The potential of entomophagous parasites for pest control

Abstract

The perspective of the use of hymenopterous parasites for pest control is discussed. First, the planning of a biological control project is given, together with a description of the disagreement which exists about the necessity and predictive value of studies conducted prior to the introduction of a natural enemy. Although several contributing factors of parasites to the depression of pest numbers have been identified, the practical value of extensive pre-introductory research is still limited. Parasites have been used successfully against a large variety of pests occurring in completely different cropping systems and in all major climates. Success seems largely to have been the result of the amount of research directed to the solution of a pest problem. The ratio of successes obtained with parasites compared to those achieved with predators and pathogens is 82:17:1, respectively. The rate of success after introduction is high for natural enemies (± 6%) when compared with that for chemicals (± 0.1–0.05% of the tested chemicals is marketable). Data on economic aspects are also positive for biological control programs. The risks of using parasites for pest control are minimal, especially when compared with chemical pesticide use. In the second part of the article an example is presented of the recent development of biological control programs for pest control in greenhouses, an expensive cropping system in which growers will not risk damage from pests. During a 15-year period, biological control programs for six major pests were developed and several species of natural enemies became commercially available; this success was partly the result of good cooperation between several working groups of the International Organisation for Biological Control (I.O.B.C.), mainly in Western Europe. The causes that limit the application of biological control are also discussed. The article is concluded with optimism: many effective natural enemies await discovery, and the development of biological control programs deserves more effort.