MONITORING FOR STORED PRODUCT PESTS

The proliferation of synthetic insecticides during the last half of the 20th century gave the pest management industry effective chemical remedies for many insect pests. These materials seemed to offer a panacea for all the problems these pests caused our customers. Synthetic insecticides were used by many but, unfortunately, they were sometimes used unwisely. It was perhaps inevitable that this misuse would be criticized and bring tighter regulations.

The process of tightening regulation continues, as exemplified by the phasing out of methyl bromide (because it has been identified as an ozone-depleting substance), and the process of mitigating the human exposure risks associated with phosphine fumigation. The eventual loss of methyl bromide is of particular concern to the milling and food-processing industries, which have relied heavily on this fumigant to control insect infestation in processing plants. Much effort has been spent in seeking alternatives to methyl bromide for a wide variety of applications and it is generally agreed that there will be no single replacement. Instead, the alternative for each application will be an integrated system of control measures that will be applied only as needed and in a manner that balances risk against efficacy and cost effectiveness.

This system of pest management should prove to be the most sustainable in a climate of increasing public concern about the potential risks posed by pesticides.

ESTABLISHING AN IPM PROGRAM. The pest management solution for the food-processing industry may eventually include an alternative fumigant, such as sulfuryl fluoride, which does not deplete ozone, but any fumigants or other pesticides used for stored product pest control should be part of an Integrated Pest Management program.

The best way to maintain the privilege of using these chemical tools is to use them wisely. This is vital if we are to ensure that they will be available to us in the future and this can be done best if they are used as part of an IPM program.

What are the components of an IPM program for warehouses, mills and food-processing plants? It will obviously include preventive measures, such as sanitation and sealing of cracks and crevices. It will include application of various control measures (fumigants, other conventional pesticides, biorational chemicals [such as insect growth regulators], physical methods [such as high temperature], etc.) when and where needed. And it will also include regular monitoring of pest populations. Monitoring is an essential part of any IPM program because it is the only way to know when and where to apply control measures and what type of control measures are needed.

There are several ways to monitor insect populations: visual inspection and counting insects on walls and other surfaces, trapping with pheromones or food attractant baits, or counting insects in samples of mill tailings. But how do these monitoring tools accurately and efficiently identify when and where control intervention is necessary and what type of control measure or measures should be applied? Knowledge of pest biology and ecology is critical to making the right treatment decisions that will result in commercial success. Yet, surprisingly little is known about stored product pests in commercial settings. How rapidly do populations of various species increase in warehouses, mills or food-processing plants? What population levels or numbers counted or trapped require action? What are the economic thresholds for treatment?

CONCLUSION. Different monitoring tools may lead to different conclusions. Which of the tools are best in a given situation? Should they all be used? If so, how can they be used most effectively? Using insect monitoring tools accurately and efficiently for making pest management decisions requires considerable thought and knowledge that is yet to be gained.

My associates and I are working to determine the best ways to use the monitoring tools we now have and to develop new tools where they are needed. Our work so far has focused on monitoring in retail stores and in warehouses. A combination of trapping and spatial analysis of trap counts was used to locate centers of infestation and target these centers for control intervention. The value of this type of monitoring is illustrated by the results of our research in retail stores. The maps on page 76 indicate trouble spots that require action, show the effectiveness of action taken and provide graphic representation of infestation for managers and pest control operators.

We will be extending our research to include mills and food-processing plants and will incorporate other methods of monitoring. The results will be published in a future edition of PCT magazine.

The author is a research entomologist at the Center for Medical, Agricultural and Veterinary Entomology, ARS-USDA, Gainesville, Fla. He can be reached via e-mail at tarbogast@pctonline.com.