Understanding What’s Bugging You:
Preventing and Controlling Pests

By David K. Mueller


The best way to control a pest is by preventing it from entering your facilities or stored products in the first place. The goal of any pest management program should be zero defects and no customer complaints. This is not easy when the number of insecticidal products allowed is very limited; however, wholesome food without pests and unwanted pesticide residues is possible if you are willing to change the way you think about this challenge.

Step 1: Prevention. The most time and resources in a complete pest management program should be dedicated to preventing problems from occurring. This includes things like cleaning up spills, caulking cracks, replacing screens in doors and windows, placing a 30-inch gravel pest prevention barrier on the outside perimeter, correcting improperly installed outdoor lights, replacing door sweeps, inspecting pallets for carpenter ants and mouse droppings and sweeping and vacuuming spider webs in the warehouse. There should also be an 18-inch white strip painted around the perimeter of the warehouse between the wall and the product storage area where you can set up traps. Prevention takes time and diligence, but it pays huge dividends in a balanced food safety program.

Step 2: Monitoring. Think of this as a virtual thermometer for pest activity. If the pest population starts to rise, the monitoring tools will give an early warning before there is a pest outbreak that could seriously affect the reputation of a company and its products. Each building should be divided into individual rooms and identified with a number. All numbered locations should be put on a checklist for weekly inspections and checklists should be made in a way that you can go back year after year and see the history of the various sites. From this you can often make a prediction and take action before a problem develops. To monitor for pests you can incorporate pheromone traps (indoor and outdoor), mechanical mouse traps, sticky board traps, black lighting (to look for rodent urine and rodent droppings), a bright flashlight and nontoxic rodent census baits. The presence of spiders is also an excellent indicator of insect activity. Spiders eat insects and therefore indicate insect activity in that area.

Besides monitoring for signs of pests you should constantly be looking for things that might attract pests such as outdated product, which can harbor insects. The rancid odor attracts moths and beetles to the old product where the female can lay her eggs. Here they have a higher probability to survive and thrive. Rotation is key; even one bag of outdated grain based ingredient could become a nova for a large insect outbreak. Always ask: “How long has this been here?”

Step 3: Control. Too often the largest amount of effort and resources are expended on this portion of the program and pesticides become a crutch to replace valuable cleaning and monitoring. Control treatments should be a supplement to the prevention and monitoring programs. This part of the program should not be systematic or according to the calendar (e.g., every three weeks) but only as when needed. Outbreaks will occur in any pest management program and organic-compliant pesticides may be needed when these outbreaks occur. The frequency, however, of these outbreaks will be greatly reduced when a true menu of control tools is carefully used in combination to create a desired result. The selection of products to be used is based on the target pest and the history of the problem.

A post harvest organic pest management program differs slightly from a traditional pest management program. It starts with the insect or pest. Then you research what the target pest likes and doesn’t like. Now offer the pest what it doesn’t like and it will leave or it will die. This could be heat, cold, inert atmosphere, diatomaceous earth, insect growth regulators, fruit fly traps, pheromone traps, light or dark, screens or just simply shutting the windows and doors.

Knowing the pest is half the battle in controlling it. If you can identify the pest and research its behavior and habits, you are on your way to creating a program to eliminate it from your food products. For example, many insects are searching for a tropical environment. When products with high moisture are stored in a warm location, an outbreak often occurs. Some insects, like cockroaches, are attracted to dark, moist areas near drains and restrooms, while many flying insects are attracted to lights. Altering the environments that the pests prefer will cause them to relocate. A couple key case studies illustrate these steps.

Case Study #1: The Indianmeal Moth
This seed-feeding pest is found more often than any other insect in stored food. The adults are a nuisance pest that fly around your facilities and bother people. The larva stage causes the damage to food by feeding on the product, destroying the germination of the seed, spinning cocoons in the flap of a bag or spinning webbing over the surface of the product. This webbing contains fecal pellets and cast skins of the various stages of this larva that can adulterate food. Products that have nuts and dried fruits are very attractive to the Indianmeal moth. Newly emerged adults are bicolored and measure about a half inch from top to bottom. Their wings are light on the upper third of the wing and dark on the remaining part. This dark area can take on a purplish color.

