Biological Pest Control Starts With Accounting For Pesticide Compatibility

The beneficial parasitoid Encarsia formosa feeding on greenhouse whitefly
The beneficial parasitoid Encarsia formosa feeding on greenhouse whitefly.

More and more operations are using biological control against some of the toughest insect and mite pests. The driving force behind the trend is the need to combat difficult-to-control pest problems in order to produce sellable products.

The decision to reduce or eliminate the use of neonicotinoids and other pesticides also increases the appeal of biological control as a viable solution for pests, particularly aphids, whiteflies, and mealybugs.

Growers who endeavor to start a biological control program learn quickly that there is no cookie-cutter approach to success. Each program varies, depending on the pest, pest pressure, plants and cultivars, microclimates, and production practices. The combination of various factors sometimes necessitates individualized programs for different greenhouses in the same operation.

Single Out The Best Quality Biologicals For The Job

As with any other pest management program, all biological control programs start with proper pest identification, determination of pest pressure, and recognition of your tolerance level for the infestation and damage. Understanding the microclimates, and the production practices that create the microclimates, is also important. The combination of pest identification and production specifications help you communicate with suppliers and select the best biological control agents for the job.

Watch for quality of the beneficials and contact the supplier immediately if the beneficials did not survive well or behave abnormally upon arrival. It pays to use suppliers who are willing to work with you and guide you through the process. It is likely that you will have to work with several suppliers to develop a comprehensive biological control program that incorporates different products. It is also probable that you will have to make several changes, or have many thoughts of giving up, before settling on a tried-and-true approach, so be flexible and patient.

Many operations that use biological controls preventively have been successful in producing quality products while maintaining low chemical inputs. When an outbreak occurs, either because a pest species cannot be controlled by the existing biological control program or the pest pressure is too high for beneficials to control effectively, a grower may have to fall back onto conventional pesticides. A grower may also need pesticide applications if he or she wants to reduce pest density before releasing or applying beneficials.

Limit Beneficials’ Exposure To Non-Compatible Pesticides

Pesticides are created to kill or suppress living organisms, be it an insect, mite, fungus, weed, nematode, or beneficial bug. They can have direct and indirect effects on beneficials. Direct effects include acute or residual toxicity or mortality when the beneficials are exposed to a lethal dose, or longer-term reduction in efficiency, fecundity, foraging behavior, or progeny survival when the beneficials are exposed to a sublethal residue on the plant surface or in the consumed host or prey.

Direct effects are of greater concern to the practitioners of biological control in floriculture. In the case of managing two-spotted spider mite, the concerns are usually expressed as:
• Can I apply Sultan (as an example) to control two-spotted spider mite without ruining my Phytoseiulus persimilis program?
• I use Amblyseius swirskii to control western flower thrips, but I found an infestation of two-spotted spider mite. Can I use Sultan to control the two-spotted spider mite without impacting A. swirskii?
• Can I use Sultan to reduce two-spotted spider mite density before releasing P. persimilis?; If I am going to use Sultan, how long do I have to wait before I can safely release P. persimilis or A. swirskii again?

Keep Up-To-Date On Ongoing Research That Addresses Compatibility Issues

Research projects in various crop systems are attempting to answer these and related questions. Roberto Lopez, Assistant Professor and Extension Floriculture Specialist at Purdue University, and colleagues reported that fenpyroximate, even at 0.125 times the label rate for outdoor bell pepper production in Florida (equivalent to 13.3 fluid ounces/100 gallons of Akari 5SC), could reduce the numbers of adult A. swirskii by about 30% and the numbers of eggs produced by about 45% within 24 hours of application. The toxicity, however, reduced as the residue aged and the application rate was reduced.

Countless similar research projects are being conducted on various combinations of pest species, beneficial species, active ingredients, residue concentrations, and residue times. Pesticide manufacturers routinely test for the compatibility of their products as part of the product evaluation process. A BASF-sponsored study to assess the acute and residual impacts of Sultan on the survival and reproduction of A. swirskii and P. persimilis is on-going in the greenhouses at University of Florida (Lance Osborne), University of California (Jim Bethke), and Clemson University (J.C. Chong).

Proceed With Caution When Applying Pesticides

Pesticides are typically listed based on their toxicities or the mortality of beneficials when in direct contact with the pesticides or their residues. When a pesticide application is needed, always use the most compatible product. It is important to recognize that these databases are not complete. It is likely that a specific beneficial-pesticide combination may not be listed in the database. In that case, consult with your suppliers and always err on the side of caution.

There are quite a few approaches to this. Several operations are actually doing their own research on the compatibility of their most commonly used products to beneficials. This is to fill the knowledge gaps in the databases, as well as determining the best solutions for their unique situations.

When a pesticide must be used, select a product with shorter persistence or residue, so beneficials can be released safely soon after the pesticide application. Applying the pesticide using a selective or indirect application method, such as dipping or drenching, whenever possible also helps to reduce exposure. Spot treatment can reduce the proportion of growing area or beneficials impacted, but it is also important to make sure that a pesticide applied on one area of the greenhouse does not drift (yes, drift does happen in greenhouses) onto an area where beneficials are hard at work.

Lastly, in a comforting trend to the finishing operations that practice biological control, propagators are beginning to use beneficials. Working with your propagators to secure liners that are produced with biological controls or compatible pesticides may be the cornerstone to a more successful biological control program in your greenhouses.

Be Aware Of The Unintended Consequences Of Pesticide Use

Indirect effects of pesticides on beneficial organisms receive less attention from researchers and practitioners, but they are nonetheless as important as the direct effects. The application of pesticides can reduce pest population to such a low level that the beneficials cannot sustain a viable and effective population. Practitioners of biological control in greenhouses address this effect by making regular releases to maintain the beneficial density at a certain level, or by providing food supplements (such as alternative prey or pollen on a banker plant).

Julie Faucher Delisle of the University of Montreal and colleagues demonstrated that apple pollen supplements increased the control of western flower thrips by A. swirskii in greenhouse mum production. Vivek Kumar of the Department of Entomology and Nematology at the University of Florida and colleagues identified ornamental pepper (particularly ‘Red Missile’) to be an excellent banker plant and pollen source for A. swirskii. Indeed, banker plant systems are now available from several suppliers.

To develop a biological control program that accounts for the direct and indirect effects of pesticide application on beneficials is an extensive intellectual exercise. Seeking the knowledge and experience of other growers, suppliers, and researchers will help a novice or a seasoned practitioner achieve success with their biological control programs.

Page 2 – Online Sources For Pesticide Compatibility Information

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2 comments on “Biological Pest Control Starts With Accounting For Pesticide Compatibility

  1. Great points brought up here, especially concerning the full scope of the effect of certain pesticides. When using pesticides, it’s important to consider all of the possible effects it may have on the organisms (pest and non-pest) or even other pesticide treatments around it. Thanks for sharing.

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