ABSTRACT
The term “urea pesticide” includes many compounds with important herbicide and insecticide activities. Chemically, only the presence of a urea moiety is common to all them. Urea pesticides can be classied according to their chemical structures into: substituted ureas, sulfonylureas (SUHs), and benzoylureas (BUIs). Most of the substituted ureas are phenylureas (PUHs) and the rest contain heterocyclic groups. Figure 5.1 shows the chemical pattern for classication of urea pesticides and some examples. PUHs and ureas with heterocyclic groups are herbicides inhibiting photosynthesis by blocking the electron transfer in Photosystem 11 within the chloroplasts of plants. SUHs are herbicides that interfere with the acetolactate synthase (acetohydroxyacid synthase) activity that is related to the biosynthesis of three essential branch-chain amino acids. BUIs act as insect growth regulators, interfering with the chitin formation in the vital insect exoskeleton.
