You might have seen a swarm of white gnats around your houseplants. Or maybe there’s a swarm around your perennials. If you find your plant’s leaves browning or curling, you may be certain that these white gnats are the cause.
The term “gnat” refers to a wide range of flying insects. So, to actually rescue your plants, let’s go over how to determine which insect species are bothering your garden. From there, you can learn about how to get rid of your specific variety of white gnat.
Species of white gnats
When it comes to identifying the species, you’re most likely dealing with whiteflies or woolly aphids.
First, let’s discuss whiteflies. Despite their name, whiteflies are more closely related to aphids than flies. Whiteflies are classified as Hemiptera insects, and their name comes from the white wax that covers their bodies and wings. Whiteflies enjoy warm weather and can thrive in areas where their natural predators are absent.
Second, there are woolly aphids. These little insects were named because the white, waxy excrement they generate. As the aphids wander about, the wax coats them, giving them a fuzzy appearance. Woolly aphids enjoy eating sap from trees such as pear, ash, oak, elder, and elm. They also appreciate veggie and beautiful gardening.
Life cycles
Whiteflies lay eggs on the underside of leaves, which hatch between six to ten days. When the eggs hatch, little nymphs emerge. The nymphs are flat and oval in shape, with a cottony texture all around. Nymphs go through four developmental stages known as instars.
After 18-22 days, a winged whitefly adult emerges from the final nymphal stage. Adults are just approximately two to three millimetres long and can live for 30-40 days. At every stage, the whitefly feeds by sucking plant liquids from the leaves.
The woolly aphid has three primary developmental stages: egg, nymph, and adult. Woolly aphids go through four instars as nymphs, becoming larger and larger until they mature into adults. Adults range in size from one to three millimetres, depending on the species, and live for approximately 30 days.
Identification
Although you are most likely dealing with a whitefly or woolly aphid, there are numerous kinds of both. As you are aware, each species is attracted to different types of host plants and has varying migration abilities. It may be useful to know the type of whitefly or woolly aphid you’re about to confront
There are two main whitefly species
There are two main whitefly species to watch for: the sweet potato whitefly and the greenhouse whitefly.
The sweet potato whitefly loves a variety of herbaceous plants (those lacking a woody stem above ground). However, the sweet potato whitefly can infest woody plants as well. Cotton, tomatoes, peppers, crape myrtle, roses, and hibiscus are some common examples.
This variety of whitefly can be identified by looking at its nymphs in the fourth stage of development. They have no waxy filaments and little fringe surrounding their oval-shaped bodies. As adults, sweet potato whiteflies have white wings and a yellow body, with their wings slightly inclined to the surface.
The greenhouse whitefly prefers a wide variety of host plants, including most vegetables and herbaceous plants. Avocados, lantanas, and redbuds are a few examples.
When hunting for this variety of whitefly, seek for nymphs in the fourth stage of development with long, waxy filaments and fringe. Adults have white wings and a yellowish complexion. They keep their wings straight out, resembling a triangle.
The University of California Agriculture and Natural Resources’ identification table provides a comprehensive list of all whitefly species and features.
There are two main woolly aphid species
The two primary species to search for are the woolly apple aphid and the woolly elm aphid.
The woolly apple aphid forms groups on the bark, leaves, roots, and fruit of an apple tree. However, they prefer hawthorn and pear trees. When they feed, they produce galls (abnormal growths) on the bark, trunks, and branches. As adults, they measure between 1.2 and 2.5 millimetres long.
Woolly elm aphids are two to three millimetres long as adults and mostly feed on elm trees and hawthorns. They can be found on the bark, stems, roots, and leaves of trees and plants. The most noticeable signs of damage include galling of the bark and branches, as well as curling of the leaves.
You can view the entire identification table created by the University of California Agriculture and Natural Resources.
Damage Inflicted
The reason you want to get rid of both whiteflies and woolly aphids is that their feeding habits harm your plants. Whiteflies and woolly aphids extract sap from the phloem by puncturing the leaves with their needle-like mouths. The phloem is the living tissue in plants that transports sucrose to the rest of the plant. Damage to the phloem can cause your plant’s leaves to yellow, appear dry, or snap off.
Whiteflies and woolly aphids also exude a sweet liquid known as “honeydew.” That sticky substance can gum up your leaves and attract ants, potentially scaring away your bugs’ natural predators.
Honeydew also produces a fungal illness called sooty mould, which only thrives on honeydew. Though sooty mould may not cause direct damage to your plant, it might expand to the point where it inhibits sunlight from reaching the leaves. This can reduce your fruit tree’s productivity or make your blossoms appear disturbed. This is especially difficult when you’re attempting to grow a beautiful garden.
Woolly aphids have the potential to spread powdery mildew from one host plant to another. Powdery mildew is a plant disease that, if left untreated, can cause stunted growth and withering plants.
Prevention
Of course, the best way to manage these white gnats is to keep them from infesting in the first place. Reflective mulches can assist with this. Reflective mulches work by reflecting UV light, which disrupts an insect’s ability to locate a host plant. Thus, it has the potential to avoid or at least delay plant infestations.
In other cases, creating a favourable habitat for natural enemies will aid in pest management. Lacewings, big-eyed bugs, minute pirate bugs, and no one’s personal favourite, the Asian multicoloured lady beetle, are all predators of the whitefly.
There is some overlap among the enemies of the woolly aphid. Lacewings, hoverflies, and ladybirds all consume woolly aphids, reducing their numbers. Tolerating some of these predators will eliminate both whiteflies and woolly aphids.
How to Get Rid of Whitefly
If you find an infestation, carefully remove the leaves containing eggs or nymphs. Alternatively, thoroughly spray down the leaves to remove any eggs or nymphs that may be present. Yellow sticky traps can also be used to control high levels of whiteflies. Insecticidal soaps and oils are another option for reducing populations. Neem oil is a viable option because it is a natural pesticide that is safe for pets and wildlife.
If you notice any plants with a high, consistent number of whiteflies, you should eliminate them. You can also use a systemic pesticide. A systemic insecticide is absorbed and transmitted throughout the plant, killing any insects that feed on it. However, this can upset beneficial insects and pollinators.
How to get rid of woolly aphids
If you want to apply natural solutions to your woolly aphid problem, start by spraying your plants with a forceful stream of water. This will help to dislodge any eggs deposited beneath the leaves and nymphs clinging to the plant. Rinsing on a regular basis will help keep the population down.
Neem oil is another an excellent option, as are a range of natural insecticidal soaps. The majority of natural soaps are created from a combination of pure soap (no dishwashing soaps with degreasers or bleach) and oil (vegetable, peanut, corn, soybean, etc.). These soaps are favoured since they are both animal and environmentally friendly, as well as effective at eradicating small, soft-bodied insects such as aphids.
If your plants are heavily infested with woolly aphids, consider trimming and eliminating infected branches. Strong insecticides are rarely required, but if the plant or tree is stressed, they can be used.