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Boosting your BCAs

March 14, 2011  By Julie Graesch

Effective and environmentally sound pest management programs do not happen by chance

Effective and environmentally sound pest management programs do not happen by chance. Growers are routinely reviewing, revising and implementing new programs, practices and technologies to address emerging pests and challenges inherent in the greenhouse environment.

 WFT adult surrounded by S. feltiae.



Guided by the principles of integrated pest management, conventional synthetic pesticides are no longer considered the sole pest control option. In addition to better pest identification, regular scouting and implementation of more rigorous cultural practices, many growers have begun to adopt biological control agents (BCAs) to supplement, and in some instances, even replace, conventional pesticides. Greenhouse growers find BCAs an attractive addition to existing pest management programs because they offer short – or even no – restricted entry intervals, have limited impact to worker and customer safety, promote environmental stewardship, and are valuable pesticide resistance and residue management tools.

Insect parasitic nematodes are commonly used BCAs that can be incorporated into many pest management programs. Nematodes can be used as a stand-alone program or in conjunction with other BCAs, such as predatory mites and beetles, parasitic wasps and beneficial fungi. The combination broadens the pest control spectrum, and helps effectively manage all life stages in a pest population. Nematodes can also be used in a rotational program with conventional insecticides to reduce the number of chemical applications needed for effective pest control, reducing the likelihood that pests will develop pesticide resistance.

Untreated plant on the left with fungus gnat damage, and an S. feltiae-treated plant on the right


The insect parasitic nematode Steinernema feltiae is commonly used as a control option for western flower thrips (WFT) and fungus gnats. As with all pesticides, conventional or biological, applications of insect parasitic nematodes should coincide and target susceptible life stages of the pest.

For pests like WFT, it’s best to apply S. feltiae as foliar and drench applications. Begin applications with a drench early in the growth cycle and follow with weekly foliar applications. Drench applications target soil-dwelling pupae, whereas foliar applications target foliar-dwelling adult and pupal stages. By applying both drench and foliar applications, more stages of the thrips’ life cycle will be targeted, providing more complete pest control. Other BCAs that can be used with nematodes for control of WFTs include Orius spp., Amblyseius swirskii, A. cucumeris, Hypoaspis aculeifer, H. miles and Beauveria bassiana.

Many growers often utilize S. feltiae in a rotational program with conventional pesticides.

Under ideal environmental conditions for pest growth and development, populations may exceed the ability of BCAs to quickly decrease the pest population. In this instance, the quick knockdown often associated with conventional insecticides is desirable. Adding the insect parasitic nematode to a WFT spray program can significantly reduce the number of chemical applications needed for commercially acceptable levels of control.

Electric air pump and bubbler used to prevent settling of nematode solutions. Go to to find out how to make a nematode bubbler.


When used in a program with conventional pesticides, it is important to verify the compatibility of all BCA with insecticide active ingredients. Applications of S. feltiae should begin early in the plant growth cycle and chemical applications should only be used when action thresholds determined by the grower are exceeded. The application of BCAs can resume once the population is returned to a manageable level. Additional conventional pesticide applications are warranted if action thresholds are exceeded as determined by regular scouting.

Fungus gnats can also be targeted using BCAs. Begin using drench applications of S.feltiae, applying every two to six weeks to the soil/media. Applications of H. aculeifer, H. miles and Atheta coriaria will also reduce fungus gnat populations.

In addition to using S. feltiae, some growers use Steinernema carpocapsae for shore fly control. S. carpocapsae and S. feltiae can be tank-mixed and sprayed at the same time to target a wider range of pest organisms. Like WFT, the key to successful control of shore fly larvae is frequent applications.

For all BCAs listed, always apply early in the growth cycle when pest populations are low and follow all manufacturers’ product label directions to maximize control of target pests.

 Sticky cards are used for scouting.


It is important to remember that insect parasitic nematodes are live organisms that require specialized care during storage and the application process. It’s essential to keep nematode solutions from getting above 30ºC (86ºF), as well as ensuring the spray solution is constantly agitated to prevent settling in tanks. Failure to properly mix nematode solutions during application can limit efficacy. When nematode solutions settle out, a reduction in application uniformity will occur, resulting in an uneven distribution of nematodes and ultimately, uneven pest control. 

 Nematode specialist Julie Graesch. PHOTOS COURTESY BECKER UNDERWOOD


Growers use a variety of methods to prevent nematode settling, including: hand-mixing, mechanical circulation and air circulation. Air circulation (electric air pump, compressed air) is the most effective method for keeping nematodes in suspension and viable during application. Mechanical circulation (recirculating pump, paddle mixer, etc.) can also be used to maintain uniform distribution of nematodes in solution. When using mechanical circulation, care should be taken to prevent temperature increases and mechanical stress caused by the pump impellor. To minimize these effects, use solutions within two hours of mixing and add a cold pack to the stock tank.

Growers have adopted BCAs because of the growing concern with insect resistance associated with conventional pesticide programs, pesticide residue, inconvenience of personal protective equipment and re-entry intervals that reduce worker productivity. BCAs are an excellent solution to these concerns because, when integrated properly, they are safe to use on plants, can be used confidently around employees and customers to break the life cycle of pests, and finally, can prevent resistance issues while providing a similar level of control to conventional pesticides.

To learn more about insect parasitic nematodes and their compatibility within a comprehensive pest control program, visit or call 515-232-5907.

Julie Graesch is a nematode field development specialist at Becker Underwood where she is responsible for product development, as well as coordinating research opportunities with universities and third parties. She can be reached at

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