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Learn more about classical biocontrol

Several brown, slimy-looking larvae on a leaf of a lily plant that has been chewed up. A small black wasp that is less than a third of the size of the larva is perched on one of them.
A tiny wasp lays its eggs in the larvae of the invasive lily leaf beetle. Releasing these wasps in the northeastern U.S. is a form of classical biocontrol. Photo credit: Dan Gilrein

Last week, some colleagues told me about a cool online database that will help you learn more about how classical biocontrol is helping us fight invasive insects.

Classical biocontrol means introducing a natural enemy of a pest to help manage that pest. The natural enemy establishes a population where you have released it (and maybe even spreads), so that you don’t need to repeatedly release more natural enemies. It is a strategy that can be especially useful against invasive pests.

One thing that makes a pest invasive is the fact that when it arrives in a new place (for example, on a new continent), native organisms don’t eat it because they have not evolved with this new pest as a food source. Sometimes scientists can search the geographic area from which the invasive pest came and find a natural enemy of that pest. Many tests are done over a long period of time in order to assess potential unintended consequences of introducing this natural enemy to a new place. For example, scientists determine whether the new natural enemy is likely to also impact populations of native organisms (especially those that are not pests). Only after extensive study will this new natural enemy be released to help reduce populations of the invasive pest.

When done carefully, classical biocontrol can be a lower-risk solution to managing invasive pests compared to chemical pest management. It is also a long-term solution. The new natural enemy reproduces in its new geographic range and brings the invasive pest population into balance. The invasive species won’t be eliminated, but it will likely do less damage.

A new database from the University of Massachusetts lets you learn more about insects that have been introduced to North America to control invasive insect pests as classical biological control agents. You can Search the Catalog by the scientific name of the target pest, the scientific name of the natural enemy, information about where and when the natural enemy was first released, or other criteria.

Held against the background of a person's hand, you can see the underside of a hemlock branch. It looks like there are small tufts of white cotton where each needle attaches to the branch.
The invasive hemlock woolly adelgid on a hemlock branch. Several different classical biocontrol agents have been released in the U.S. to manage this invasive pest. Photo credit: Amara Dunn

You will need to know the scientific name of the pest or natural enemy you are interested in, but a quick Google search can help you with that. For example, Adelges tsugae is the hemlock woolly adelgid, which you may have heard about. If not, you can learn more here. Laricobius nigrinus was released to help manage hemlock woolly adelgid. Other examples include Agrilus planipennis (emerald ash borer) and Lilioceris lilii (lily leaf beetle). NYS IPM is involved in a project to use classical biocontrol to manage this last pest in NY.

As the days start to get shorter and cooler, you might find yourself spending more time indoors. And if that’s the case, why not spend some time learning more about how classical biocontrol is helping to manage pests in the landscapes around you?

Biocontrols, biopesticides, biostimulants, oh my!

There are a lot of different “biological” products on the market. Frankly, the terms used to describe them can be a little confusing. So let’s take a closer look at a few terms and exactly what they mean.

First, what is a pesticide? According to the Cornell Pesticide Management Education Program, “a pesticide is any substance or mixture of substances used to kill pests or to prevent or reduce the damage pests cause”. Pesticides include repellents, but exclude traps (if they are only mechanical or physical). The important point is that pesticides are defined by their purpose, not by their ingredients. Pesticides may be chemicals, plant extracts, or microorganisms, but their purpose is to prevent pest damage. Pesticides are regulated by the Environmental Protection Agency (EPA), and must always be used according to their labels.

Bacteria producing a compound that inhibits fungal growth
The bacteria at the bottom of this plate (shiny streaks) produces a compound that inhibits the growth of the fungus (white and fuzzy) at the top of the plate. Image courtesy of Dr. Carly Summers

“Biopesticide” is a term defined by the EPA as “certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals.” All biopesticides are pesticides, and must be handled and applied as such. They fall into one of three groups:

  • Microbial – active ingredient is a living microorganism (fungi, bacteria, viruses, protozoa) or a product made by a microorganism
  • Biochemical – natural compounds including both plant extracts and naturally-occurring chemicals
  • Plant-incorporated protectants – the products that result from inserting new genes into plants (i.e., the result of genetic engineering)

Biopesticides control pests or prevent pest damage in four ways:

  1. Consuming or parasitizing the pest, directly – An example of this is a beneficial fungus that eats a pest fungus, or a beneficial fungus that infects and kills a pest insect.
  2. Poisoning the pest – Some microorganisms produce antibiotics that are toxic to pests. There are numerous bacteria that do this.
  3. Crowd out the pest – Pest microorganisms (pathogens) can’t colonize and invade a plant if the surface of the plant (leaves, roots, etc.) are already covered with beneficial microorganisms. There just isn’t space.
  4. Stimulating plant defenses – Although very different from human immune systems, plants do practice self-defense. Beneficial microorganisms can cause plants to “turn on” their defenses before they encounter a pest. The plant is then less likely to be damaged by the pest.

