Insects And Humans

densities, A. flaveolatum is more effective because it oviposits specifically on winter moth 731


The three examples described above indicate one method whereby the importance of biological control can be demonstrated, namely, by introduction of potential pests into areas where natural regulators are absent. Another way of demonstrating the same phenomenon is to destroy the natural regulators in the original habitat, which enables potential pests to undergo a population explosion. This has been achieved frequently through the use of non-selective insecticides. For example, the use of DDT against the codling moth, Cydia pomonella, in the walnut orchards of California, led to outbreaks of native frosted scale, Lecanium pruinosum, which was unaffected by DDT, whereas its main predator, an en-cyrtid, Metaphycus californicus, suffered high mortality (Hagen et al., in Huffaker, 1971). Another Lecanium scale, L. coryli, introduced from Europe in the 1600s, is a potentially serious pest of apple orchards in Nova Scotia but is normally regulated by various natural parasitoids (especially the chalcidoids Blastothrix sericea and Coccophagus sp.) and predators (especially mirid bugs). Experimentally it was clearly demonstrated in the 1960s that application of DDT destroyed a large proportion of the Blastothrix and mirid population, and this was followed in the next two years by medium to heavy scale infestations. Recovery of the parasite and predators was rapid, however, and by the third year after spraying the scale population density had been reduced to its original value (MacPhee and MacLellan, in Huffaker, 1971).

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.

Get My Free Ebook

Post a comment