HPIPM:Disadvantages/Advantages

Author: David J. Kazmer & Michael J. Brewer

Advantages and Disadvantages of Biocontrol

Pest Management Aspects: Biocontrol reduces, but does not eradicate, pest populations. Thus, the success of a biocontrol program will depend on level of suppression attained and the tolerable level or economic threshold of the pest. Tolerance levels for some pests, such as direct pests that feed on or in the harvested product (e.g., stored grain), are very low and the likelihood of attaining sufficiently low suppression with biocontrol alone is comparatively low. Success is more likely for pests with higher tolerance levels, such as indirect pests that may defoliate plants or feed on sap but not significantly impact yields except at very high densities.

When successful, classical biocontrol provides self-sustaining, broad-scale control of the target pest. This is in sharp contrast to chemical control and augmentation biocontrol which typically require repeated treatment and provide control only at or near the site of application. Offsetting these advantages of classical biocontrol are low success rates (about two-thirds of all projects fail to provide substantial or complete control) and extended periods before widespread control is attained (several-to-many years).

Most natural enemies used in biocontrol attack a very limited number of species. Thus, instances where a specific biocontrol practice interferes with other, ongoing pest control practices are relatively rare. In contrast, chemical control practices often interfere with biocontrol because of the broad-spectrum effects of many pesticides. This makes it difficult to integrate biocontrol practices into pest management systems that rely heavily on pesticides.

Economics: One study has estimated that successful classical biocontrol programs return $32 in benefits for each $1 invested in developing and implementing the program (i.e., a 32:1 benefit-to-cost ratio). When unsuccessful as well as successful programs are taken into account, the average benefit-to-cost ratio is still in the very favorable range of 11:1. The same study estimated benefit-to-cost ratios for chemical control programs to be about 2.5:1. The greater economic returns from classical biocontrol are due to the self-sustaining control it provides and the absence of recurring treatment costs. Classical biocontrol programs are also usually publically-funded, so direct, out-of-pocket costs to individuals are small.

Augmentation and some conservation biocontrol programs do have recurring treatment costs. Whether or not these costs are more or less favorable than chemical control costs depends on many factors including the particular natural enemies and chemicals involved, and the relative levels of pest suppression or yield increase attained with each method.

Environment: Incorporation of biocontrol practices into pest management systems can result in reduced pesticide usage. This will obviously reduce exposure to the legal, environmental, and public safety hazards of pesticides.

Biocontrol was once viewed as an entirely safe technique to the environment. However, the environmental safety of biocontrol is being called into question by some conservation biologists. These individuals fear that some introduced natural enemies pose significant threats to native species, especially threatened and endangered species. In response to this concern, state and federal processes guiding the importation and release of exotic natural enemies have been or are being revised.