Abstract
Abstract The density of phytophagous insect pest populations is related (directly and indirectly) to several groups of factors that can be broadly divided into: abiotic, biotic and anthropogenic. Each extreme in the abiotic environment at a macro-level leads to a series of consecutive extremes in the biotic environment, which eventually results in micro-level responses in the individual organisms. The manifestation of factors acts in aggregate or in a sequence, creating a chain of processes around us. Insects very efficiently use the abundance of nutritional resources, resulting in a tremendous increase in their population density, and triggering control mechanisms through the emergence of parasitic and pathogenic infections (viruses, bacteria, fungi, microsporidia, protozoa and nematodes). The development of entomopathogenic infections in host populations is directly dependent on the characteristics of both the antagonist and the insect. It is associated with the lifestyle and life cycle of the insect, with features encoded in the mechanism of pathogen action, and limited by the pathogen’s virulence and pathogenicity.
Highlights
Among animals, insects are the most numerous taxonomic group
This review presents pathogen groups causing infection and parasite deseases in different forest and other insect pests in the context of extreme environmental conditions, cascade effect of the factors and epizootic which can results as natural mechanisms of insect regulation
A release of two microsporidian species Vairimorpha disparis Timofejeva and Nosema lymantriae Weiser isolated from Bulgaria was conducted in 2007 and 2008 in two Bulgarian gypsy moth populations and it was shown that N. lymantriae persisted in the test population within three years (Pilarska et al 2010)
Summary
Insects are the most numerous taxonomic group. They have occupied almost every ecological niche on the Earth and, studies of their ecological strategies, and of control mechanisms is becoming increasingly important (Leibhold 2012). The study of impacts of these factors on forest communities condition, which are habitats of various group of insects, is a major task for scientists. Disease-causing agents are involved in the regulation of insect populations, and include viruses, bacteria, protozoans, microsporidia, fungi, and nematodes. This review presents pathogen groups causing infection and parasite deseases in different forest and other insect pests in the context of extreme environmental conditions, cascade effect of the factors (abiotic, biotic and anthropogenic) and epizootic which can results as natural mechanisms of insect regulation
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