Approaches of Biological Control: Importation

Importation biological control means to introduce a new natural enemy from one locale to a new setting, hence "importing" it. This approach is often called "classical" biological control; some biological control practitioners consider this the only "true" biological control approach. There are many examples of successful imporation projects; for example, the often-cited (maybe over-cited) Vedalia beetle project against cottony cushion scale from the late 1880s through the present led to the increase in use of biological control worldwide. (Caltagirone and Doutt 1989). Several detailed accounts of many importation projects are available (see Debach and Rosen 1991, Van Driesche and Bellows 1996, Bellows and Fisher 1999).

Although most entomologists are familiar with the Vedalia story, other importation projects have been equally successful. Several parasitic wasps, such as the ichneumonids Microctonus aethiopoides and two species of Bathyplectes were imported from Europe and used against alfalfa weevil (Hypera postica) in North America. The project was estimated to cost approximately $1 million, but returned annual benefits of over $8 million per year by the late 1960s. Another project against an alfalfa pest, the alfalfa blotch leafminer fly (Agromyza frontella) was brought under control by release of several parasitic wasps from Europe (e.g., the braconid Dacnusa dryas and the eulophid Chrysocharis punctifacies), was estimated to have saved $13 million per year (1983 estimate) (Drea and Hendrickson 1986). This project was interesting, as biological control was seen as the only alterative to this pest -- two other alfalfa pests (alfalfa weevil and pea aphid) were already under biological control, which could be disrupted by intervention with pesticides. This project also will be interesting in the near future, as the pest has moved into the Midwestern U.S. without the introduced parasites. Whether re-introduction or movement of the parasites into the Midwest will prove successful will have to be determined.

Another importation project that is interesting for different reasons is that of the success against cassava mealybug (Phenacoccus manihoti) throughout sub-Saharan Africa. The pest, accidentally introduced from South America, was brought under control through importation of an encyrtid parasite from South America, Epidinocarsis lopezi. Within a few years of the initial release in Nigeria, the parasite was released extensively -- and successfully -- throughout Africa. The leader of that project, Dr. Hans Herren (then of the International Institute for Tropical Agriculture), won the World Food Prize in 1995 for his role in this successful project that helped assure food security for hundreds of millions of people (Neuenschwander and Herren 1988).