Check your indoor plants for whitefly insects before they get out of hand

I check most of my plants nearly every day to see how they are faring. I monitor soil moisture, growth progress and signs of disease or insect problems.

A couple of days ago, I spotted a moving tiny wisp of white rising up from a pepper plant that I had dug up last fall and was overwintering.

That bit of white was a single tiny flying insect. Looking closer, I saw that there were several more. When I tapped on the plant, even more briefly flew up from the plants then settled back down again. I knew immediately that I was looking at whiteflies, a common insect pest found in greenhouses and many indoor plants.

Fully grown whiteflies are only about 1/10th of an inch long. One individual, or even just a few, will cause no immediate harm to a plant. The problem is, is that they reproduce exponentially. Since each female lays 50 to 400 eggs, you can see how one whitefly will turn into hundreds very quickly until you end up with thousands of them.

During reproduction, whiteflies go through a typical insect metamorphosis life cycle. Shortly after the adult female lays her eggs, they hatch into a nymph stage called “crawlers.” The crawlers crawl from their hatching spot and settle down to feed and stay in that exact new spot. That stage is called the “scale” stage. They eventually pupate and finally emerge as an adult.

Whiteflies cause plant damage by their feeding habits. They poke their beaks into a leaf’s phloem, inject digestive enzymes and suck out the plant sap. In that manner, hundreds of whiteflies will cause serious damage to plants, even to the point of weakening them so much that the plants die. Adults as well as the nymph stages feed in this way.

Plant sap is highly diluted. For example, think of how much maple sap is needed to produce maple syrup. Whiteflies and other sap feeding insects require large amounts of sap in order to get the nutrients they need to sustain themselves. They cannot use the excess sugar in sap so they excrete it as a sweet syrupy waste product called honeydew. In turn, the honeydew often gets covered by sooty mold causing an unsightly mess.

In the wild, whiteflies are tropical insects and as such, cannot survive freezing temperatures. It’s winter, so where did my whiteflies come from? My thinking is that they were present on some plants that were growing in my large citrus tree pots. I brought the potted trees in last fall and placed them in a semi-heated spot.

Under warm temperatures, above 70 degrees F, whiteflies can complete their life cycle in as little as three weeks. However in cool conditions, under 50 degrees F or so, they slow down and it can take several months for them to go through their life cycle.

My citrus trees were in a very cool space all this winter so that meant any whiteflies present would be significantly slowed down. It's possible during watering I may have picked up a whitefly or two on my fuzzy wool sweater and transported it to the warm room where they woke up and made a bee-line to the pepper plant and started to reproduce there.

Whiteflies almost always lay their eggs on the underside of the leaves. Since the whitefly itself is so small, you can imagine how tiny the eggs are.

They have a distinct way of laying their eggs. Instead of flitting from leaf to leave like you might think, they instead lay their eggs right where they are feeding. As their beaks are inserted to the leaf for feeding, they will lay eggs at the same time. After each egg is laid, the female moves slightly to the side and lays another egg. As this continues, the eggs end up being laid in a ring pattern.

You can control whiteflies with a series of methods.

The first line of defense is to wipe the leaves with a damp, soft cloth to remove and/or destroy the crawlers and scale stages.

Use a household vacuum to catch the flying adults. It’s fairly easy to suck them up since they are not very strong fliers. A light tap to the branch will send the adults into the air so you get them.

Yellow sticky traps can be purchased at garden centers and used to catch some of the adults. The yellow color of the traps is attractive to many flying insects including whiteflies. The color lures them to fly onto the surface of the trap where they get stuck. The traps will not catch all of the adults but will catch some while you are away from your plants.

If they are getting out of hand, spray them with an insecticidal soap.

Check your plants soon and often. The earlier you start with your control measures, the easier it will be to keep the whiteflies in check.