[In the Field] Location

Pheromone traps are effective tools for monitoring stored products pests, especially stored food moths. Pheromone traps are most often used in large food warehouses and food processing facilities. Effective use of pheromone-baited traps requires more than simply placing the traps. No particular number of traps is right for any particular warehouse to detect the presence or absence of insects.

CHILL OUT. It is important to be flexible when starting a pheromone trapping program for the first time. The inspector must be prepared to move traps, add traps and adjust the trapping program in a building that is being monitored. Once a location is established as a quality site, then regular observations can provide consistent and comparable data for months or years to come. If you change the trap location, you should be careful not to rely heavily on historical trap catch data as the new location is capturing insects under different conditions.

Placement of floor-level traps is more challenging than with hanging traps. There is a natural funneling effect on crawling insects as walls and barriers meet at the corners. These are prime locations for pitfall and glue-board traps. Other prime locations for sticky floor-level traps are at door entrances. These traps often do not need to be baited and act as "blunder traps."

Equipment that processes food often has spills or accumulations and is highly susceptible to new infestations. Placing floor traps in those locations is important. The challenge to placing traps in these prime locations is that they are exposed to disturbances from cleaning equipment, human traffic, food debris, and even the natural elements. Placement of these traps in protective covers is an alternative, but these need to be tested carefully before committing to their use. Often, protective covers raise the glue trap or pitfall trap only a few millimeters off the floor, but this can stop a trap from catching insects. Trial and error is necessary to finally come up with the right combination of trap type, lures, location and protective devices that work best in any particular account. Some warehouses do not have steel vertical support beams, and in these cases the pallet racking or other means can be used to create a natural grid for a trapping program. Many warehouses have fire extinguishers set evenly around the warehouse, thus offering sites for traps.

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From the Field

Most lures will still have some pheromone remaining in them after eight weeks. The old lure can be left in the trap and a new lure can be placed next to the old lure. Old discarded lures should be placed in a sealed plastic bag and discarded in an outdoor trash receptacle. If you keep old lures for further use, store them in foil-lined pouches and keep them refrigerated. It is very important to use equally aged lures for each site that is being monitored. If a new lure has to be used due to a lost trap, keep in mind that it will likely be more attractive than older traps. This can create misleading information, false hot spots, poaching from other traps, and inaccurate population spikes. Replacement of all lures at once gives more comparable and accurate trap counts.

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Monitoring Tips for Pheromone Traps

Place traps on a grid

Place traps at eye level

Check traps weekly

Remove all old insects weekly

Write the date of the new lure on the trap

Keep thorough records

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The size of the grid will vary with the type of trap and facility, but as a general rule intervals of about every 50 feet will produce good results. If a facility is fully stocked with food products or seems to have an infestation, the interval distance should be reduced to 25-30 feet to improve coverage and enhance the probability of detecting small outbreaks. Traps should also be placed near potential insect harborages such as corners, beams, and entry and exit points (i.e. interior corridors).

In typical situations, traps for flying insects should be placed at a height of about 6 feet for servicing convenience. Moths, however, can fly at ceiling heights where it is often warmer. Traps need only be placed at these heights if easily accessible with stairs. Avoid placing traps near exterior doors and windows to avoid possibly luring insects inside from outdoors.

Many times, a trap may become inaccessible or lost behind pallets of product. During some weeks, these "buried" traps may have to be skipped when record keeping is performed. If the trap must frequently be skipped, however, it should be moved to a different, more easily accessed location.

The use of pheromone traps should not be limited to large food warehouses and food processing plants. They can be useful too in smaller facilities (i.e., restaurants, grocery stores, pet stores and even private homes). A few well-placed traps can be an early warning system to detect newly arrived infested goods and help prevent wider insect infestations.

The authors are technical director, technical manager and president, respectively, of Insects Limited, Indianapolis, Ind.