The female Indianmeal moth lays 350 to 500 eggs during its short lifetime. This moth’s lifecycle is dependent on temperature and environmental conditions. In the summer, it will take five to seven weeks to develop. Eggs hatch after four to eight days and the larva will go from a microscopic size to a half inch in two to three weeks. It’s these small larva that can penetrate many food packages and cause customer complaints from the webbing that the larva spin while moving around in the packaged food material. There are four steps to take to prevent problems with the Indianmeal moth:

1. Good packaging is the best way to prevent infestations from occurring. Most infestations with this moth occur when the tiny 1 mm larva finds a defect in the bag and crawls inside. Products with no heat sealed inner poly bag are highly subject to infestation. Products with holes punctured in the bag to allow air out when filling are also vulnerable to these tiny larva.

2. Pheromone traps are sensitive monitoring devices that offer an early indication of moth activity before an outbreak situation occurs. They work best in finished warehouses, food processing plants and in retail stores. They are a vital part of a preventative monitoring program.

3. Temperature controls can prevent the development of insects. The Indianmeal moth does not reproduce below 65°F or above 105°F. Storing food in cool conditions will minimize the development of the insect. Freez-ing any suspect food products at 0°F for six days will eliminate any insect life. Also, heating a product to 140 to 160°F for 2 to 4 hours will also eliminate all forms of insect life.

4. Sanitation is essential to prevent insect growth and development. A female Indianmeal moth can lay her eggs on food that has been spilled under a cabinet. These eggs can become larvae that feed on the spilled food and survive to become reproductive adults that go out and lay 250 to 500 eggs, three to five times each summer.

Controlling Indianmeal moths, or any pest, takes an understanding of the life cycle and biology. If you find that they are attracted to something, remove it. Offer them the things they don’t like and they will leave or they will die. The steps above can help prevent and eliminate pest insects in an organic processing environment.

Case Study #2: Flour Beetles
These are difficult to manage because they are nocturnal and to hide in cracks and floors, they live a long time (9 months to 2 years) and their eggs survive the physical beating from milling and manufacturing.

The best way to manage them is to monitor with a flashlight for trails in the dust and use beetle pheromone traps to live capture the adults. Leave the live adults in the trap and they will produce natural pheromones to attract more beetles to the traps. Place one trap every 10 to 15 feet in areas where beetles are suspected, mainly near walls and support beams.

In addition to this, you can use heat treatment (140 to 160°F for 18 to 24 hours) and diatomaceous earth in cracks and voids. Mark the spots where you find dead insects after the heat up and concentrate on these areas with improved hygiene and approved insecticide products. You can also use an organic-compliant fogging insecticide with insect growth regulators (IGRs); non-toxic mimics of natural insect hormones that stop them from reproducing. Wait 4 hours between foggings and make sure to heat the area to 85 to 95°F to accelerate the respiration of the insects so they breathe harder. This combination will kill about 70 percent of the exposed beetles in 8 hours. Afterward, monitor with pheromone traps to determine the population rebound to see how effective the treatment was. Finally, use good sanitation to reduce their recurrence. It is important to remember that pest management works when there is not an outbreak of insects. Fumigation should only be used when you need to use a “big hammer” to gain control when there is an outbreak.

Take Home Message
A post harvest pest management program cannot work if the owner is continuously putting out fires or implementing Band-Aid solutions. Pest management starts with considerable time and resources invested in a preventative effort and is complemented by a thorough monitoring program. Finally, the safest control measures should be used, not according to the calendar, but when they are necessary.

David K. Mueller is a Board Certified Entomologist and the author of the book Stored Product Protection… A Period of Transition and the newsletter Fumigants & Pheromones. He the president of Insects Limited, Inc. and can be reached at Insectsltd@aol.com.

Note from the editor: The author’s list of suggested organic pest management tools is available by request.