Notes From Nelson

Biological control is the use of beneficial organisms to help control pest organisms. These beneficial organisms are often referred to as “biocontrol agents” or “natural enemies.” Weeds, pest insects, and plant diseases are some of the frequent targets of biological control in agriculture. Natural enemies can themselves be predatory/parasitic insects (targeting pest insects), herbivorous (plant-feeding) insects (targeting weeds), or diseases (pathogens) of pest insects, weeds, or even other harmful plant pathogens.

Classical biocontrol is the introduction of natural enemies from abroad, with the goal of long-term establishment. Many of our insect pests and problem weeds have been accidently introduced from other places. One of the reasons they become pests is that they arrive without their own natural enemies that help control them in their native range. By introducing the natural enemies of a given pest here, we re-establish the predator-prey relationship.

The introduction of biocontrol agents into the US is very strictly regulated by the Federal government, through the offices of the USDA. Detailed environmental assessments must be done before a permit is issued allowing domestic release of an organism. One of the goals of this environmental assessment is to determine what kind of impact the introduced organism would be likely to have on non-target (unintended) species and the environment. The required environmental assessments required for insect-targeting predatory/parasitic natural enemies used to be much less strict than that required for plant-feeding insects intended for weed biocontrol. That has changed a lot in recent years, with standards for the environmental assessment of predatory/parasitic insects becoming much higher.

One of the greatest concerns when contemplating the introduction of a foreign natural enemy is the impact that it will have on non-target species and the environment. An important component of whether an organism is suitable for release/attempted establishment is how host specific it is – how many prey species it can and will use. Generalists that attack a wide range of species are no longer considered suitable for release. The more species a predator attacks, the greater its ecological “footprint” is likely to be – not just in terms of which non-target species may be affected, but also in terms of the ripple effects that flow to associated species from those species being affected.

Many times when discussions are had about biocontrol agents and their effect on non-target species, the Asian Ladybeetle is brought into the discussion. The Asian Ladybeetle is a natural enemy of the soybean aphid. The Asian Ladybeetle is familiar to many homeowners in areas where soybeans are produced because these ladybeetles gather in great numbers and can become quite an annoyance to people. The Asian Ladybeetle is an example of a natural enemy that, even though it is quite beneficial in the context of soybean fields, would still never meet today's standards for release. The Asian Ladybeetle was NOT RELEASED in the US for biological control of the soybean aphid, but has in fact been in this country since at least the 1980's, having gotten here through a migratory process.