How to Identify and Manage Whiteflies

Whiteflies were never a common pest in the interior landscape, but with some of the newer invasive whitefly species we now have in the US, they have become a bigger issue.

Whiteflies are easy to recognize because they look like their name, although they’re not truly flies. These little insects do their damage by sucking the sap from plants, producing honeydew, and leaving waxy filaments. Furthermore, they are a visual nuisance, so let’s talk about how we can protect our plants.

Why Are Whiteflies So Destructive?

Whiteflies have piercing mouthparts they insert into plants to feed on the sap. They excrete honeydew, and when whiteflies are in abundance, this can become an issue because it leads to sooty mold which diminishes plant health.

How to Identify Whiteflies

Adult whiteflies are soft-bodied insects that have white wings with a yellowish body. When disturbed, they will often fly off the plant. The adult females lay their eggs on the underside of leaves, sometimes in a circular pattern. Whitefly nymphs are oval, yellowish, and can have white waxy filaments (not legs) around the body.

The Life Cycle of a Whitefly

In warm temperatures, whiteflies develop quickly. Adult female whiteflies lay between 200 and 400 eggs, in a circle or spiral pattern. The pattern depends on the specific species. About a week after being laid, the eggs hatch into crawlers that disperse on the plant. The crawlers then insert their straw-like mouthparts and extract plant juices. After feeding, they pupate, and a new whitefly emerges. How long it takes for the whiteflies to develop from eggs to adults varies with species, but on average it is 4 weeks.

Do You Have a Whitefly Infestation?

CLEAR INDICATORS:

• White gnat-looking insects flying near plants
• Dropping and yellowing leaves
• Stunted or distorted growth
• Presence of whiteflies on yellow sticky cards
• Appearance of sooty mold

It’s Time to Take Back Control

Before proceeding with any treatment, it is important to confirm the presence of whiteflies on your indoor plants. If whiteflies are, in fact, present, the removal of infected plants is the first option. There are biological control agents for some whitefly species, but many of these beneficial insects fly, and your clients probably do not want to have anything else flying around their interior landscape. A better option would be to treat with products like insecticidal soap or horticultural oil. For soaps and oils to work, you must spray the underside of the leaves where the whiteflies are located.

Chemical insecticides like Safari (dinotefuran) and Flagship (thiamethoxam) can be used as a drench on the interior and are very effective. Another option is Endeavor (pymetrozine). This is a foliar-applied insecticide that paralyzes the mouth parts of whiteflies, preventing them from feeding.

Pest control labels vary between states and the pesticide user bears the responsibility of consulting the pesticide label and adhering to the law. Always read the label before applying a pesticide to make sure it is legal to apply on your site, in your state, and to the plant material.

Preventing Whitefly Infestations

Seasonal plants like poinsettias are particularly susceptible to whiteflies, and they serve as excellent hosts. If you do see whiteflies on poinsettias, it may be best to replace the plants altogether because treatment can be tricky once the plants are in color.

If you’re dealing with adult whiteflies, yellow sticky cards can be a lifesaver. These cards are specifically designed to entice whiteflies with their yellow shade, making it easy to trap them. This method not only helps capture adult whiteflies but also determines if they are present in the vicinity.

Battling other common indoor plant pests? Check out my Professional’s Field Guide to Plant Pest Control for information on spider mites, thrips, fungus gnats, mealybugs, aphids, and scale insects.

Featured image by Fluffymuppet via https://www.flickr.com/photos/fluffymuppet/4904738679/