Plant insecticides

Unfortunately, nicandrenone is typical of many instances in the field of natural pesticides where elucidation of chemical structure has not previously received the attention it deserves. However, with the increased availability of powerful instrumental techniques, considerable progress has been made during the past decade. Since the last general review (14), active principles from several more of the time-honored insecticidal plants have yielded to structure elucidation (Table I). 

Hoogendam I, Versteeg JPJ, DeVlieger M. 1965. Nine years toxicity control in insecticide plants. Arch Environ Health 10 441-448. 

Methyl isocyanate is a very dangerous chemical. It was responsible for the deaths of over 2,500 people, perhaps as many as 10,000 people, in the worst industrial accident ever, that of the carbamate insecticide plant in Bhopal, India on December 3, 1984. It is a very toxic chemical. This tragedy is discussed in more detail in Chapter 25. Methyl isocyanate can be made from phosgene and methylamine, which would circumvent use of the isocyanate. Phosgene is made from chlorine and carbon monoxide, but it is also very toxic and dangerous. 

One approach to the discovery of new insecticides which fulfill the criteria of efficacy, safety, selectivity, etc., is through the study of the natural chemical defenses of plants. Extracts of plants have been used as Insecticides by humans since before the time of the ancient Romans, a practice that continues today with many of the 2000 species of plants known to have insecticidal properties (4-5). The use of insecticidal" plants is especially prevalent among subsistence farmers since plants grown locally are cheaper, and sometimes more accessible, than synthetic chemical pesticides. Commercially, however, only a few of these plants. Including those containing pyrethrins, rotenoids, and alkaloids, have been used to any extent in the United States as sources of insecticides (6-8). 

A remarkable number of insecticidal plants seem to have been recognized first as fish poisons. This group has received special scientific attention for example, the already mentioned rotenone and other rotenoids of Perris and Lonchocarpus species (3-6), the lupine alkaloids of Sophora species (13), and a saponin (medicagenic acid) from Medlcago sativa leaves ( ). 

Several nerve toxins produced by plants are interesting because of their insecticidal properties. Insecticidal nicotine is extracted from tobacco. Rotenone (Figure 19.2) is synthesized by almost 70 legumes. This insecticidal compound is safe for most mammals, with the notable exception of swine. The most significant insecticidal plant derivatives, however, are the pyrethrins, discussed below. 

Lime (calcium oxide) is widely used in the production of cement, steel, medicines, insecticides, plant and animal food, soap, rubber, and many other familiar materials. It is usually produced by heating and decomposing limestone (CaCOs), a cheap and abundant mineral, in a calcination process ... 

This is what we did at the American Cyanamid Research Center in Princeton, when we purified methyllycaconitine (an insecticidal plant alkaloid active on insect nicotinic receptors) from Delphinium plants. As reported by Dr. Chalmers in the Tuesday afternoon session, we were able to employ the in vitro cholinergic receptor binding assay to follow the active material present in small quantities on TLC plates. Results were available in a matter of hours. This type of strategy could expedite purifications of active materials from other natural sources. Also, knowing the mode of action of the insecticidal component at an early stage facilitated our decision to purify the active material. 

Agricultural products fertilizers, herbicides, insecticides, plant-growth regulators, etc. 

Benzoxazolone (83) and its 6-methoxy derivative (84) are present in plants and are said to act as fungicides, bactericides and insecticides. Plants also possess the enzyme system which is responsible for the degradation of benzoxazolones. It was to be expected therefore that also synthetic insecticides containing a benzoxazolone moiety will prove to be biodegradable, thus decreasing toxicological hazards. 

The Chinese bittersweet Celastrus angulatus Max., is widely distributed in the People s Republic of China and has been used as a traditional insecticidal plant to protect other plants from insect damage. The plant is finely ground, suspended in water and sprayed over the crop to be protected [127]. 

To date, while no reports of transgenic plants expressing these recently identihed bacterial toxins have been published, Estruch et al. [7] have nevertheless described the use of these genes to generate a second generation of insecticidal plants. 

Three grayanoid diterpenes are the most active constituents from dried flowers of the Chinese insecticidal plant, Rhododendron molle. Rhodojaponin III (49), the major compound, has antifeedant, growth inhibitory, and insecticidal activity against the larvae of Leptinotarsa decemlineata and Spodoptera frugiperda (Klocke et al., 1991). 

Tetrachloroacetophone was combined to triethyl phosphate to form an organophosphate insectide. It induced contact dermatitis in a process operator in an insecticide plant. 

Van Joost T, Wiemer GR (1991) Contact dermatitis from tetrachloroacetophenone (TCAP) in an insecticide plant. Contact Dermatitis 25 66-67... 

The ability to have a healthy child can be affected by chemicals in many different ways. A woman may be unable to conceive because a man is infertile. The production of sperm may be abnormal, reduced, or stopped by chemicals that enter the body. Men working in an insecticide plant manufacturing l,3-dibromo-3-chloropropane (DBCP) realized after talking among themselves that none of their wives had been able to become pregnant. When tested, all the men were found to be sterile. 

Rose, R. I. 2006. Tier-based testing for effects of proteinaceous insecticidal plant-incorporated protectants on non-target arthropods in the context of regularoty risk assessments. GMOs in Integrated Plant Production OBC/wprs Bull. 29 143-150. 

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