What are insect pheromones?
Pheromones are chemicals that are released by insects as their principal method of communication. Insects live in a world of odors. They use olfactory cues to direct social behavior, including mate attraction, courtship, mating, egg-laying, foraging for food, and colony defense. Pheromones are released by insects and other organisms into the environment in order to communicate with others of the same species. These pheromones are specific single or blended compounds (often alcohols and aldehydes).
Types of pheromones used in lures
While insect communication is directed by a number of different pheromones, there are two types of pheromones commonly used as lures for stored product insects and other urban pests: sex pheromones and aggregation pheromones.
- Sex pheromones are nearly always produced by females to attract males. Adults of species with short life spans of only a few weeks (e.g. clothes moths, cigarette beetles, and warehouse beetles) usually produce sex pheromones. One result of this short life span is that females produce sex pheromones that are highly active and attractive to males. Male insects can be so sensitive to these pheromones that only a few nanograms (1 billion nanograms = 1 gram) can cause a male to search for the female. These pheromones can be active over distances of several hundred feet and in some cases (e.g. gypsy moths) even miles away.
- Aggregation Pheromones attract insects to favorable locations where mating occurs and where females find egg-laying sites on food substrates. Aggregation pheromones are typically released by males to attract BOTH male and female individuals. They are produced in species with long adult life spans of several months to years (e.g. most stored food beetles). The attraction distance of these types of pheromones are also much shorter than with sex pheromones. Often the distance is measured in a few feet (< 20 feet). Certain compounds of some aggregation pheromones are not species specific, (e.g. Flour beetles) and there is cross-attraction, especially among closely related species (e.g. Red and Confused flour beetles). In most cases, foods synergize the effect of aggregation pheromones.
How pheromone lures work
Pheromones are extremely species specific in the way they work. It is essential to get an informed insect ID before using pheromones lures.
Pheromones are identified and synthesized in chemistry labs, and then placed into a delivery device, or lure. These devices come in various forms: rubber septa, hollow fibers, flakes, tape, laminated plastics, membranes over reservoirs, and polyethylene vials with acetate beads. The lure design should deliver the pheromone into the environment in a manner that mimics natural release rates and concentrations of the target insects. Lures vary in duration of effectiveness and distance of attraction due to differences in pheromone load and release rates. Many insects can be overpowered and repelled by too much pheromone. A controlled-release lure will allow the pheromone to be released in a concentration small enough to entice the pest into the trap, but strong enough to reach out and pull them in over a useful distance.
How to use pheromone lures as part of a monitoring program
- First identify the insect that you would like to monitor.
- Make sure that the pest you want to monitor has a viable, commercially available sex pheromone lure.
- During the monitoring period, keep the doors shut in the storage area that is being monitored as much as possible. This will minimize the chances for pests from adjacent storage areas or outdoors from entering.
- Keep the pheromone lures at least 15 feet (5 meters) away from any door that is being opened on a regular basis.
- Set up the traps in a grid pattern. Once you start receiving numbers in the traps, adjust their locations to help you pinpoint the source.
- After pinpointing an area of infestation with traps, use visual assessments to locate the specific source.
More information is available at Insects Limited.
Benefits of using pheromone lures
Trapping is an essential part of any IPM plan to monitor, identify, and locate insect populations so that control measures can be efficiently implemented. Insects that have found ideal harborage sites and food sources within collection areas may not be caught by “blunder” traps since they have little incentive to travel. Pheromone lures, if used correctly, can significantly increase the efficacy of monitoring.
The University of Florida published a study of insect attractants and traps that found attractant-baited traps are used instead of (or in addition to) other sampling methods for two major reasons:
- These traps are very sensitive and may capture pest insects that are present at densities too low to detect with a reasonable amount of effort using other inspection methods. This attribute can be extremely important when the goal of a sampling program is to detect foreign or “exotic” pests as soon as they enter an area so that control measures can be initiated immediately.
- Traps baited with chemical attractants capture only one species or a narrow range of species. This specificity simplifies the identification and counting of target pests. Sensitivity and specificity make attractant-baited traps efficient, labor-saving tools. (Weinzierl, R., T. Henn, P. G. Koehler and C. L. Tucker. 2005. Insect Attractants and Traps. Alternatives in Insect Management. Office of Agricultural Entomology, University of Illinois at Urbana-Champaign.)
A valuable attribute of pheromone baited traps is the fact that they can aid in pinpointing an infestation within a large storage area. Traps should be closely monitored to assess captures, and reorganized so that traps are placed within areas that show the highest capture rates.
