Insects And Humans

effects can be significantly lessened by careful selection of the times when livestock are 749

treated (i.e., when the dung beetles are less active). However, the adoption of a sustained-release bolus for delivery of the avermectins in livestock may have a major influence on dung-beetle populations (Strong, 1992; Herd etal., 1993).

Spinosyns, discovered in the late 1980s, are produced by another actinomycete, Sac-charopolyspora spinosa. Like avermectins, spinosyns are easily degraded by ultraviolet light and soil microorganisms. They have low toxicity to mammals, birds, and non-target (beneficial) insects. Commercial preparations are available for control of a range of pests on cotton, vegetables, turf, and ornamentals (Crouse and Sparks, 1998).

Azadirachtin is the major component of the oil extractable from the seeds and leaves of the neem (margosa) tree (Azadirachta indica), an evergreen endemic to southern and southeastern Asia, but now found also in Africa, the United States, and Australia. It has been shown to exert a variety of potentially useful effects including inhibition of settling, oviposition, and feeding behaviors, interference with both embryonic and postembryonic development, reduction in number of eggs matured, and mortality, and it is effective on a wide range of pest insects, especially phytophagous species. Because azadirachtin is primarily a feeding poison for juvenile phytophagous insects, it shows great selectivity in the sense that the pests' natural enemies (adult parasitoids and predators) are unaffected by it. It is also relatively non-toxic to vertebrates. Offsetting these advantages are its limited persistence in the field, its slow-acting nature, and, of course, the potential for the development of resistance. Nevertheless, it may become a useful adjunct to already available pesticides in underdeveloped countries, and a few commercial preparations are available (Schmutterer, 1990; Isman et al., 1991; Gahukar, 1995; Beckage, in Rechcigl and Rechcigl, 2000).

Three major problems have arisen as a result of the massive use of insecticides over the past 70 years. First, many insects and mites have developed resistance to one or more of the chemicals (Tables 24.4 and 24.5). (See Chapter 16, Section 5.5 for a discussion

TABLE 24.4. Number of Species of Insects and Mites in Which Resistance to One or More Chemicals Has Been Documented"

Year

Species

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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