Everyone knows that insects are attracted to light: you just have to go outdoors on a warm night to see them turning round and round an electric bulb. Few people know, however, the light traps are widely used in restaurants and stables to catch flies, mosquitoes and other flying insects… or that they will also work in controlling houseplant pests.
The light traps in question are wall units that contain black light fluorescent tubes and a replaceable yellow sticky card. The insects are first attracted to the light, then to the yellow sticky card, and end up sticking to the latter. You just have to change the sticky cardboard every few months. (I do it about twice a year.) These traps are very effective indoors, where all insects are intruders. They will effectively control whiteflies, fungus gnats, house flies, fruit flies, thrips, mosquitoes, moths, and almost any other flying insect that dares to enter your home. They’ll be of no use, of course, against crawling insects like mealybugs or scale insects.
You do, however, want to place such a trap well away from openings to the outdoors (doors, windows, etc.), otherwise they will tend to attract insects into the house. These traps are not as useful outdoors because they attract as many beneficial insects as they do pests. Also, they’re a costly solution (these lamps are not cheap) but at least they completely solve your flying insect problems.
I used to live in perennial fear of the annual spring whitefly invasion, where the nasty little creatures seemed to generate spontaneously each spring to coat my houseplants and seedlings. Now whiteflies are a thing of the past: the control with my light trap is 100% effective… and how many times can you say the same thing for any insecticide treatment?
Where to Buy Them?
For such a remarkably effective cure to a remarkably common problem, light traps are remarkably hard to find. I’ve never seen them in a garden center (where you’d think they’d be front and center during the spring whitefly invasion), for example. Hardware stores sometimes sell small plug-in models that might work (I haven’t tried them… because, indeed, I have no need to: I no longer have a flying insect problem!), but the “real McCoy”, the traps you see in restaurants everywhere, just aren’t sold in retail stores. Try an exterminator or a supplier of products for restaurants or stables.
Bring your credit card and bite the price bullet (I nearly had a heart attack when I first saw the price!). I finally found used one in a flea market for $50… and it is still functioning 22 years later. I’ve only had to replace the black light tubes once and I’m still working on my initial pack of replacement sticky cards. Money well spent, in my opinion!