What lures a potential partner? While it may be looks and charm in humans, for insects it is typically a seductive chemical.
You may have heard of pheromones – chemical attractants.
Scientists have identified pheromones for more than 1,500 insects, although only a small number of them are used commercially.
Read on to learn about the many ways you can use these hormones to control insect infestations as part of your integrated pest control strategy.
Using pheromones in the garden
What is a pheromone?
A pheromone is a specific chemical that insects and other organisms use to communicate with others of the same species – usually those of the opposite sex.
Once released, the pheromone travels through the air or water before reaching the second organism, which will often change its behavior in response.
These chemicals are usually used to lure a mate, mimicking pheromones released by females, but some species warn of danger.
Pheromones are active at extremely low concentrations, just 1 millionth of an ounce.
Since their discovery in 1959, chemists have learned to synthesize many in large quantities. This allows them to be widely used, mainly in traps.
The ability to lure insects into traps has been a boon to growers and other people who are regularly threatened with insects.
Use in surveillance traps
One of the most common uses of pheromones is in lure traps.
Common pests
Sticky traps coated with these compounds are placed in a field or orchard before the target insect has become active.
Then you check them daily for the presence of the insect. Once the insect is identified, you know to closely monitor its levels.
By keeping track of the number of males you find each week, you can track the development of the population over time.
One way you can use this information in your pest control planning is to record the date of first arrival in your garden diary and use a degree-day model to predict when populations will grow so large that you need to take action (e.g. spray them with insecticides).
Photo by Howard F. Schwartz, Colorado State University, Bugwood.org, via CC BY-SA.
State and university information offices often provide this information so that you can use your data to make pest control decisions.
Other types of pests that are commonly controlled include:
Cockroaches Stored grain pests in distribution centers or warehouses
In addition, monitoring traps are used nationally to track the spread of pests such as gypsy moths and Japanese beetles.
Emerging Threats
In other cases, pheromone traps are used to determine whether potentially invasive insects, such as those in quarantine, have entered an area.
An example is the Asian citrus psyllid, which fills citrus growers and stakeholders with fear.
This insect is a vector for the citrus greenery pathogen, which has devastated Florida’s citrus industry and put California on high alert.
Another is the Mediterranean fruit fly.
Ports of Entry in the US
Many invasive and destructive pests have entered the US in cargo containers or the wood packing material in ships.
With approximately 25 million freight containers entering the US each year, researching all of this cargo is an incredible undertaking.
The U.S. Customs and Border Protection Service employs agricultural specialists who work in 167 ports of entry — sea, land, and air — along with their canine assistants.
Cue pheromone traps! They are used at most major ports of entry in North America to identify invasive insects that could pose a threat to U.S. agriculture.
Disruption of mating
This strategy confuses the males by filling the air with these chemical attractants.
The presence of an excessive amount of pheromone means that the males cannot locate the females!
And that’s why they can’t mate.
This has been an effective technique for drastically limiting the populations of some types of insects and reducing the need for insecticides. In some cases, pests have been eradicated from certain places.
These types of systems are available for orchard pests such as oriental codling moths, codling moths, peach tree borers, small peach tree borers and dogwood borers.
Complications of this strategy
Biological systems are complicated by nature and the use of pheromones is no exception.
Collateral damage
A reduction in insecticide use to eradicate the primary pest can sometimes lead to outbreaks of other types of pests that were also controlled by a particular insecticide.
There are two common examples in orchards:
1. Oriental codling moths in peaches – Their elimination has led to more stink bug injuries.
2. Codling Moths in Apples – A common side effect of reduced pesticide use is an increase in leafrollers.
Greater difficulty in smaller fields or orchards
Efforts to disrupt mating are more effective in fields or orchards larger than five acres, so this may not be a good strategy for a homeowner with only a few trees.
Also, if the crops or orchards are adjacent to others that are not being treated, the treatment will be less effective.
Disruption of surveillance
If the air is flooded with pheromones, the males will not only have trouble finding mates, but will probably be unable to find the traps.
Sprayable pheromones
In this case, the pheromones are stored in a polymer capsule, which controls their rate of release.
You can spray these formulations through the air like conventional pesticides, and they usually last 4-6 weeks.
You may need to reapply it several times per season.
The most effective on the market targets the Oriental codling moth.
Hand-applied dispensers
Hand-applied dispensers have a reservoir with an impermeable membrane that regulates the release of the pheromone.
These dispensers are draped, flipped or twisted directly onto the plant.
The labor involved can get expensive for a large field or orchard, but it is more feasible for homeowners.
In some cases, its use can suppress mating for an entire growing season.
Removal of insects from an ecosystem
Another use of pheromones is to catch large numbers of insects that pose a serious threa
You may have read about the serious damage bark beetles do. In California alone, CalFire reported in 2017 that more than 102 million trees had been killed by bark beetles to date.
This damage has devastated forests, leaving large amounts of brittle, dead trees that burn like torches. In some places, as much as 85% of the trees have been killed.
Pheromones have lured millions of bark beetles into traps and away from trees.
Where to buy
Arbico Organics offers a variety of lures and pheromone traps.
Scentry large plastic delta trap
The reusable Scentry Large Plastic Delta Trap is suitable for all types of insects and pheromone baits are sold separately.
Simply add the lure to the trap to easily track pest populations and disrupt the mating cycle.
These hard-wearing traps are designed to withstand adverse weather conditions.
Find packs of 5 or 10 available from Arbico Organics.
Scentry wing traps
Suitable for a variety of insect pests, the Scentry Wing Traps are weather resistant and work well in orchards and greenhouses, as well as among vegetable crops.
The bottom of the trap has a grid pattern to make counting caught insects easy.
Pheromone attractants are sold separately and your choice depends on the insect you are targeting.
Find packs of 5 or 10 and replacement bases available from Arbico Organics.
Pheromone Lures
Your choice of lures will depend on the insect species you are targeting.
Both traps can be used with bait for a variety of insect pests, including armyworms, cabbage loopers, clear-winged peach tree borers, pumpkin borers, and many others.
Check out all the lures available at Arbico Organics.
Scentry Gypsy moth traps
This half-gallon trap is specifically designed to capture adult gypsy moths and helps monitor the gypsy moth population in an area.
Easy to assemble, the lure is placed in the trap in early summer. Pheromone attractants are sold separately.
Find the gypsy moth trap at Arbico Organics.
Tips for pheromone users
Doug Johnson of the University of Kentucky Department of Entomology offers some practical tips for using pheromone traps in field crops:
1. Be sure to label the trap with the name of the species and the date the bait was replaced.
2. Change the bait once a month
3. Do not leave bait packages or used bait near your traps. They can compete with your bait.
4. Wash hands between handling baits or wear rubber gloves to prevent cross contamination.
5. Be sure to remove and dispose of trapped insects during each visit from your field or orchard.
It’s all about hormones
While such statements may be an insult to humans, it is absolutely true for insects.
These powerful chemicals can lure male insects into traps to alert you to their presence so you can take action
And in some cases, flooding the sky with them can greatly disrupt the mating process.
Pretty dramatic results for a compound present at one millionth of an ounce!
Have you had success using pheromones in your garden? Let us know in the comments below.
And to learn more about how to control pests in your garden, you’ll need these guides: