Pest control, basis

The development of malathion in 1950 was an important milestone in the emergence of selective insecticides. Malathion is from one-half to one-twentieth as toxic to insects as parathion but is only about one two-hundredths as toxic to mammals. Its worldwide usage in quantities of thousands of metric tons in the home, garden, field, orchard, woodland, on animals, and in pubHc health programs has demonstrated substantial safety coupled with pest control effectiveness. The biochemical basis for the selectivity of malathion is its rapid detoxication in the mammalian Hver, but not in the insect, through the attack of carboxyesterase enzymes on the aUphatic ester moieties of the molecule. 

Potato yields, on a national basis, have been increased one third, largely because of more effective pest control. 

Pest control with insecticides is based on the probability that species differ greatly in susceptibility to toxicants and that it is possible to show selective toxicity among species, i.e., controlling one without harming others in the same environment. Evidence has shown that this probability is high, even though its basis is not always understood (Terriere, 1982). In this chapter we will compare the xenobiotic metabolizing enzyme activity of various species to learn how much this may contribute to toxicity differences. 

The Food Quality Protection Act (FQPA) in the USA and the Pest Control Products Act (PCPA) in Canada mandate that potential risks to infants and small children be specifically addressed. When assessing the food use of a pesticide, in order to assure that there is a reasonable certainty that no harm will result to infants and children from aggregate exposure to the pesticide s chemical residues , the FQPA and PCPA in the case of threshold effects call for an additional tenfold margin of safety for the pesticide chemical residue and other sources of exposure to be applied to estimating risks to infants and children. A different margin of safety may be used only if, on the basis of reliable data, such a margin will be safe for infants and children. In Canada, these same requirements also apply to non-food-use pesticides. 

Pyrethroids are widely used to control many agriculturally and medically important insect pests. Due to intensive use of pyrethroids in pest control, many pest populations have developed resistance to these compounds. One major mechanism of pyrethroid resistance, conferred by the knock down resistance gene (Mr), is reduced target site (sodium channel) sensitivity to DDT and pyrethroids. Studies on the molecular basis of Mr and Mr-type resistance in various insects are enhancing our understanding of the structure and function of insect sodium channels and the molecular interaction between insect sodium channels and pyrethroids. In this chapter, I will review recent advances in... 

Residual pesticides provide the basis for the most flexible methods available for pest management in stored products pest control (Champ and Ryland, 1986). 

However, on the basis of past experience, it is reasonable to conclude that with faith, patience, and a sufficient investment, at least some such basic studies of pest biochemistry will pay off in novel and safer pest control strategies. 

Diseases, insects, and weeds are important constrains to crop production their combined effect has been "questimated" at 25-45%, on a world-wide basis. Pesticides comprise one of the major means of pests. In the U.S., insecticides, herbicides, or fungicides are used on more than 90 million hectares of crop land. Percentages of crop area treated with pesticides range from <1 to >90% for crops ranging from pasture to apples. The amount of chemicals used and the seriousness of plant pests mandate that pesticide usage be based on sound biological data and principles. Pest control decisions ideally are based on 1) precise estimates of pest density and... 

The rapid growth of knowledge of natural products with biological activities toward pests now provides an option for treatment, a clearer understanding of biochemical mechanisms, and a basis for biorational approaches to the design of pest control agents Compounds that modify insect behavior are also valuable for pest control because they are normally not toxic to the target insect or to the environment ... 

Farmers are not the only people exposed to agrochemicals. Forty percent of these chemicals are used outside the agricultural industry. Home gardeners use fertilizers and weed killers. Household pest-control agents contain some of the same pesticides used on farms. Chemical workers, professional exterminators, animal-feed mill workers, and some food handlers are other workers who may make contact with these compounds on a daily basis. 

This slow uptake in the pesticide market may be related to the increased costs of the new technology on a product basis (but not on an effect basis) and there is a need for a change in attitude to pest control. However, there are also... 

Putrefied animal matter hcis formed the basis for coyote attractants of possible value in pest control programs. Thus, a putrefied fish formulation has been used as a coyote lure and, more recently, attention has been directed to a fermented aqueous suspension of chicken whole-egg powder, developed initially as an attractant for flies (48). The odor components csf this material have been subjected to detailed chemical analysis ty Bullard et al. (49) and are reported to include volatile fatty acids (77% total 13 acids identified), bases (13% total, mainly trimethylamine, 9 amines identified), and headspace volatiles, including esters, aldehydes, ketones, alcohols, alkyl aromatics, terpenes and sulfur compounds (10% total, 76 compounds identified). Based on these data, a synthetic mixture, "synthetic fermented egg" has been formulated, composed largely of a mixture of ten volatile fatty acids (81%), together with a diverse range of amines and other compounds (50). This mixture was found to be as attractive to coyotes as the fermented preparation itself. The volatile fatty acid component alone was found to exhibit substantial coyote attractancy also (50,51). ... 

It is recommended that aldrin be considered, on an experimental basis, both as a crop insecticide and for the control of subterranean pests. On crops intended for human and animal food no application should be made later than 3 weeks before the harvest of these crops is planned. 

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