What is Bugging You?

What bugs are bugging your facility?

In the food industry, the list typically includes the common stored product insects, such as Indianmeal moths, red and confused flour beetles, saw-toothed grain beetles, cigarette beetles, a few fungus feeding insects, and the notorious warehouse beetle. Since these have been around for so long, the industry seems to have accepted them as a part of doing business. That is, until our customers remind us that they do not consider the presence of bugs in food products to be a value-added benefit!

In the last two years, the warehouse beetle (Trogoderma variabile) has become the most noticeable and most difficult stored product insect to deal with. There are many factors contributing to its increase in activity in food plants, but perhaps most notable is the lack of understanding of how to deal with it…a trend that appears to be growing in many segments of the industry.

This remarkable insect is often under appreciated. Recent experience has shown the warehouse beetle to be just as comfortable living outside your facility as inside. Due to its small size, passage from the outside to the inside is fairly simple. Whether you are in Minnesota or Texas, if you are experiencing warehouse beetle issues, it is important for you to know what is going on outside your facility. A few pheromone traps placed 100 feet away from your facility just may give you shocking news.

It is not unusual for this insect to follow the seasonal migrations of cluster flies, boxelder bugs, and Asian beetles into your facility during their trek to their winter habitat. These and other insects are a major food resource for warehouse beetles as they find their way into the wall and ceiling voids for the winter. This habitat suits the warehouse beetle quite well since it prefers the darkness provided by these out-of-the-way places and abundant food supplies.

Migrating insects are often handled through the use of insecticides that fog the processing, warehouse, and ceiling voids to knock them down. Unfortunately, this tends to play right into the warehouse beetle’s comfort zone, because we seldom go back and clean up the dead carcasses left behind, creating an all-you-can-eat buffet for the warehouse beetle—that will eat the interior of the exoskeleton of the insects they are feeding on.

Everyone likes a little diversity in their diet, and the warehouse beetle likes it all. It will live off dead animal material, dead insects, cereals, milk powder, spices, fish meal, potato chips, pollen, and a variety of other processed foods. What does your food plant offer on the menu?

Controlling the Beetle. There are a number of biological and behavioral traits that we can use to our advantage when dealing with the warehouse beetle. The fact that its adult life is relatively short-lived makes it an excellent candidate for a pheromone trap. One mistake often made with this insect is that, because it flies, people tend to only use aerial traps. These traps are excellent, but the warehouse beetle actually spends the majority of its time crawling, particularly when temperatures drop below 72°F. Placing floor traps in sensitive areas is just as important in the monitoring or investigating part of the control program. I would caution that the application of pyrethrins can affect the efficacy of the pheromone traps for up to a week after ULV application.

When pheromone traps are used, the placement suggestions provided by the manufacturer are a good place to start. The facility should be set up in a grid pattern, mapped for trap locations, and checked daily initially to determine the level of activity. Weekly checks should be conducted after the traps have shown no activity or a distinguishable pattern. If the numbers begin to increase, so too should the frequency of monitoring. In areas where activity is noted, shrink the grid to help zero in on the likely material or location harboring the infestation. Trending the data over time is particularly important in gaining an understanding of “hot spots.”

As previously mentioned, the warehouse beetle prefers a dark habitat. This should lead you to begin to look at wall voids, ceiling voids, components of equipment (such as hollow tubing with openings), conduit/electrical systems, and, in some cases, the flutes on cardboard boxes contaminated with food residue or powder. These are areas of great concern.

When a facility has been constructed using corrugated metal sheeting, it is almost a given that there will be a problem if this material was used for interior partition walls in dusty areas or those cleaned with compressed air. Wherever there is a void space in a wall, product is likely to collect inside and support this insect. There are only two options to remedy the situation: removal of one side of the wall to provide access for cleaning or replacement of the entire wall with a metal-clad foam panel to eliminate the void space. Then make sure all joints are properly sealed.

Dealing with a warehouse beetle infestation can often be a very time consuming, labor intensive process, and sometimes involve expensive structural modifications. The more you know about this insect, the more successful you likely will be at reducing its presence or eliminating it from the facility.

