Insect Monitoring in Food Plants

Facilities that process food come in many different forms — from those that process whole grains into raw ingredients to those that manufacture grain-based products, bakeries, beverage production, pet food processors and meat-packing facilities. Each is unique in its design and purpose, building maintenance, location, and pest threats and issues. The pest management plan should be specific to each facility, although many pest management strategies remain constant for all food processing, packaging and storage.

Fresh out of college from Purdue University, I spent much of my early pest control experience in Indianapolis in grain elevators, food warehouses and food-processing facilities. Later in Houston, Texas, I performed pest control QA inspections for large food plants that manufactured rice products, beer and other foods. I learned on the job, and this article reviews some of the tips I learned then, and since, in monitoring stored product pests in food-processing related facilities.

SITE SURVEY. The facility type and layout of the building determines much of the strategy for placement of insect monitoring devices. For example, a facility making baked goods (i.e., bread) likely requires monitoring in raw ingredients storage, in production (including some of the machines), and in the shipping warehouse. A facility that produces packaged meat products (i.e., canned meats) may primarily require monitoring for stored product pests in the area where grain-based ingredients and/or spices are located. A facility located in a rural area near farms may also require outdoor monitoring stations.

Interviewing the customer and asking to examine past pest activity records helps greatly in determining which types of insects to target and which areas require monitoring. Facilities with grain-based products will almost always want to target Indianmeal (IMM) and other moths and possibly flour beetles and warehouse beetles (Trogoderma spp.). Pet food manufacturers may also want to monitor for cigarette or drugstore beetles in addition to IMM and maybe larder beetles. Examine past pest activity to determine which insects to target and also include the customer’s preferences.

The customer also may provide a list of sites within the facility they want to have monitored. This list typically includes any areas mandated by the third-party auditing agency used by the facility. The auditing agency’s requirements may also provide which pests to target and which monitoring devices may or may not be used. All of these factors need to be inputted into the monitoring plan.

Last, a visual inspection may detect insect activity in sites where it previously has not been noted. Food plants are huge and complicated facilities and limited activity may go unnoticed until populations grow large, especially for some types of beetles (e.g., flour beetles, fungus-feeding beetles). I once inspected a bakery facility and found a few confused flour beetles; these were traced to the flour dust collecting on top of big pieces of machinery and overhead pipes. Such sites were not suitable for placing beetle traps but required routine checks by the pest professional and the facility’s QA manager. Areas that require routine visual inspections should also be part of the monitoring program.

FLOOR PLAN. Use a floor diagram to chart the location of pheromone devices, beetle traps, insect light traps and general insect monitoring traps/devices. The same floor plan can be used to diagram the locations where insect activity has been noted. Different-colored ink or symbols can be used to denote current vs. old activity. For digitally savvy professionals, the floor diagram can be inputted into whatever software is being used and the appropriate symbols used to show locations of both activity and placement of various monitoring devices.

PHEROMONE CONSIDERATIONS. Several factors come into play when using pheromone monitoring devices.

Moths — A number of different pheromone trap styles and lure types are available for the Plodia moth complex (stored product moths). Lures have varying pheromone concentrations which affects how far apart to space them and how long they will last.

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In general, locating moth pheromone traps at 50-foot intervals works well in warehouses; often support posts for the building will be at 50-foot centers and are good locations to mount traps. This trap spacing works in warehouses but may not always be ideal for the food processing or packaging areas of a food plant.

For large processing areas, locate traps close to sites most likely to have moth breeding, such as where any dried food ingredients are handled and processed in the area. Attach traps to support posts or hang on walls spacing up to 50 feet apart at most. If the facility has no real history of moth activity in processing, traps may not be necessary until activity occurs. This factor applies also to areas where foods are packaged before moving to the warehouse.

Pheromone lures may also be located inside ILTs, if any are present, to enhance the monitoring program.

Multi-Pheromone Trapping — In facilities that have two or more different insects to monitor, lures for each insect type may be used in each trap. For example, it is not uncommon to monitor for IMM, cigarette beetles and Trogoderma beetles in particular facilities.

Dusty Conditions — Food plants that use flour (i.e., bakeries) and ground-up grains often are dusty, sometimes extremely so. Heavy amounts of dusts can cover glues inside moth traps and other sticky monitoring traps, affecting the traps’ ability to catch insects. In such cases, take into account the added cost for regularly replacing traps and transferring lures to the new traps.

Beetle Traps — Traps designed for capturing crawling beetles (e.g., flour beetles, sawtoothed grain beetles) are available for monitoring these species. Such traps should be placed close to sites where such beetles are most likely to occur such as beside the bases of storage racks in warehouses where dried foods are stored. In processing areas, beetle traps may be placed inside machinery where these can be safely placed, usually machines that are enclosed. They may also be placed/secured on top of beams, pipes and other horizontal surfaces where they are (1) off floor level and (2) secure from falling into processing machinery. Beetle traps should not be placed in the open along floors in processing and packaging areas. Use the initial survey to decide trap placement, taking into account those sites that have higher risk for activity.

Crawling Insects — Plastic stations designed for holding glue traps or insect monitors may be located in a secured fashion along walls where these may be permitted to monitor crawling insects. Glueboards placed inside Tin Cat-style mouse traps serve dual purpose by also monitoring for crawling insects in warehouses. Moth and beetle pheromone lures may be placed inside such devices to attract and capture target insects, thus adding additional monitoring to standard pheromone traps used in the facility.

Exterior Trapping — Some food warehouses and food plants may be located in areas near cropland, grain elevators or similar locations where certain stored product pests may be prevalent outdoors.

Weather-resistant monitoring pheromone traps are available to use for monitoring the levels of target moths or beetles outside. Also, where outdoor target insects may be prevalent, avoid locating traps close to doorways in warehouses where doors may be opened for periods of time. Otherwise, you may attract insects inside.

The author is a consultant based in Eads, Tenn.