Fsb

748 and heptachlor, and more than 8 billion pounds were produced between 1950 and 1990

(Casida and Quistad, 1998). The use of chlorinated hydrocarbons in the western world was severely reduced, beginning in the 1970s, following the development of resistance and the recognition of the health hazards that these highly persistent insecticides pose (see below). Some, however, remainthemajor insecticides in some developing countries. Though discovered in 1937, organophosphates such as TEPP, diazinon, dichlorvos, parathion, and malathion did not come to prominence as insecticides till the mid-1960s. They continue to play a massive role, especially in agricultural pest control, with about one half of the top 20 sales list being organophosphates (Casida and Quistad, 1998). Carbamates, for example, sevin, isolan, and furadan, originated in the 1940s but their impact on the insecticide scene was not seen until the late 1960s. They remain important with 4 representatives in the top 20 insecticides sold. For details of structure, physical properties, formulation, lethal doses, usage, etc., consultFronk, in Pfadt (1985), Volume 12 of Kerkut and Gilbert (1985), Hassall (1990), and Szmedra, in Pimentel (1991), Vol. 1.

The search for suitable synthetic insecticides continues today, though at a somewhat reduced rate because the profitability of such ventures for industrial concerns has greatly diminished, for a variety of interrelated reasons. The primary reasons are (1) the time and cost of discovery, development, and registration of an insecticide, estimated at an average of 7 years and US$35-45 million, with an additional US$55-65 million for the cost of a production plant [by comparison, the total cost of developing a new drug is US$360 million (Casida and Quistad, 1998)]. Only 1 in 15,000-20,000 candidate chemicals ever reaches the marketing stage; (2) the relatively short "life expectancy" of an insecticide because of the development of resistance by its target organisms and/or its becoming an environmental hazard. In contrast to the situation 20-25 years ago, companies now seek to maximize sales within 3-5 years after registration; and (3) a general unwillingness of government agencies to grant registrations for use of new insecticides (and, for that matter, other types of chemical pesticides), as a result of pressure from environmentalists, special interest groups, and the general public. As a result, some of the largest companies in the chemical industry have either considerably reduced or abandoned research into the development of new insecticides (Brown, 1977; DeBach and Rosen, 1991; Dent, 2000).

Paralleling research into new synthetic insecticides has been the discovery of several additional groups of naturally occurring compounds with insecticidal activity, for example, the avermectins, spinosyns, and azadirachtins. Avermectins, a mixture of natural products from the soil actinomycete Streptomyces avermitilis, were discovered in the 1970s during screening tests for natural antihelminthic compounds (Lasota and Dybas, 1991). It was also observed that they were potent insecticides and acaricides, and subsequently ivermectin and abamectin were registered for use with domestic animals and some household pests. Ivermectin is also used to control onchocerciasis in West Africa and Latin America. Though avermectins are quickly degraded in ultraviolet light and are strongly bound to soil particles, two features that improve their safety against non-target organisms, there are situations in which they may pose problems. For example, a large proportion of the avermectins administered to livestock pass unchanged out of the body in the feces. These residues remain in the dung pat for several weeks, to exert their toxic effects on a spectrum of dung-using insects, both harmful (e.g., various flies) and beneficial (e.g., dung beetles). The situation is particularly of concern in Australia where, as noted in Section 2.5, a range of exotic dung-beetle species have been introduced to deal with the massive amounts of dung produced by domestic cattle and sheep. Avermectins have been shown to exert a large number of detrimental effects on growth and reproduction of these beetles, though these

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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