This brings us back to where we started. How do you deal with these bugs? In just about every instance, I am told that arrangements have been made with a pest control company to fog the facility. The typical schedule is every two weeks to once a month. The overall results are unknown, but it seems to be helping. However, what is the post-treatment inspection for dead insects telling you? What counts are you getting in the pheromone traps and insect light traps? In many cases, the chemical application has done little to improve control, and often it simply aggravates the situation.

Insect growth regulators (IGR) are an often overlooked part of the warehouse beetle control strategy. Since this insect can spend a considerable amount of time in the larval stage, IGRs can have a significant impact on the population because they remain in place long after the pyrethrum formulation is gone. Exposure in the larval stage can reduce the chances of the insect becoming a reproductive adult.

The major challenge with relying on a space or ULV application to control this insect is that these beetles spend most of their time in darkened areas where the material will not likely reach. Removing a few ceiling tiles and pointing equipment up into the ceiling to kill warehouse beetles that might be up there is rarely effective because the correct volume is often not used, and it ends up forcing the population deeper into the structure.

So what can be done? This can vary from one facility to another, but there are some basic guidelines to follow:

1. Educate yourself about the insects you will likely encounter. Their biology and behavior will give you great clues as to how to proceed effectively and efficiently.
    
2. Implement the appropriate monitoring program using pheromone traps to assess the population and the areas where activity is present. Include both flight and floor styles in your program.
    
3. Inspect, inspect, and inspect some more!
    
4. Identify all materials that are showing signs of insect activity, and deal with any that are damaged before they get infested. Remember, the warehouse beetle is excellent at chewing through packaging to get inside the bag. Look for the small holes or live insects on the outside of the product.
    
5. Locate and remove any spillage. Particularly around rack or equipment support legs. In the racks, look up to identify if any product remains from split bags someone already removed, but left the spillage behind. Many of the racks currently in use have openings in the hollow formed-steel supports where product can and does collect.
6. Take a close look at the structure for holes in the walls where equipment has been removed, pipe penetrations, or any opening into a void space.
    
7. Find dust and look for trails. Upper ledges, the top of structures, and equipment storage areas where equipment parts were placed without cleaning are all excellent sites for this and other insects. Sometimes the older the dust, the more revealing it can be.
    
8. Look up and check fluorescent light fixtures. If they have shields on them, the insects can find their way in and die.
    
9. If necessary to get the answers you need, open up walls to check for product accumulation and insect activity. Unfortunately, the only solution to this issue will likely be to replace what you have with alternative materials without the open voids. Attempting to do this post-construction by injecting foam into the void space between corrugated steel will likely be unsuccessful because voids may still be created as the foam cures.
    
10. Check ventilation and dust-collection systems for activity. Both of these can be an important source of warehouse beetle activity. If dead insects remain on the filters or in the housing of the HVAC unit, warehouse beetles from the outside may find them, feed, and get drawn into the plant. The same can be true with dust collection units, because it is common to have product buildup inside the lines become infested. Many such systems do not have adequate access for cleaning to be accomplished.
     
11. Perhaps most important is to check your service contract and demand a level of service appropriate for your facility. To effectively deal with an infestation of warehouse beetles, the scope of service needs to include all of the above, which is far beyond the simple monitoring of rodent control devices. An in-depth IPM assessment is the first step in this process. This has to be conducted by knowledgeable individuals who have taken the time to learn about your issues and are willing to commit the time to do the program correctly.
     
12. The work to control the population will be a joint venture. This will require extensive communication between the plant and contractor. This communication is more than just a service slip generated by a scanning unit with pre-written statements. It will require clear and concise directions on how corrections will need to be handled. The program must be a partnership with each side understanding what must be done.

These steps can easily be applied to many of the insect issues that food plants and warehouses face. Replace the warehouse beetle with the Indianmeal moth and the formula for success is essentially the same. Understand your target, and use this information against it. This brings you beyond the realm of having good luck and into the realm of using good science to be successful.

The author is Head of Food Safety Education, AIB International.