Love Trap for Bugs

A pheromone trap is an insect trap in the form of a box, bottle, or bag containing pheromones (chemical substances similar to hormones) that attract the insect you want to prevent. Pheromones can mimic the scent of the insect’s favorite prey (fruit, flowers, etc.), but often the pheromones used in traps are a little more daring than that: they mimic the insect’s sex pheromones, usually those of the female. This attracts males from far away, lured by the scent of what they believe to be an attractive young virgin. Once inside the trap, the males are trapped and unable to fertilize the females, which, in theory, will cause the insect population in the area to decline.

Note that, for added appeal, the trap is often yellow, blue, green, or purple, depending on the insect’s preferred color.

A Trap for Every Insect

Pheromone traps are highly specific: each one targets a particular type of insect. They do not catch any other insects, especially beneficial insects. You should therefore buy them according to the specific type of insect you are concerned about.

For now, at least in Canada, the most commonly available trap is for Japanese beetles (Popillia japonica). It contains two pheromones: a sex pheromone that mimics the scent of female Japanese beetles, attracting male beetles, and another that gives off a floral scent that attracts both sexes.

Incidentally, because of the floral scent of the pheromone, the Japanese beetle trap will also attract rose chafers (Macrodactylus subspinosus), but there is also a trap specifically for rose beetles that contains only the floral scent. However, this is more difficult to find in stores.

Apple fly traps are also available on the market, usually in the form of red balls containing a fruity pheromone: a fruit essence that attracts apple flies.

While amateur gardeners have only a limited choice of traps, farmers and foresters have access to a wide range of pheromone traps designed for an equally wide range of crop pests. You may notice, for example, traps placed in ash trees (Fraxinus spp.) in a park in your municipality. These traps are used to determine whether the dreaded emerald ash borer (Agrilus planipennis) is lurking in the area.

Trap Failure

But there is one major flaw with pheromone traps for controlling pests: they attract insects from the surrounding the area, but not all of them enter the trap! Either they fly past it or the trap is already full.

This means that the presence of a trap often makes the situation worse, as the insects that are not caught, now hungry, rush to the available plants and start eating them. This is particularly the case with beetle traps: lots of beetles are caught, but this does not reduce the damage.

However, you can use the trap effectively if you follow three simple rules:

1. Place the traps away from plants that are eaten by insects (at least 15 m/50 feet away). For example, on a post in the middle of a lawn.
2. Empty the traps regularly. This may need to be done every day, otherwise they will fill up and new insects will not be able to enter. Simply throw the harmful insects into a bucket of soapy water.
3. Go over the area daily, preferably early in the morning when the beetles are less active, with a handheld vacuum cleaner to collect the insects from nearby plants (empty the vacuum cleaner into a bucket of soapy water). Children, in particular, seem to find collecting beetles with a vacuum cleaner great fun.

If you start using this combined method at the beginning of the season, you can significantly reduce the infestation.

This text was first published on this blog on July 20, 2015. It has been revised and its layout has been adapted.