Biological control against pest insects is all the rage, and pheromone traps are proving to be effective and natural solutions. Previously, only professionals would use these traps. But they’re slowly are making their way into family gardens and orchards.
Note that a single trap can’t protect against all attacks. Here, you’ll read how and when to use these special kinds of traps.
Before understanding what a pheromone trap is, let’s dive back to our schoolday lessons. Remember what pheromones are? No? Here’s the answer: they are chemical molecular substances produced by animals, especially insects. In a word, “scents”. They essentially allow them to communicate and send messages to other individuals of their species.
For insects, key pheromones trigger interactions between males and females to enable mating and reproduction. Other pheromones are related to territory, while others still broadcast the presence of interesting food. Another set of scents transmit alert messages when danger lurks…
In biological control, the most effective lure are sexual pheromones. These are used in traps. In practice, the traps release fake, synthetic pheromones, that would normally be secreted by females during mating season to attract males . Males are therefore tricked and trapped instead of meeting up with females.
Without males, females can’t reproduce. For species with high reproduction rates, traps greatly reduce numbers for that generation. Furthermore, these traps allow gardeners to know when the breeding period begins and ends.
There are two types of pheromone traps:
There are also chromatic traps, often yellow or blue. These two colors attract certain insects.
Not every trap catches in the same way: some drown the insect, some glue it down, and one works by colour rather than scent. Here is what the article describes.
| Trap type | How it catches | What it is used for |
|---|---|---|
| Funnel or water trap | Capsule in a lidded funnel filled with water; males drown, exhausted by their flight | Flying males drawn in by the scent capsule |
| Sticky plate or delta trap | Triangular, tent-shaped device with a sticky plate as its floor; males stick to it | Flying males drawn in by the scent capsule |
| Collar-shaped trap | Fitted as a collar around the trunk | Placed around trees against processionary caterpillars |
| Chromatic trap | Attracts by colour rather than scent, often yellow or blue | Certain insects drawn to those two colours |
Whichever model you choose, the capsule is the consumable part and the trap itself is reusable year after year.
Widely used in organic farming, pheromone traps offer many advantages:
The only disadvantage they have is that they’re actually good at annihilating a pest species. Yes, you have to be a very zen gardener!
Indeed, one could argue that even insects who eat our fruits and young vegetable shoots are also useful and contribute to the great cycle of life. Other gardeners prefer to trust helper fauna by planting plants that attract birds, certain mammals like hedgehogs, or reptiles such as lizards.
There are different types of pheromone traps, specific to particular species. In general, it’s primarily butterfly (Lepidoptera) and fly (Diptera) that are targeted.
Pheromone traps must be placed as close as possible to vulnerable plants to be fully effective. Therefore, in a vegetable garden, the trap is set among the vegetables, about 2 feet (60 cm) above so that insects get trapped during their flight.
In the orchard or decorative garden, pheromone traps are hung in the heart of the tree, at a human’s height.
The number of traps needed varies. It is generally easy to compute from information on the packaging.
Herein lies the main difficulty! Indeed, when to install pheromone traps is entirely dependent on the breeding period of each insect. But, in general, they are set from the early months of spring, when the temperature is sufficiently warmed. It is indeed at this time that insects emerge from hibernation to fly.
For fruit trees, it is advised to wait until the end of blooming so as not to disturb pollination.
They should remain in place until the end of summer since some insects have multiple generations. Generally, pheromone capsules inserted into the traps work for 4 to 6 weeks. Therefore, plant to replace them after that span of time.
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