Insecticides alternatives

Many people think the ultimate pesticide should be developed from research now being done on certain insect attractants and juvenile hormones. Isolation of naturally occurring sex attractants (pheromones) and juvenile hormones has been accomplished. The attractants could be used to congregate large numbers of insects in one place for extermination by the already existing insecticides. Alternatively, juvenile hormones have been found that prevent maturation or cause sterility in many pests. 

Hurst (19) discusses the similarity in action of the pyrethrins and of DDT as indicated by a dispersant action on the lipids of insect cuticle and internal tissue. He has developed an elaborate theory of contact insecticidal action but provides no experimental data. Hurst believes that the susceptibility to insecticides depends partially on the cuticular permeability, but more fundamentally on the effects on internal tissue receptors which control oxidative metabolism or oxidative enzyme systems. The access of pyrethrins to insects, for example, is facilitated by adsorption and storage in the lipophilic layers of the epicuticle. The epicuticle is to be regarded as a lipoprotein mosaic consisting of alternating patches of lipid and protein receptors which are sites of oxidase activity. Such a condition exists in both the hydrophilic type of cuticle found in larvae of Calliphora and Phormia and in the waxy cuticle of Tenebrio larvae. Hurst explains pyrethrinization as a preliminary narcosis or knockdown phase in which oxidase action is blocked by adsorption of the insecticide on the lipoprotein tissue components, followed by death when further dispersant action of the insecticide results in an irreversible increase in the phenoloxidase activity as a result of the displacement of protective lipids. This increase in phenoloxidase activity is accompanied by the accumulation of toxic quinoid metabolites in the blood and tissues—for example, O-quinones which would block substrate access to normal enzyme systems. The varying degrees of susceptibility shown by different insect species to an insecticide may be explainable not only in terms of differences in cuticle make-up but also as internal factors associated with the stability of oxidase systems. 

The environmental fate and behavior of compounds depends on their physical, chemical, and biochemical properties. Individual OPs differ considerably from one another in their properties and, consequently, in their environmental behavior and the way they are used as pesticides. Pesticide chemists and formulators have been able to exploit the properties of individual OPs in order to achieve more effective and more environment-friendly pest control, for example, in the development of compounds like chlorfenviphos, which has enough stability and a sufficiently low vapor pressure to be effective as an insecticidal seed dressing, but, like other OPs, is readily biodegradable thus, it was introduced as a more environment-friendly alternative to persistent OCs as a seed dressing. 

Example Ester (59) was needed for a photochemical synthesis of chrysanthemate ester (60), a component of the pyrethrin insecticides. The a,B disconnection (59a) gives synthon (61) and aldehyde (62). This 8,y-unsaturated compound could be made by dehydration of (63) as the double bond can appear in only the required position. On page T 149 we discussed the synthesis of (62) by the aldol dimerisation of (64), An alternative strategy is to work at the ester oxidation level (65) which means synthon (66) is needed to combine with (64). 

APCI can help to reduce matrix effects when analyzing for carbamate insecticides. Eor example, when analyzing for methiocarb in citrus products, the apparent recoveries were in the region of 50% with ESI. However, on changing to APCI, the apparent recoveries were increased to 110%. This is an example where APCI can be an alternative API method if matrix effects are a problem with ESI. It is important to note that the analyte must show sufficient sensitivity to both API techniques. 

Pyrethroids are used primarily for the control of household and agricultural insect pests, and secondarily in industrial, stored product, and veterinary applications. They are especially advantageous for use in northern climates because their toxicity is enhanced at low temperatures (Smith and Stratton 1986). Synthetic pyrethroid insecticides, including fenvalerate, are used as alternatives... 

Methoprene is an insect growth regulator and it is also used as an insecticide for cockroaches. The enantioselective isomerization of 7-methoxygeranylamine in the presence of [Rh((+)-BINAP)2]+ followed by acid hydrolysis provides the intermediate, 7-methoxycitronellal, in high yield with high optical purity (97%, 98% ee, Scheme 6).9 Alternatively, methoxylation of ( -citronellalenamine (98% ee) with methanol in the presence of 97% sulfuric acid followed by hydrolysis gives 7-methoxycitronellal in 79% yield without racemiza-tion (Scheme 6).9... 

