How biological controls are applied can affect their success as part of a pest control program-and proper handling of nematodes is no exception.

How biological controls are applied can affect their success aspart of a pest control program-and proper handling of nematodesis no exception.

Chart 1

Comparison of circulation method on nematode solution temperatures over eight hours.

  • Temperatures of stock solutions mixed by using air circulation remained relatively constant over eight hours.
  • Temperatures of stock solutions mixed by using mechanical circulation caused temperatures to rise above 95<0x00B0>F (35<0x00B0>C) over eight hours.Temperature increase in stock solutions can be mitigated by the addition of cold packs.

Chart 2

Comparison of circulation method on application uniformity over time.

  • No circulation resulted in rapid settling of nematode solutions over time. If stock solutions are not mixed, application uniformity will be poor and pest control will be inconsistent.
  • Air and mechanical circulation both maintained uniform mixing of nematode stock solutions. Adequate mixing is essential for efficacy.

Chart 3

Comparison of circulation method on nematode viability and infectivity over time.

  • Rapid settling reduced mealworm mortality in not-circulated control.
  • Mealworm mortality was relatively constant over time when air circulation was used to mix nematode stock solutions.
  • Increases in temperature and mechanical stress over time reduced viability of nematodes mixed by using mechanical circulation.
  • Nematode solutions should be used within two hours to maximize efficacy when using mechanical circulation.


Entomopathogenic nematodes can provide biological control of insect pests of ornamental plants, whether used exclusively or as part of a coordinated program.

Insect-parasitic nematodes offer the flexibility to be used as tools incorporated into many pest management programs. Nematodes can be used as a stand-alone program or in rotation with conventional insecticides to limit development of pesticide resistance. Because insect-parasitic nematodes have no adverse effects on beneficial insects or microorganisms, they can be used in conjunction with other biological control agents to broaden the pest control spectrum.

Proper handling of insect parasitic nematodes during application is vital to assure effectiveness. It’s important to keep nematode solutions cool and well mixed to prevent settling in tanks. Proper mixing of nematode stock solutions often is overlooked in the application process. Failure to mix nematode solutions will severely reduce application uniformity. If nematodes are allowed to settle, excessive numbers of nematodes will be applied to some areas, while other areas will receive no nematodes, resulting in uneven pest control. Various mixing methods, like hand-mixing, mechanical circulation and air circulation, are used by growers.

Based on research conducted at Becker Underwood, we recommend air circulation as the best method for keeping nematodes in suspension during application. Mechanical circulation (using a recirculating pump, paddle mixer, etc.) also can 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. Use the nematode solution within two hours of mixing and adding a cold pack to the stock tank to maximize nematode viability when using mechanical circulation.

A case study: nematode circulation over time

In this case study performed by Becker Underwood staff, three circulation treatments were compared to demonstrate the importance of keeping nematode solutions cool and well agitated. Three nematode stock solutions of 250 million nematodes per quart were created and were not mixed (control), or mixed by using air or mechanical circulation for a period of eight hours. The air circulation equipment used for the experiment was a Dramm (Manitowoc, Wis.) electrical air pump attached to a bubbler, and the mechanical circulation equipment was a battery-powered bilge pump (Marine Metal Products, Clearwater, Fla.). A Dosatron® (Clearwater, Fla.) unit at a 1:100 injection ratio was used to sample each stock solution zero, two, four and eight hours after mixing. The Dosatron intake was positioned at the top of the solution column in an effort to maximize differences brought on by nematode settling. At each sampling time, the number of nematodes applied, solution temperature and nematode viability were determined. The charts (Page 12) provide a graphic representation of case study results.

The incorporation of nematodes into a comprehensive pest control program can increase its effectiveness, provided appropriate application methods are practiced. Of course it’s important to consult labels and follow prescribed procedures, and with a bit of care, your control program can provide the results you need.

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

Take Home Messages

  • Adequate mixing is essential for uniform nematode application and to maximize pest control.
  • Air circulation generally is the best method for keeping nematodes viable and solutions properly agitated.
  • Nematode solutions should be used immediately. Apply solutions within two hours for mechanical circulation and within four hours for air circulation.
  • Adding cold packs to nematode stock solutions will ensure cool temperatures and maintain nematode viability during applications.