Pheromone Traps

Pheromone traps use chemicals to trick insect pests.

We all know that smell is a powerful trigger for many species. Smell is why we are drawn to freshly baked bread, why we are soothed by lavender and vanilla, and why we wear cologne and perfume. The chemicals that stimulate these and many other responses are called pheromones.

Pheromones are chemicals that stimulate a response within a species. Since most insects only live for a single season, reproduction is critical to species survival. Insects frequently use pheromones to find each other. Pheromones are categorized according to the response they stimulate: 

• sexual pheromones tell males that there are receptive females nearby
• aggregating pheromones attract both genders
• alarm pheromones send insects running away

Sexual pheromones

Most over-the-counter pheromone traps are of the sexual variety. They use synthetic female pheromones to attract males. Chemical signals loft into the wind and are picked up by sensory receptors on a male insect’s antenna. He follows the trail in search of love. What he ends up finding, in most cases, is a paperboard tent lined with a deadly stickum, right next to a little tab of luscious pheromones. In other cases, he may find a tray filled with powdered female pheromones. He joyfully rolls in it, finds nothing, and flies away - smelling like a female. Alas for him, in either case.

What pheromone traps can and cannot do

Pheromone traps interrupt mating. They do this by confusing the males with all the extra aromas and by trapping them on the sticky goo. Contrary to packaging claims and popular opinion, pheromone traps are not effective at eliminating a specific type of pest. In fact, they can do just the opposite! Your lone apple tree may have skirted a codling moth disaster until you hung a pheromone trap in it. Suddenly, every codling moth on the block wants to party at your house!

Proper use of pheromone traps

To be effective, pheromone traps are used to monitor specific areas for invasive or particularly destructive pests. Pheromone traps to help you to determine the best time for particular treatments.

How to use pheromone traps

Since pheromone traps are species specific, you must first identify the pest you are trying to monitor. Next, you need to learn the best time of year to employ pheromone traps. These tips can help you make the most of pheromone traps:

• traps should be placed in the same location each year
• use more traps in heavy infestation areas
• traps should be hung 6 to 8 feet above ground, in shady areas, preferably 1 to 3 feet inside the canopy in the northern quadrant of the tree
• traps should be inspected twice a week 
• record and remove trapped insects

As the number of trapped insects changes, you can see become more aware of the rise and fall of breeding populations. This provides you with the information you need when deciding on which insecticide or other treatment plan is best suited to your garden or orchard. [If you feel like getting really technical, you can also calculate degree days for more effective information.]

Insects monitored using pheromone traps

Since reproduction is so important to short-lived species, pheromone traps continue to be an effective monitoring device for a large number of insects. Some of the most troublesome insect pests that are monitored using pheromone traps (during specific time frames) include:

• armyworms
• artichoke plume moth
• citrus leafmining moth
• codling moth (budbreak; late March to early April)
• navel orangeworm moth (mid-March)
• obliquebanded leafroller (early fruit set; mid-April)
• omnivorous leafroller (just before budbreak)
• orange tortrix (late December)
• stinkbugs (early April)
• peach twig borer (March 20 - April)
• peach tree borer (April - September)
• San Jose scale (February 25 - March 1)
• vine mealybugs (April - June)

Crops best suited to pheromone trapping

Pheromone traps do not provide benefits to all crops. The most common applications of pheromone traps include:

• apples
• almonds
• apricots
• grapes
• pears
• prunes
• walnut

Don’t be put off by this shift from quick-fix solution to data collection and informed decision making. The extra knowledge and effort can spell the difference between hosting a party of undesirables or producing an abundant crop of delicious food.