Insects And Humans

4.6); (2) reduction in the amount of insecticide applied (in conjunction with a raising 751

of the economic injury threshold and more appropriate timing of insecticide application); (3) increasing the dose applied so that even potentially resistant genotypes are killed; (4) use of insecticide mixtures (the assumption being that the resistance mechanisms for each insecticide will be different and will not occur together in individuals); (5) use of rotations (alternation of the insecticides used) so that resistance to an insecticide decreases during the intervals between its use; (6) the use of synergists which depress the rate of detoxication; and (7) development of new forms of insecticides (but see previous paragraphs) (Georghiou, 1983; Roush, in Pimentel, 1991, Vol. 2; Denholm and Rowland, 1992).

The second problem associated with insecticide use is one already mentioned in Section 2.3, namely, the non-specificity of action of these chemicals, with the resultthat beneficial as well as pest species are destroyed. (Indeed, some were developed precisely because of their "general purpose" nature!) As pest species typically can recover from insecticide application more rapidly than their natural enemies (because of their greater reproductive potential), they rebound with even greater force, necessitating additional insecticidal treatment and increasing costs to the user.

The third problem is the potential health hazard, both direct and indirect, of many of the synthetic insecticides to humans, livestock, and wildlife. The World Health Organization estimated that, on a worldwide basis, about 3 million humans each year are hospitalized due to exposure to pesticides (herbicides, fungicides and insecticides), and about 220,000 persons die, almost all in developing countries (Jeyaratnam, 1990). It should be noted, however, that two-thirds of these fatalities are suicides (Palmborg, in Pimentel, 2002). Indirectly, many millions more, as well as wildlife, receive minute daily doses in their food and drink or in the air they breathe. Indeed, a feature of insecticides originally considered beneficial, namely, their highly persistent (indestructible) nature in the environment, is now realized to be a major detriment to their safety. For example, DDT is highly stable and only slowly degraded in the presence of sunlight and oxygen. Thus, a single spraying in a house or barn may remain effective up to a year, and even outdoor applications (on foliage) may be stable through an entire growing season. Unfortunately, this stability is retained following ingestion or absorption of DDT by living organisms. Thus, DDT tends to be stored in fatty tissue, because of its lipid solubility, and is concentrated as it is transferred from organism to organism in food webs. Recognition of the phenomenon of bioconcentration (biological magnification) via food webs and observation of harmful effects of insecticides in the terminal members of food chains (especially predatory birds) led to enormous public outcry against insecticides. As a result, governments have been forced to examine carefully the balance between the benefits gained and the risks entailed in the use of insecticides, and where necessary enact legislation to protect human interest. One result of this was the banning in 1972 of DDT use in the United States, in all except a very few situations where benefits clearly outweighed risks (Whittemore, 1977). Since then, the list of insecticides whose registration has been fully or partially canceled, suspended pending review, or modified (e.g., by imposing requirements for protective clothing, changes in application method, or application by a certified person) in the United States has grown considerably and now includes virtually all uses of the chlorinated hydrocarbons (Szmedra, in Pimentel, 1991, Vol. 1).

Despite this rather gloomy picture, it must be strongly emphasized that synthetic insecticides have saved and will continue to save millions of human lives and billions of dollars' worth of food and organic manufactured goods. They are still by far the principal method

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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