Potted plants that spend their summers outdoors are often prone to pest outbreaks when they're brought back inside for the winter. Though there are many different pests that can piggyback their way indoors on these plants, few are as annoying and tenacious as whiteflies.
Whiteflies do not typically survive the winters outdoors here in Pennsylvania, but in the South, where freezing temperatures are not the norm, whiteflies are year-round pests of many different garden plants, including tomatoes, lantana, nicotiana, geranium and many others.
These tiny, white, moth-like flies are a mere 1⁄10 of an inch long, and their wingless nymphs are even smaller. They're barely noticeable when there's just a few around, but once these insects are present in large populations, they're hard to miss. They breed quickly, so when outdoor plants are moved indoors, the population can quickly explode.
Many times whitefly infestations start at the nursery where you purchased the plant. Greenhouses remain warm year-round, and unless they've been intentionally introduced as part of a pest control program, they have a lack of natural whitefly predators, creating the perfect breeding ground for this pest.
The warm, humid environment of a greenhouse is an excellent starting place for an infestation. Because they're so small, if you purchase a plant with just a few whitefly nymphs on it, you wouldn't even know they're there. The first step in preventing an infestation is to carefully inspect any plants you purchase before you bring them home.
That being said, whiteflies can also spread very quickly from an infested plant to a “clean” one throughout the summer months. They can fly over from your neighbors or be carried on the wind from a good distance.
Outdoors, whiteflies seldom cause much damage as there are natural predators around that help control them. However, occasionally they do get out of hand and cause leaves to yellow and fall off.
Whiteflies suck sap from plants and, when an infested plant is disturbed, a flush of small, white flies quickly emerge from the plant.
If any of your overwintering houseplants or tropicals have whiteflies, you'll need to put the plant in the bathtub and treat it with horticultural oil or insecticidal soap. Be sure to apply it to the lower leaf surfaces as well as the upper, because this is where whiteflies tend to congregate. Follow all label instructions carefully.
You can also put yellow sticky traps (available online) just above the plant tops. These yellow cards are coated in a non-drying glue. Many common pest insects are attracted to the color yellow, including whiteflies. They'll fly up to the card and get trapped in the sticky glue.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to tribliving@tribweb.com.