Sometimes a single biopesticide functions in more than one of the above ways. But, again, the purpose of using a biopesticide is to control a pest. Biostimulants have a different primary purpose: enhancing plant health (which can lead to the plant being less susceptible to attack by a pest). The European Biostimulants Industry Council has defined a biostimulant as “containing substance(s) and/or microorganisms [e.g., bacteria and fungi] whose function when applied to plants or the rhizosphere [soil surrounding plant roots] is to stimulate natural processes to enhance/benefit nutrient uptake, nutrient efficiency, tolerance to abiotic [non-biological] stress, and crop quality.” This definition is also supported by the Biological Products Industry Alliance. No regulatory definition of biostimulant currently exists in the United States. Biostimulants are registered either as fertilizers or as biopesticides, depending on the claims (pest control vs. plant health enhancement) made by the registrant.

Biostimulants can include a wide variety of ingredients, which can be placed in the following four categories:

  • Microorganisms (e.g., fungi and bacteria)
  • Extracts from plants or seaweed
  • Organic (i.e., carbon-containing) molecules including various components of soil organic matter
  • Inorganic (i.e., not carbon-containing) elements or molecules

Biostimulants can enhance plant health in multiple ways. In some cases, scientists don’t yet know how a biostimulant enhances plant health, just that it does. Like biopesticides, a biostimulant may have more than one of the following modes of action:

  1. Improve soil quality by impacting soil characteristics like water holding capacity, structure, or aeration
  2. Improve plant access to nutrients already present in the soil
  3. Stimulate plant defenses or otherwise increase the plant’s tolerance to stress (from biological or non-biological sources)
  4. Improve root growth of the plant (so that the plant can take up nutrients better)
  5. Improve the quality of something produced from or by the plant (e.g., improved flavor or nutrition of fruit)
Venn diagram showing the relationships among biocontrol, biopesticides, and biostimulants. Biocontrol is when an organism controls pests. Often that organism is an insect (and similar, like spiders or predatory mites), a nematode (tiny worm), or a microorganism or microbe (bacteria, fungi, and viruses). Insects and nematodes that control pests are biocontrol, but are not regulated as pesticides. Microbes that control pests are regulated as pesticides. Along with plant extracts, pheromones, naturally-occurring biochemicals, and plant-incorporated protectants (found in GMOs) they are biopesticides. Biostimulants may be microbes, extracts from plants or seaweed, or natural compounds. But their purpose is to improve plant health and/or quality; not to control pests. The EPA is currently reviewing the definition of the term “biostimulant” and there may be more regulation on these products in the future.
Biocontrol, biopesticide, biostimulant – these terms can get confusing. This diagram is my attempt to show how the terms are related to each other.

And where does biocontrol fit in? In several places on this blog, I have noted that definitions of biocontrol vary. I think most scientists who study biocontrol would agree that a living microorganism that is applied to the soil or to a plant and that consumes or parasitizes a pest (a type of biopesticide) is a biocontrol agent. But there are lots of gray areas. What if the biopesticide contains only products of the microorganism which are antagonistic to the pest, and no living organisms? If a microbial biostimulant enables a plant to more efficiently take up nutrients, making the plant more tolerant of stress (whether from an abiotic source like drought, or a biotic source like a pathogen that causes disease) is that still biocontrol?

These are debates I’d rather not spend a lot of time on (at least on this blog). Suffice it to say that at least some biopesticides and at least some biostimulants are also considered types of biocontrol. There are a lot of biological products available to you. Exactly how each is classified (biostimulant versus biopesticide) makes a difference in how the product can be legally used. Know what you are using and why. And always, always, always read and follow the label!

An introduction to biocontrol

Adult ladybugs are a commonly-recognized biocontrol agent, but there’s so much more to biocontrol!

Biocontrol can be an important part of an integrated pest management strategy (learn more about “IPM in a Nutshell”). For example, biocontrol organisms that support plant health can make them less susceptible to the pests that damage them (prevention). If something needs to be applied to reduce pest populations (or keep them low), biocontrol products tend to be less harmful to other critters or people than chemical pesticides (choosing a pest management strategy with low environmental impact).

In the images at the top of this blog, you can see some examples of biocontrol. From left to right…

Syrphid flies are often seen foraging for pollen and nectar on flowers, but immature syrphid flies (larvae; not pictured) also eat pest insects. (Photo credit: Ken Wise)

Some bacteria produce compounds that slow the growth of pest fungi, or even kill them. (Photo credit: Carly Summers)

Many different species of parasitic wasps use their stingers to lay eggs inside pest insects (which is what happened to this aphid). The egg hatches, and the developing wasp eats the pest from the inside out, eventually leaving through the exit hole seen in this picture. (Photo credit: Ken Wise)

Some stink bugs are pests, while other stink bugs (like this one) are predators of pests. (Photo credit: Ken Wise)

Adult ladybugs are more easily-recognized than immature ladybugs (larvae), like the one that is eating aphids in this picture. (Photo credit: Ken Wise)

In the background is a picture taken under the microscope of nematodes (tiny worms). Some nematode species seek out and enter soil-dwelling pest insects, carrying bacteria that will kill the insect. (Photo credit: Maxwell Helmberger)

Posts on this blog will explain how biocontrol is already contributing to IPM in New York, and how its use in pest management could be improved. The information is posted by Amara Dunn, Biocontrol Specialist with the New York State Integrated Pest Management Program. If you have questions about biocontrol, you can contact Amara by email (, call her office (315-787-2206), or leave a comment on this blog.