Pesticides insects’ resistance

Unfortunately, there is a significant disadvantage resulting from appHcation of insect-resist agents from dyebaths it is impossible to ensure 100% exhaustion (transfer of pesticide from dyebath to fiber) and as a result, there is inevitably some environmental contamination. The extent of concern with this release of insect-resist agent depends on the spectmm of activity of the agent. If it is a broad-spectmm insecticide, especially one with reasonable persistence and lipophilic character, it is Hable to be reasonably toxic to aquatic insects and invertebrates, especially in certain environmental locations where... 

Provides a coordinated crop protection industry response to the development of resistance in insect and mite pests. During the last decade, IRAC has formed several international working gi oups to provide practical solutions to mite and insect resistance problems within major crops and pesticide groups. 

Reductionist approaches to problems in agriculture are seen as symptomatic treatments. There is evidence of the resistance of insects to the pesticides used in combination with GMOs, or to Bacillus thuringiensis that is used in insect-resistant GMOs (Stix 1998, McDonald and Linde 2002). 

Earlier work in this field [28] indicated that acetylcholinesterase enzymes would be suitable biomolecules for the purpose of pesticide detection, however, it was found that the sensitivity of the method varied with the type and source of cholinesterase used. Therefore the initial thrust of this work was the development of a range of enzymes via selective mutations of the Drosophila melanogaster acetylcholinesterase Dm. AChE. For example mutations of the (Dm. AChE) were made by site-directed mutagenesis expressed within baculovirus [29]. The acetylcholinesterases were then purified by affinity chromatography [30]. Different strategies were used to obtain these mutants, namely (i) substitution of amino acids at positions found mutated in AChE from insects resistant to insecticide, (ii) mutations of amino acids at positions suggested by 3-D structural analysis of the active site,... 

The peak period for the use of aldrin and dieldrin was between the late 1960s and the early 1970s throughout various parts of the world (WHO, 1989). The use pattern of aldrin and dieldrin are quite similar. They act as effective contact and stomach poisons for insects. They are used to control soil insects (e.g. grasshoppers and corn rootworm), and protect crops and wooden structures from termites (WHO, 1989). The production of aldrin and dieldrin has decreased since the early 1960s. In the United States, the peak use of aldrin from 19 million pounds in 1966 decreased to 10.5 million pounds in 1970 (USEPA, 1980). During this same period (1966-1970), annual dieldrin use dropped from 1 million to 670,000 pounds. These decreases were primarily due to increased insect resistance to the aldrin and dieldrin, and to the development and availability of more effective and environmentally friendly pesticides (USEPA, 1980). 

In China, the results are dramatic an 80% reduction in pesticide use on small farms planted with GE insect-resistant cotton (Huang et al. 2005 see box 5.3). Similarly, the USDA Economic Research Service reports that pesticide use on corn, soybeans, and cotton declined by about 2.5 million pounds in the United States since the introduction of GE crops in 1996 (Fernandez-Cornejo and Caswell 2006). These results support the notion that GE may radically reduce the negative impacts of farming practices on the environment and spare more land for wildlife (figure 8.1). 

Maize Insect resistant 5.575 million pounds potentially less insecticide active ingredients in 2001 (14.927 million acres) Calculation of pesticide use in a simulation of high insect pest infestation based on historical data, assuming 100% pest control by insect resistant Bt maize. Rationale for the simulation were the low actual infestation levels in recent years that would have obscured the potential change in insecticide use under insect pressure. 

A consistent difference of -78% for pesticide use and environmental impacts between non transgenic- and transgenic, insect resistant- cotton is observed. This consistency relates to the fact that the same insecticides were assumed to have been applied to both non transgenic and transgenic cotton, the impact being caused by different numbers of insecticide sprays that had been applied to these crops. The consistent difference of -100% observed for the impacts of insect resistant maize relates to the feet that Gianessi et al. [7] assumed that this transgenic maize would provide 100% control of European com borer. 

It may come to mind that the introduction of crops that impact pesticide use will inevitably lead to shifts in pesticide residue patterns in foods derived from these crops. In insect-resistant crops, for example, reductions in insecticide sprays against the target insects can be anticipated and concomitant reductions in crop residues. For herbicide toler-... 

While there are some real problems to be solved which involve residues, insect resistance to insecticides is the really big problem. Curiously, the opponents of pesticides fail to measure it in its full dimensions. Resistance of insects to insecticides is a truly growing problem. As long ago as 1908 the repeated use of lime-sulfur sprays in orchards in Clarkson Valley, Washington, selected out a resistant strain of the San Jose scale, which spread and reached southern Illinois orchards in 1920. Then there followed three species of scale insects... 

Agricultural pesticides were found to be effective insect resist agents when applied in emulsion form to wool dyebaths. Dieldrin (Fig. 16.2a), one of the original nerve poisons, is also highly toxic to mammals and aquatic life and its use has been banned in most countries. Products based on permethrin (Fig. 16.2b), a synthetic pyrethroid, are very effective against moth larvae, but have less effect on Anthrenus beetles. To overcome this disadvantage, combination products of permethrin and hexahydropyrimidine derivatives (Fig. 16.2c) have been introduced. 

Jorgen H.V. Stenersen, Dr. Philos., is a professor in ecotoxicology at the Biological Institute, University of Oslo. He graduated as Cand. Real, in biochemistry in 1964 (University of Oslo) and subsequently worked at the Norwegian Plant Protection Institute on research related to possible side effects of pesticides. His first interests were the mechanisms behind insect resistance to insecticides, with emphasis on DDT resistance in stable flies. He was also engaged in studies of the extent of DDT contamination of soil, fauna, and humans as a result of DDT usage in orchards. 

Solanine and chaconine (the main natural alkaloids in potatoes) are cholinesterase inhibitors and were widely introduced into the hviman diet about 400 years ago with the dissemination of the potato from the Andes. They can be detected in the blood of all potato eaters. Total alkaloids are present in potatoes at a level of 15,000 Vig per 200-g potato, which is only about a six-fold safety margin from the toxic level for hximans ( .) Neither alkaloid has been tested for carcinogenicity. By contrast, the pesticide malathion, the main synthetic organophosphate cholinesterase inhibitor present in our diet (17 ug/day), has been thoroughly tested and is not a carcinogen in rodents. Plant breeders have produced an insect-resistant potato however, it had to be withdrawn from the market because of its acute toxicity to hvunans, a consequence of higher levels of solanine and chaconine. 

Cyclodienes (chlordane, aldrin, dieldrin, heptachlor, endrin, mirex, endosulfan, chlordecone). This new class of pesticides appeared on the scene following World War II. Most of them are very stable to sunlight and persistent in soil and they were used to control termites and other insects. Their effectiveness leads to insect resistance and bioaccumulation in the food chain and for these reasons their use was banned between 1984 and 1988. These compounds affect the CNS in the same way, causing tremors, convulsions, and prostration to the maximum extent, depending on the rate and time of exposure. 

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