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Mullen's Musings™

Help! I Put Out Pheromone Traps and I Caught Hundreds of Bugs!
What Do I Do?

By Dr. Mike Mullen

This is a question often asked by users. In our last issue, we learned about how many companies use pheromone baited traps in their facilities. To answer the question above, let's first review are a few important points.

What Pheromone Traps Will Not Do
Pheromone trapping is an essential tool in monitoring insect populations; however, it does have its limitations. In general, trapping alone is not a control measure, but is an essential part of an effective integrated pest management (IPM) program.
Pheromone trap monitoring is not a substitute for sanitation.
Pheromones will not attract immature pests and are specific to certain groups of insects.
Most pheromones are sex-specific and will not attract males and females.
Pheromones classified as aggregation pheromones will attract both males and females, but are not as effective as the sex pheromones.
Large numbers of insects may be captured in traps. But remember, most insects mate several times and are capable of producing large numbers of offspring. Therefore, the number of insects trapped would have to be about 95% of the total infestation, or above, to have a significant impact on pest populations over the relatively short period of time that finished products are stored.
Good results with mass trapping cannot be assumed with pheromone traps.
No pheromone will cause an insect to leave a suitable food source.
Pheromones will only capture pests in transit from one food supply to another.
Food odors (kairomones) in traps will attract pests, but poor sanitation will negate their effectiveness.

What Pheromone Traps Will Do
Pheromones will alert the user to low level populations before they become serious.
Pheromone use will lead to reduced dependence on chemicals by locating those areas that need spot treatments.
An effective monitoring program can be used to evaluate the effectiveness of control procedures.
Monitoring outside of a facility will give some measure of the movement of insects in and out of the facility.
Pheromone traps will decrease insect visibility
Trap interpretation

Now, I will help you interpret the information traps provide.

Generally, Indianmeal moths traps should be placed in a grid pattern about 12 to 15 meters apart.
Trap height has little impact on the effectiveness of moth traps, so a height of about 2 meters is adequate to keep them out of the main traffic flow and still be easy to check.
Beetle traps can vary greatly in their effective range. The Confused and Red Flour Beetle pheromones are only effective for a range of 10 to 15 meters, while Warehouse, Khapra and Cigarette Beetle pheromones are effective over a much wider area.

Also consider the behavior of the pest when interpreting trap information.

Moths, Warehouse Beetles and Cigarette Beetles are good fliers and, as a result, the effective range of the pheromone can be extended from the floor to the ceiling. However, Flour Beetles and Khapra Beetles do not fly, so traps are only effective when placed close to the ground. The Red Flour Beetle is capable of flight, but rarely flies.
As insects migrate through a facility, they tend to move toward the walls. Of course, they cannot move farther, so expect higher numbers to be trapped in these areas.

Now that I have digressed, lets get back to the original topic: "What do all these bugs mean?"

The simplest and most widely used method to interpret trap catch is to look for trends in numbers of insect captured from one sampling period to the next. In this way, the user can detect changes in numbers that could indicate a developing pest population.

The traps should be placed in a grid pattern around the facility using the manufacturer's recommendations for the effective area for each trap. Comparing numbers of trapped insects from one trapping period to the next can provide the user with a great deal of important information. However, it is difficult to pinpoint the location of the infestation without additional time and effort. Once an area is found to be the focus of the infestation, the traps must be concentrated to "pinpoint" the infested area. This method requires several weeks to accurately pinpoint infestations. Also, during the search for the infestation it is essential that the remainder of the facility be monitored for other infestations.

It is critical that careful records be kept, of course, as in all monitoring methods. These records should not only include the number of insects trapped at each location, but also the location, the date each trap was put out, checked and when the lure was changed.

Dr. Christian Nansen, using a hypothetical warehouse, proposed a modification of this method (see Pest Control, 72: 36-38, 2004). In this report, he cites several factors that might impact trap catch from week to week. These factors include:
• an open window
• lights on or off that could impact insect flight
• ventilation and implementation of a sanitation program during that time period

In Nansen's report, the trap(s) with the most insects captured is called the "centroid" and is given a weighted score (percentage of the total trap catches). Each week this centroid may change and would be an indication of the change in insect populations and their direction of movement. This method reduces the importance of numbers trapped, but gives an indication of population increases in defined areas of the facility. Using a map of the warehouse, the movement of the infestation can be charted. While effective, Nansen's method can be time consuming and often it is critical that accurate answers be obtained over a shorter period.

Spatial statistics are a powerful tool that can be used to accurately determine the location and movement of infestations over time. The spatial mapping method is often used to show how insect populations spread through a commercial pet food facility. This information will allow the warehouse sanitarian to pinpoint control procedures that greatly reduced infestations throughout the facility (see J.F. Campbell, M. A. Mullen and A.K. Dowdy, J. Economic Entomology, 95:1089-1101, 2002). The more traps used, the more accurate the predictions will be.

One of the primary advantages of this method is that traps are placed in only one location, and moving them is not required. The information gained through trap capture allows the contour maps to be produced that show relative insect populations and the extent of those populations. Once those maps are overlaid on a facility floor plan, it is easy to locate infested products. These maps are easy to interpret and provide the user with a simple means to visualize infestations. Many pest management professionals have adopted contour mapping as an accurate means to locate insect infestations, and with some training, plant sanitarians can use the program effectively.

There is little doubt that using pheromone-baited traps is the most cost effective method for the early detection of insect pests.

Traps work 24 hours a day, seven days a week.
Traps require minimal maintenance.
Traps can be used effectively by minimally trained persons.
Pheromone lures must be changed on a regular schedule.
To get the most from your trapping program, it is essential that accurate records be kept.
Traps should be checked at least weekly during warmer periods that are favorable for insect development and every two weeks during colder weather.
Trapped insects should be removed to avoid confusion during subsequent counts.
Trap use will lead to reductions in pesticide use.
Traps are an important element of IPM programs.
An adult insect's main function is to reproduce to perpetuate the species.
Despite claims that you may have heard, no pheromone or food bait will make insects leave a food source.
Pheromones are most effective in a clean environment, so sanitation is essential.
Remember to send your questions and comments regarding Mullen's Musings to our customer service staff at custserv@trece.com and one of us will get back to you with answers.


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