Resistance to insecticides has drawn global attention since the Korean War in 1950 when the mass use of organic synthetic insecticides, such as DDT and BHC, against agricultural pests and sanitary pests became common. Organophosphorus compounds and carbamates were used thereafter, but invited problems of safety concerns and insect resistance. Synthetic pyrethroids were watched with keen interest as alternatives and have become used widely not only for sanitary pests but also agricultural pests. The development of resistance to synthetic pyrethroids is also not a rare phenomenon and has spread all over the world. 

Methyl bromide has been identified as an ozone-depleting substance and is being gradually removed from world markets. Current legislation and plans call for the elimination of methyl bromide in most industrial countries by 2005, with possible exemptions for quarantine (UNEP, 1996). Currently there is an extensive search worldwide for products that are alternatives to methyl bromide (Kawakami, 1999). These alternatives are broadly defined and include components of management plans such as sanitation, monitoring, contact insecticides, heat treatments, and modified atmospheres, in addition to new fumigants (Batchelor, 1998). 

The problems of diseases and pests will not be solved merely by a chemical formula that inhibits or destroys fungus spores in vitro. A pesticide ought to have the ability to remain on the plant surfaces long enough to prevent or destroy disease agents and to destroy disease vectors before they attack. This is difficult to achieve under the severe weather conditions of the tropical moist forest, the natural habitat of cacao, where the chemical deposited is in many cases washed away by heavy rain. The inherent tenacity of a fungicide could be improved by the addition of adhesives. An effective adhesive or an alternative for use in combination with fungicides or insecticides in the tropics has not yet been developed. 

These high-profile conflicts reemphasize a question raised in Chapter 1. If in some places the public is struggling to ban chemical applications that the industry is fighting to maintain, is it demand or rather supply that drives the behaviors of lawn people, especially their application of insecticides, herbicides, and fertilizers, throughout the United States and Canada More fundamentally, are the risks outlined in Chapter 4 essential to this economy, or incidental to it, an unfortunate market inefficiency that wiU soon be fixed through more and better competition Can the industry produce alternatives How does it communicate and manage risk ... 

Examine all new plant introductions ideally, quarantine new plants for a month. The best biological control is the predatory lady beetle Cryptolaemus montrouzieri optimum temperature 68-77°F (20-25°C). Alternatively, spray with insecticidal soap. Disturb the waxy coating covering colonies before spraying. 

For example, the lack of good alternatives pushed the U.S. Department of Agriculture in 1998 to recommend the use of methyl bromide to treat wood packaging materials from China. A voracious, nonnative insect pest had been found in such packaging materials in 14 states around the United States. The Asian beetle had no known U.S. predators and could cost the United States more than 41 billion in lost forest product, commercial fruit, maple syrup, nursery, and tourist industries. This beetle was an extremely serious insect, and methyl bromide was the only known effective insecticide. Heat treatment was also suggested, but it proved to be more difficult and expensive (Morse 1998). Therefore, methyl bromide as an insecticide was receiving a reprieve. 

A recent study in Ethiopia found the most effective attractant for tsetse flies was acetone, octenol, and cow urine (Belete etal, 2004). An American company markets Mosquito Magnet, a device that purportedly attracts mosquitoes with l-octen-3-ol, heat, carbon dioxide, and water vapor (Enserink, 2002). Simpler traps are being used in East Africa. A black-and-blue cloth, impregnated with insecticide, attracts mosquitoes with acetone and octenol, or alternatively, buffalo urine (Enserink, 2002). 

The use of kerosene as a solvent in paints and insecticides increases the likelihood of exposure by painters, particularly when spray applicators are used (Fidler et al. 1987), and in exterminators. Use of a respirator, alternate application methods (brush or roller), and increased ventilation can all reduce worker exposure to the solvent vapor. 

The avermectins, a family of compounds with potent anthelmintic, insecticidal and acaricidal activity, have vividly demonstrated that fermentation products can have entirely unanticipated activities. Besides their utility in animals, they show great promise for the control of insect pests of plants. Although antibiotics have found only a limited role in the control of plant diseases, the desire to find environmentally acceptable alternatives to the chemicals currently used has prompted new research efforts to discover fermentation products for use as pesticides. 

Uses. As a solvent for fats and oils and as an alternative to turpentine in polishes and paint insecticide... 

The RYMOX technology is a bench-scale technology intended to treat soils and other granular substances contaminated with petroleum products, PCBs, insecticides and other familiar, hazardous natural and man-made organic chemicals. ANI-Recol, Inc., began the development process that has subsequently been taken over by Recol Engineering, Ltd., as an alternative to current ex situ thermal technologies, namely incineration. 

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