The Detractors: Factors that can hinder a successful pheromone monitoring program
Written By: Patrick Kelley, BCE, President of Insects Limited
The benefits of a pheromone monitoring program are quite well defined. When used correctly, pheromones can;
1. Give an early indication of pest species before damage or loss occurs
2. Pinpoint the sources of pest activity in large areas, and
3. Relay information on whether the steps taken to reduce pest activity are working.
This article isn’t about the benefits of a pheromone program that we know to be true though.
Instead, it will focus on some factors that can hinder a successful monitoring program. It should be made clear from the start that all the detrimental factors listed here can be overcome with proper training on the best practices for implementing a pheromone monitoring program.
““… all the detrimental factors listed here can be overcome
with proper training on the best practices for implementing
a pheromone monitoring program.””
To understand why, in some situations, pheromone monitors don’t perform to the best of their ability, it is necessary to first understand how pheromone lures work. Pheromone lures and attractants used for monitoring purposes rely on precise biological responses from insects and in return, the insects supply vital information about their population size and location.
Sex pheromones, aggregation pheromones or food attractant kairomones can also be used to draw stored product insects into a monitoring trap.
Listed below are a handful of instances of human error or environmental conditions that can hinder the effectiveness of a monitoring program, rendering the lures ineffective and preventing usable information from ever getting to the IPM technician.
A. Human Error: Instances of human error causing a monitoring program to be less effective. This first set of detrimental factors listed here can be attributed to either misinformation or a lack of knowledge by the applicator who is implementing the program.
1. Species Misidentification: Like a lock-and-key analogy, pheromones are species-specific, meaning that an insect will only respond to their own pheromone and not to other species pheromones. If a misidentification of the pest species occurs, and the wrong pheromone lure is placed out, it will not be effective. E.g., if an Angoumois grain moth is misidentified as an Indianmeal moth, the Indianmeal moth pheromone placed out will never attract the Angoumois grain moth flying around.
2. Incorrect Trap Placement: Placing the traps in the wrong location can result in reduced effectiveness. They should be positioned where the target insect species are most likely to be present. E.g., a trap for crawling beetles placed in the center of the room away from any walls will rarely capture a beetle.
3. Incorrect Trap Design for the species of insect: The design of the trap may not be suitable for the target insect species or may not effectively release the pheromones to attract them. E.g., a trap for crawling beetles hung, suspended in air will never capture a beetle.
4. Lack of Trap Maintenance: Lack of proper maintenance, such as cleaning the traps regularly or replacing damaged components, can reduce their effectiveness over time. E.g., sticky traps in dusty areas rapidly lose their tackiness allowing insects to enter and exit the trap without being captured.
5. Glue Saturation: If the local insect population is high, the glue adhesive in the traps may become saturated with captured insects, making it difficult to capture additional insects. Traps greater than 50% of the adhesive surface covered with dust or insects should be replaced.
6. Pheromone Output: Pheromone lures that have exceeded their recommended life in the trap are much less effective or not effective at all. Pheromone lures need to typically be replaced every 90 days or they may not be attractive at all.
7. Pheromone Lure Storage Conditions: Pheromones are highly volatile chemicals that can evaporate quickly when stored in exceptionally hot areas such as in direct sunlight, within hot vehicles and in areas with no climate control. Over time, sunlight or high temperatures can break down or change the insect pheromone, rendering it ineffective.
8. Air Saturation of Pheromones: A pheromone trap competing with large quantities of pheromone in the air from mating disruption products or from an excessive amount of pheromone traps placed in a small area will capture less insects simply because it is harder for an insect to locate the source of the pheromone.
9. Not Allowing the Traps Adequate Time to Work: Checking a trap that has only been placed out for a short amount of time may yield low capture numbers simply because the insects have not had time to locate the trap to be captured.
B. Instances of Environmental Conditions causing a monitoring program to be less effective. The following factors related to environmental conditions can contribute to reducing the effectiveness of a monitoring program for stored product insects.
10. Extreme Temperature: Most stored product insect pests do not actively fly or crawl around in temperatures <65°F/18°C degrees. With cooler temperatures, the insects will move less and thus will not end up in traps. When it becomes too hot (>95°F/35°C), the insects can also shut down on movement to preserve energy.
11. Competing Odors: Odors in the environment, such as nearby food products, can draw insects away from traps and towards those food sources. Factors that can come into play as to whether an insect prefers to feed or look for a potential mate at any given time can include its age and how well fed it is as well as the temperature and relative humidity in the environment. Strong chemical odors can also negatively affect how well a pheromone lure might work.
12. Overpowering Air Currents: A pheromone plume emanating from a lure will follow any air current blowing across it. Insects follow these pheromone plumes back to the source in a trap. If a lure and trap are placed in an area of high wind velocity, the insects attempting to reach the trap cannot physically make it without being blown away. Strong air currents also jumble the pheromone plume, making it impossible for an insect to locate the source.
Another common problem with air currents is when a lure/trap is placed too near to an air intake vent as part of the HVAC system within a structure. The pheromone plume coming off the lure will never make it to where the target insects are located since the plume is pulled directly into the HVAC system and mixed with other air at a high velocity.
13. Insect Population Dynamics: Changes in the population dynamics of the target insect species, such as fluctuations in population density or behavior, could affect their response to the pheromone traps. Also, sex ratios of pest insects often fluctuate, which will lead to times where a high number of adult females are flying around that are unresponsive to a pheromone lure.
14. Timing: Pheromone traps must be deployed at the appropriate time in the insect's life cycle to be effective. Pheromone traps only attract adult insects. If all of the target insects are in the larval stage and actively feeding on food product, no adults will be found in the pheromone traps. If they are set up too early or too late in the development of the insect, they may not capture any insects at all.
15. Other Environmental Factors: Ongoing construction or demolition in areas where the traps are placed, movement of infested products, dock doors being opened and shut, and other environmental factors could alter the behavior of the target insects and their response to pheromone traps.
By thoughtfully considering the above factors that can reduce effectiveness, pheromone monitoring programs can be smoothly implemented. When implemented thoughtfully, monitoring programs will continue to supply pest managers with ongoing information that will allow them to make the best-informed decisions on pest management.
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Insects Limited, an Insect Pheromone Company
Insects Limited, Inc. researches, tests, develops, manufactures and distributes pheromones and trapping systems for insects in a global marketplace. The highly qualified staff also can assist with consultation, areas of expert witness, training presentations and grant writing.
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