**4. Classification of agrochemical pesticides**

#### **4.1 Synthetic pesticides**

 Synthetic pesticides are classified based on various ways depending on the needs; the three most popular ways to classifying pesticides are the mode of action, the targeted pest species, and the chemical composition of the pesticides [46]. The World Health Organization (WHO) proposed a classification of synthetic pesticides based on their health risks and estimating the median lethal dose (LD50) that produces death in 50% of exposed animals [47].

Pesticide formulation includes emulsifiable concentrates (EC) which are fine suspensions of oil droplets in water and appears milky in color. Wet table powders (WP) are suspensions of fine particles suspended in water. Granules (G) are prepared by mixing the active ingredient with clay for outdoor use. Baits are obtained by mixing the active ingredient with food base especially used for the control of rodents. Dusts (D) must be applied dry and cannot be mixed with water. Fumigants are gaseous insecticides usually packaged under pressure and stored as liquids. Some are tablets or pellets that release gas when mixed with water [31].

Pesticide's mode of action can be classified as contact (non-systemic) and systemic pesticides [31].

 Garcia et al. [33] describe that pesticides are classified by target organism (e.g., insecticides, herbicides, fungicides, miticides, nematicides, molluscicides, and rodenticides) and chemical structure (organochlorines (OCs), organophosphates (OPs), carbamates, and pyrethroids).

 Organochlorines are organic compounds with five or more chlorine atoms. They were the first synthetic organic pesticides to be used in agriculture and in public health; they were widely used as insecticides for the control of insects.

#### *4.1.1 Organophosphates*

Organophosphates are phosphate acid esters or thiophosphoric acid esters their original compounds were highly toxic to mammals. Organophosphates are the general name for organic derivatives of phosphorus. They are the most commonly used insecticides in the world because their unstable chemical structure leads to rapid hydrolysis and little long-term accumulation in the environment [48]. Organophosphate manufactured since then is less toxic to mammals but toxic to target organism, such as insects. Some examples of organophosphate pesticides are malathion, parathion, diazinon and dichlorvos, tribufos (DEF), vamidothion, thiometon, and oxydemeton methyl.

#### *4.1.2 Carbamates*

Carbamates are a class of insecticides structurally and mechanistically similar to organophosphate (OP) insecticides. Carbamates are N-methyl Carbamates derived from a carbamic acid and cause carbamylation of acetylcholinesterase at neuronal synapses and neuromuscular junctions, some of the carbamates are aldicarb, carbaryl, oxamyl and terbucarb [49].

#### *4.1.3 Pyrethroids*

 Pyrethroids are among the most frequently used pesticides and account for more than one-third of the insecticides currently marketed in the world [50]. Pyrethroids are known for their fast knocking down effect against insect pests, low mammalian toxicity, and facile biodegradation [51]. The synthetic pyrethroids with the basic structure of cyclopropane carboxylic ester are called type I pyrethroids. The pyrethroid insecticides were enhanced further by the addition of a cyano group at the benzylic carbon to give α-cyano are called type II, e.g., cyphenothrin and cypermethrin, tefluthrin.

The other major practice to pest management is biopesticides that are also a type of integrated pest management (IPM): biopesticides generally perform particularly well in IPM systems. With their lower toxicity profile, they are

*Pesticides, Anthropogenic Activities, and the Health of Our Environment Safety DOI: http://dx.doi.org/10.5772/intechopen.84161* 

 compatible with the use of classical biological control agents. Because they often are most effective at low pest pressures, they are well suited to be used in combination with scouting and monitoring activities, which detect pest problems before they are out of control. As well, IPM programs which include the rotation of biopesticides with conventional chemical pesticides can reduce reliance on single chemistries and delay the development of resistance within pest populations [52].

### **4.2 Biopesticides fall into three major classes**


Tri-State Greenhouse IPM Workshop [6] reported that, recently, new substance has been reported as promising compounds for use as biopesticides. Extract of the Saponaria officinalis root and the nanoparticles showed a very good acaricidal efficacy [57], the fungus strains of *Talaromyces flavus* SAY-Y-94-01 [58], the fungus *Trichoderma harzianum*, fermentation products of the bacterium *Lactobacillus casei* strain LPT-111 [6], stilbenes accumulated in grape canes [50], and olive mill wastes [51].

In recent years, a new technology began to take place in IPM program; it could contribute to the development of less toxic biopesticides with favorable safety profiles and increased stability of the active agent, enhanced activity on target pest, and increased adoption by the end-users [43, 59]. Nanotechnology will contribute to making agriculture eco-friendlier and more profitable by reducing the usage of crop protection chemicals. Intelligent delivery of fertilizers, pesticides, and growth regulators, including nanosensors for real-time monitoring of soil conditions, crop growth, and pest and disease attack, is made possible through the development of nanodevices and products [60].
