Classical biological control of insect pests of trees: facts and figures

Abstract

Classical biological control (CBC) is the introduction of a natural enemy of exotic origin to control a pest, usually also exotic, aiming at permanent control of the pest. CBC has been carried out widely over a variety of target organisms, but most commonly against insects, using parasitoids and predators and, occasionally, pathogens. Until 2010, 6158 introductions of parasitoids and predators were made against 588 insect pests, leading to the control of 172 pests. About 55% of these introductions were made against pests of woody plants. Establishment rates of natural enemies and success rates were higher in CBC projects targeting pests of woody plants than other pests. This review aims to answer the questions most commonly asked regarding CBC against insect pests, with particular emphasis on tree pests. The topics covered include, among others: variations in rates of successes among different systems, different target insect groups and different agents; temporal trends in CBC practices and successes; economic and environmental benefits; risks and ways to mitigate the risks; CBC against native pests; accidental successes through the adoption of the invasive pests by native natural enemies or accidentally introduced agents; and prospects and constraints for the practice of CBC in the future. Questions are answered based on the analysis of two databases, the BIOCAT2010 database of introductions of insect biological control agents for the CBC of insect pests, and a database of introductions of entomopathogens against insect pests.

Weevils as Targets for Biological Control, and the Importance of Taxonomy and Phylogeny for Efficacy and Biosafety

“…With reference to the BIOCAT database [18], as updated by Kenis, et al [19], 23 genera (approximately 38 species) of Curculionidae have been the subject of a classical biological control programme; of these 24 weevil species (63 %) have BCAs permanently established in at least one of the countries of release (Table A1 in Appendix A). Impact of BCAs on weevil hosts has ranged from complete control (no other control method required) to no impact at all on pest populations (Table A1).…”

Microbial Biopesticides in Agroecosystems

“…The basic concept of employing living organisms and natural products leverages the properties of natural ecosystem components to counteract the biotic and reproductive potential of pests. In agricultural ecosystems, the growth of harmful insect and other invertebrate populations is, in fact, favored by an oversimplification of living communities [2], so that biological control methods based on the use of natural enemies (i.e., predators and parasitoids) [3], and pest disease agents [4] may restore a lost ecological balance. Invertebrate pathogens are represented by several microbials, and in particular by bacteria, fungi, baculoviruses, and nematodes.…”

Understanding the Evolutionary Ecology of host–pathogen Interactions Provides Insights into the Outcomes of Insect Pest Biocontrol

“…Classical biocontrol refers to the control of pest species by the deliberate introduction of exotic or adapted natural enemies including pathogens, parasites, herbivores or predators [1]. However, just under a third of classical biocontrol attempts targeted at insect pests have been successful [2]. Many of these failures have been attributed to the low rate of establishment of introduced control agents [3][4][5], but cases where the control agent became established and yet failed to depress the targeted insect pest population are also common.…”