Insects And Humans

inorganics include fluoride salts (developed at about the end of the 19th century, follow- 747

ing the realization that toxic residues were left by arsenicals), sulfur, borax, phosphorus, mercury salts, and tartar. These inorganic insecticides were typically sprayed on the pest's food plant or mixed with suitable bait. In other words, all are "stomach poisons" that require ingestion and absorption to be effective. Thus, they were unsatisfactory pesticides for sucking insects for which "contact poisons," absorbed through the integument or tracheal system, are necessary.

The "botanicals" are organic contact poisons produced by certain plants in which they serve as protectants against insects (Chapter 23, Section 3.1). Among the earliest to be used were (1) nicotine alkaloids, derived from certain species of Nicotiana, including N. tabaca (tobacco) (family Solanaceae); (2) rotenoids extracted from the roots of derris (Derris spp.) and cube (Lonchocarpus spp.); and (3) pyrethroids, produced by plants in the genus Pyrethrum (Chrysanthemum) (family Compositae).

Because of their high mammalian toxicity, nicotine has been completely superseded by synthetics, while rotenone use is now mainly restricted to control of some sucking pests on crops and pests of pets and livestock. The pyrethroids, when first available commercially, were an important group of insecticides for use in the home, as livestock sprays, and against stored-product, vegetable, or fruit pests, primarily because of their low toxicity to mammals. Initially, a major disadvantage of pyrethroids was their photolabile nature (instability in light) and the need, therefore, to reapply them frequently made them expensive to use. Thus, they were largely replaced by cheaper, synthetic insecticides in the 1940s, an important consequence of which was that relatively few insects became resistant to them. This feature, in conjunction with the development of several photostable synthetic pyrethroids (e.g., cypermethrin, permethrin, fenvalerate, and deltamethrin), has led to a resurgence in the importance of these compounds which now account for about one third of world insecticide use (Elliott et al., 1978; Leahy, 1985; Pickett, 1988). Unfortunately, but not surprisingly, paralleling this increased usage has been a major increase in arthropod resistance to pyrethroids, from fewer than 10 species in 1970 to over 80 in 2003 (Metcalf, 1989; GeorghiouandLagunes-Tejeda, 1991; Resistant Arthropod Database, 2004).

Though two synthetic organic insecticides had been commercially available prior to 1939 (dinitrophenols in Germany, first used in 1892; organic thiocyanates in the United States from 1932 on), it is generally acknowledged that this is the year in which the synthetic organic insecticide industry took off. After several years of research for a better mothproofing compound, Müller, who worked for Geigy AG in Switzerland, discovered the value of DDT as an insecticide. In the next few years, production of DDT began at the company's plants in the United Kingdom and United States, although because of the Second World War, knowledge of DDT was kept a closely guarded secret. In early 1944, DDT was first used on a large scale, in a delousing program in Naples where typhus had recently broken out. Some 1.3 million civilians were treated with DDT, and within 3 weeks the epidemic was controlled (Fronk, in Pfadt, 1985). Later that year the identity of the "miracle cure" was revealed, and the world soon became convinced that with DDT (and other recently developed insecticides) pest insects would become a thing of the past. In 1948 Müller was awarded a Nobel Prize, though, interestingly, the first example of insect resistance to DDT had been reported 2 years earlier!

Through the 1940s and into the 1960s, much research was carried out in Western Europe and the United States for other insecticides as effective as DDT. Initially, the search focused on other chlorinated hydrocarbons, including lindane, chlordane, aldrin, dieldrin, endrin,

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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