Insects And Humans

Among the best-known examples of an introduced plant pest are the prickly pear cacti 729

(Opuntia spp.) taken into Australia as ornamental plants by early settlers. Once established, the plants spread rapidly so that by 1925 some 60 million acres of land were infested, mostly in Queensland and New South Wales. Surveys in both North and South America, where Opuntia spp. are endemic, revealed about 150 species of cactus-eating insects, of which about 50 were judged to have biological control potential and were subsequently sent to Australia for culture and trials. Larvae of one species, Cactoblastis cactorum, a moth, brought from Argentina in January, 1925, proved to have the required qualities and within 10 years had virtually destroyed the cacti (Figure 24.1). Perhaps the most remarkable feature of this success story is that only 2750 Cactoblastis larvae were brought to Australia, of which only 1070 became adults. From these, however, more than 100,000 eggs were produced, and in February-March of 1926 more than 2.2 million eggs were released in the field! Additional releases, and redistribution of almost 400 million field-produced eggs until the end of 1929, ensured the project's success.

The classical example of an insect pest brought under biological control is the cottony-cushion scale, Icerya purchasi, which was introduced into California, probably from Australia, in the l860s. Within 20 years, the scale had virtually destroyed the recently established, citrus-fruit industry in southern California. As a result of correspondence between American and Australian entomologists and of a visit to Australia by an American entomologist, Albert Koebele, two insect species were introduced into the United States as biological control agents for the scale. The first, in 1887, was Cryptochaetum iceryae, a parasitic fly, about which little is heard, though DeBach and Rosen (1991) consider that it had excellent potential for control of the scale had it alone been imported. However, the abilities of this species appear to have been largely ignored with the discovery by Koebele of the vedalia beetle, Rodolia cardinalis, feeding on the scale. In total, only 514 vedalia were brought into the United States, between November 1888 and March 1889, to be cultured on caged trees infested with scale. By the end of July 1889, the vedalia had reproduced to such an extent that one orchardist, on whose trees about 150 of the imported beetles had been placed for culture, reported having distributed 63,000 of their descendants since June 1! By 1890, the scale was virtually wiped out. Similar successes in controlling scale by means of vedalia or Cryptochaetum have been reported from more than 60 countries (Hokkanen, in Pimentel, 1991, Vol. 2).

A third example of an introduced pest being brought under control by biological agents is the winter moth, Operophtera brumata, which, though endemic to Europe and parts of Asia, was accidentally introduced into Nova Scotia in the 1930s. Its initial colonization was slow, and it did not reach economically significant proportions until the early 1950s, and by 1962 it had spread to Prince Edward Island and New Brunswick. The larvae of the winter moth feed on the foliage of hardwoods such as oak and apple. Though more than 60 parasites of the winter moth are known in western Europe, only 6 of these were considered to be potential control agents and introduced into eastern Canada between 1955 and 1960. Two of these, Cyzenis albicans, atachinid, and Agrypon flaveolatum, an ichneumonid, became established, but between them they brought the moth under control by 1963. Embree (in Huffaker, 1971) noted that the two parasites are both compatible and supplementary to each other. When the density of moth larvae is high, C. albicans, which is attracted to, and lays its eggs near, feeding damage caused by the larvae, is a more efficient parasite than A. flaveolatum. However, once in the vicinity of damage, it does not specifically seek out winter moth larvae. Thus, at lower density, it wastes eggs on non-susceptible defoliators such as caterpillars of the fall cankerworm, Alsophila pometaria. Hence, at low host

FIGURE 24.1. (A) Cactoblastis cactorum caterpillars feeding on cactus pad; and cactus-infested pasture before (B) and after (C) release of Cactoblastis. [From D. F. Waterhouse, 1991, Insects and humans in Australia, in: The Insects of Australia, 2nd ed., Vol. 1 (CSIRO, ed.), Melbourne University Press. By permission of the Division of Entomology, CSIRO.]

FIGURE 24.1. (A) Cactoblastis cactorum caterpillars feeding on cactus pad; and cactus-infested pasture before (B) and after (C) release of Cactoblastis. [From D. F. Waterhouse, 1991, Insects and humans in Australia, in: The Insects of Australia, 2nd ed., Vol. 1 (CSIRO, ed.), Melbourne University Press. By permission of the Division of Entomology, CSIRO.]

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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