urticae* in protected environments and open fields [33–36]. Certain phytoseiids consume large numbers of prey and maintain plant-feeding mites at low densities. They have a high reproductive rate, a rapid developmental rate comparable to their prey, a femalebiased sex ratio equivalent to their prey allowing them to respond numerically to increased prey density, and can easily be mass-reared [6, 32]. Furthermore, several species within the family may utilize pollen as a food source and can develop and reproduce on pollen as well. Phytoseiids may persist or even maintain themselves at relatively high densities in the crop at times when their main prey is scarce or absent. Therefore, phytoseiids can prevent prey resurgence, without the normal time lag usually associated with a numerical response [37]. Among the predatory mites of the family Phytoseiidae, we worked on *Phytoseius plumifer* (Canestrini and Fanzago) (Acari: Phytoseiidae) because it is an effective predator of phytophagous mites distributed in several countries such as Iran, Egypt, France, Italy, and Israel [38–40], but there is a little available data about acaricides side effects on this predator's performance [13]. One of the projects was the assessment of lethal and sublethal effects of two commonly used acaricides on *Plumozetes plumifer* [12–14].
