Much of the current focus on leafy spurge biocontrol is redistributing various flea beetles in the genus Aphthona to provide control of leafy spurge in a variety of habitats, soil types, and climates.
In contrast with the successful biological control programs, no insect became established for six target weeds. For five of these six target weeds where no insects became established, only a single importation was conducted with insects distributed at most to two sites. The only exception was a slightly more intense attempt to establish a single insect against puncture vine, Tribulus terrestris L., where the curculionid, Microlarinus lareynii (Jacquelin du Val), was released in multiple states with a concerted effort to select for a cold-adapted strain for release in the north temperate zone. All attempts to establish M. lareynii in the north temperate zone, which has a severe winter, failed.
There is no compelling evidence to suggest that the success of classical biological control is less in cool temperate regions. Indeed, even if there were such evidence, it would imply only that we would have to try harder for successful biological control. A lower probability of success does not imply that biological control should not be attempted.
Our retrospective analysis of classical biological control of arthropods and weeds revealed considerable variation in the meaning of successful establishment and successful control. We suggest that biological control practitioners analyze this variation and more rigorously evaluate success. To facilitate this discussion, we propose conceptual frameworks to compare and contrast these meanings and operationalize them with potential observations. We found that our frameworks could be applied to the historic literature on biological control in cool temperate regions, but the data are too few to allow any reasonable generalizations.
The potential for research on biological control in cool temperate regions seems vast. There are many unresolved cases of classical biological control, such as brown- tailed moth, that could yield interesting insights. There are several ongoing efforts to introduce natural enemies that could be enhanced. Inundative methods are just now being developed for control of arthropod pests, weeds, and pathogens, and conservation of natural enemies has been limited by our knowledge of the ecology of the natural enemies. Integration of biological and chemical control in integrated pest management systems has remained elusive. Research to develop adaptive decision-making plans could accelerate integration and alleviate much unnecessary research to develop precise estimates of the effects of partial and occasional biological controls.
Andow, D. A., G. C. Klacan, D. Bach, and T. C. Leahy. 1995. "Limitations of Trichogramma nubilale (Hymenoptera: Trichogrammatidae) as an inundative biological control of Ostrinia nubilalis (Lepidoptera: Crambidae)". Environmental Entomology 24:1352-57.