How to combine the powers of biological control agents and pesticides

Growers using biocontrol, whether through micro- or macro-biocontrol agents (BCAs), quickly learn three key lessons.

First, biocontrol is hard. We can’t simply buy BCAs when we need them, put them on the plants and walk away. Success requires proactive planning throughout the entire crop cycle, as well as consistent scouting. BCAs are living organisms with their own behaviors, which can make their efficacy unpredictable.

Second, there is no one-size-fits-all biocontrol program. Every program must be customized to meet each operation’s unique environments and management goals. Third — and the focus of this article — biocontrol doesn’t eliminate the need for pesticides.

It’s understandable that those invested in biocontrol are cautious about pesticide use.

Pesticides are developed to kill or inhibit insects, mites and microorganisms. Ironically, BCAs are also insects, mites and microorganisms. Pesticide use inevitably impacts BCA biology and behavior; therefore, eliminating pesticide use serves to protect investments in biocontrol.

Despite the concerns, an integrated program can achieve more effective pest management. Integration may be the only available approach when biocontrol programs achieve poor or mediocre performance, or when we are dealing with a pest or disease that has no effective biocontrol solutions or is too expensive to manage biologically.

Two paths to integration

There are generally two main ways to integrate pesticides with biocontrol:

Use compatible pesticides: those that have minimal effects on the biology and behavior of your BCAs.

Separate BCAs and pesticides by space or time: applying them at different times or in different areas of the crop. These two approaches are not mutually exclusive and can be used together.

Understanding compatibility

Pesticide compatibility refers to both direct and indirect effects on BCAs.

Direct effects involve immediate BCA mortality from direct application of or exposure to fresh or aged residues.

Indirect effects, also known as sublethal or chronic effects, impact BCA behavior and biology — such as feeding, reproduction or lifespan — but may take time to become apparent.

In a perfect world, we should know both direct and indirect effects when developing tactics for integrating biocontrol and pesticides. In reality, we only have incomplete information because research on indirect effects receives little attention. Direct effects are typically what most folks mean when discussing compatibility. So, how do you find compatibility information?

You may find a listing of incompatible or compatible products in product labels. For example, Camelot® O (copper octanoate) is highly effective against many diseases, but it can be mixed with the entomopathogenic bacterium Bacillus thuringiensis (Bt), according to the product label. This compatibility allows you to use Camelot O to control bacterial leaf spots while being assured that it will not affect the control of caterpillars with Bt.

Many BCA and pesticide suppliers provide compatibility charts or databases. Good examples include:

• • SePRO’s Insecticides for CEA Crop Guide
• • Koppert’s Side Effects App
• • BioBest’s Side Effects Database

It is important to understand what toxicity/compatibility classification in these resources means and how it’s relevant to your decisions. In general, select pesticides that have the lowest toxicity classes for the BCAs you are using when pesticide treatments are needed.

Real-world examples

At SePRO, we often help growers evaluate real-world compatibility. For example:

Obtego® Fungicide and Plant Biostimulant can be used alongside Junction (copper hydroxide + mancozeb), even though it may seem risky due to Obtego being live Trichoderma species.

Talus® (buprofezin), an insect growth regulator, has little to no impact on adult BCAs and only slight effects (i.e., less than 50% mortality) on nymphs of some beneficial insects. It’s a great fit for whitefly biocontrol in poinsettias.

Timing and targeted applications

An alternative approach to integrating biocontrol and pesticides, even for incompatible pesticides, is to prevent contact between BCAs and pesticides by using them at different times or places. While it requires careful planning, this approach provides you with the greatest flexibility in using pesticides for specific situations, such as reducing pest population before BCA release or dealing with pest species that do not have effective biosolutions.

You can apply BCAs at a certain time after pesticide application because the pesticide residue has degraded sufficiently to have minimal impacts. For example, you can apply Obtego Fungicide and Plant Biostimulant three days after the application of incompatible fungicides, such as those containing mancozeb, propiconazole, tebuconazole and triflumizole.

While Talus has no impact on adult predatory midges, it may slightly reduce the survival of larvae for one week. Similarly, Talus has no impact on many predatory mite species, except Phytoseiulus persimilis, which may have slightly increased mortality for about three days. Knowing this, you can plan to release or reintroduce predatory midges or P. persimilis one week after a Talus application. You should contact your propagators to inquire if and when they use pesticides on stock plants so you can determine when to release BCAs.

Impacts of pesticides can also be minimized by using BCAs and pesticides on different parts of a crop. This can be done by spot treatments, i.e., applying pesticides only to areas where pests are found. Mobile BCAs will recolonize the treated areas after the harmful period has passed.

Alternatively, apply pesticides and BCAs to different parts of the plants, such as using a compatible pesticide on the canopy to minimize impacts on BCAs and using a less compatible pesticide in the media where the BCAs likely will not venture to.

Some incompatible pesticides can be used in surprising ways. For example, Akari® (fenpyroximate), a miticide, has minimal impact on most BCAs but is highly detrimental to predatory mites for about one week after application. You may use Akari to knock down a spider mite population, then release predatory mites after a week. Some growers also use Akari to eliminate predatory mites before shipping so that shipment is not stopped by inspectors or refused by customers who cannot tell the predatory mites from pest mites.

Integrating biocontrol and pesticides requires careful planning and an understanding of the properties and limitations of both actors. With the right strategy, you can take advantage of both worlds to improve pest management outcomes. Let us help you develop an integrated program that works for your unique operation.

JC Chong, Ph.D., is the technical development manager for ornamentals at SePRO Corporation. sepro.com