Potential risks of using pheromone lures
Pheromone traps, when used correctly, will not draw unwanted pests into an area being monitored. The sex pheromone of common museum pests like, cigarette beetles, clothes moths and carpet beetles will only attract the adult male insect. Sex pheromones that mimic the female insect will never attract a reproductive pair, the damaging larval stage, or a female insect with eggs. The strength of the pheromone is generally not strong enough to pull from outside of the space that you are monitoring. Using the following guidelines to help you use pheromones to monitor and locate sources of damaging insect pests will prevent any unwanted insect entry into a museum or storage. Pheromone traps are species specific so they will not pull in other types of pests.
These precautions are recommended to prevent pheromone traps from pulling insects from surrounding areas into collections:
- Pheromone lures should be kept at least 15 feet (5 meters) from any door that opens to the outside.
- Pheromones are not recommended for areas such as loading docks or cafeterias that might be adjacent to collection storage areas.
- Pheromones should be removed from packaging using tweezers or gloves (rubber or nitrile) and immediately placed in the trap. Pheromones should never be placed in contact with collection objects, storage containers, or display mounts. Physical contact with a pheromone lure will transfer pheromone molecules (micrograms) to an object or person.
The question as to whether pheromone molecules in air adsorb onto materials and turn the materials into “lures” themselves is unlikely, but would benefit from additional research. Materials such feathers, skins, furs, hairs, and textiles have potentially greater adsorption capacity than other objects. The natural food odor of the material, however, is what primarily attracts the clothes moths and dermestids to these items. It has not been proven that the minute amount of pheromone in the air (from normal monitoring use) can cause an object to become statistically more attractive than one not in the presence of pheromone.
All pheromones lures have been found to be safe for humans. With pheromones, as with all chemicals, it is important to refer to the MSDS (materials safety data sheet) and other manufacture safety guidelines to ensure that the material is safely stored and used.
Commercially available pheromone traps
Insect pheromone traps are species specific. Traps with sex pheromones for one species will not attract other species.
- Almond Moth, Ephestia cautella
- Angoumois Grain Moth, Sitotroga cerealella
- Brown House Moth, Hofmannophila pseudospetella
- Casemaking Clothes Moth, Tinea pellionella
- Indian Meal Moth, Plodia interpunctella
- Mediterranean Flour Moth, Ephestia kuehniella
- Tobacco Moth, Ephestia elutella
- Webbing Clothes Moth, Tineola bisselliella
- Black Carpet Beetle, Attagenus unicolor
- Brown Carpet Beetle, Attagenus elongatus
- Cigarette Beetle, Lasioderma serricorne
- Hide Beetle, Dermestes maculatus
- Furniture Carpet Beetle, Anthrenus flavipes
- Guernsey Carpet Beetle, Anthrenus sarnicus
- Larger Grain Borers, Rhyzopertha dominica
- Lesser Grain Borer, Prostephanus truncatus
- Red and Confused Flour Beetles, Tribolium spp.
- Varied Carpet Beetle, Anthrenus verbasci
- Warehouse Beetle, Trogoderma spp.
Longevity of pheromone lures
It is important to contact the pheromone manufacturer to determine the shelf life, duration of pheromone release, recommended spacing of lures, production dates and general composition (e.g. blended pheromones). This will ensure consistent, long-term release and attraction to the lures by insects. Poorly made products will gather poor results. Cheaply made lures have very little pheromone, no control over release rates, are poorly packaged, and are often left on retail store shelves for many months. Check newly ordered products to ensure that their shelf life has not expired by the time of purchase.
Aside from sticky traps and pheromone lures what other traps can I use to identify pest problems in my collections?
Other trap types for storage areas:
- Dermestid larval monitors can be used to see if larvae are present. If you do find that larvae are present, then you know that you have a breeding population within the storeroom. The larvae are not strong enough travelers to come in from the outside. Generally, the source of the larvae will be within a 10 foot radius from larvae found in the monitors.
- Light traps can give you lots of info relatively quickly. These can be particularly effective with native carpet beetles, which are attracted to light and often found near windows. Light traps must be placed so that the UV light is directed away from any sensitive collections such as textiles, and not shining out of any window.
Responding to a Potential Disasters: Moths in the Ethnographic Collections at the American Museum of Natural History, poster presented at the 2017 SPNHC Annual Meeting describes how pheromone traps were useful in the monitoring program after a large infestation was discovered.