Whiteflies are one of the worst pests you can have since they can quickly infest your plants both indoors and outdoors. They cause damage by sucking the juices from them. Whiteflies can also infect your plants with disease and cause a sooty mold to grow on the plant foliage, giving leaves an abnormal black color. When infestations are too large you will see masses of tiny white insects crawling. They will fly when disturbed, unlike mealybugs which look similar.
It is also possible for you to see more ants in the garden since they feed on the honeydew produced by whiteflies. Because ants feed on what whiteflies produce, they may even protect them from predators. Leaves will feel sticky from the honeydew substance.
Synthetic pesticides are not very effective in controlling these pests since they can develop resistance. These chemicals are harmful and will end up killing beneficial insects and pollinators. So it is better to use organic methods which are detailed below.
What are Whiteflies?
Whiteflies are tiny insects that can be as small as 1 or 2 millimeters with wings that span with a width of around 3 millimeters. They have oval bodies that when looked closely look like they are heart shaped, similar to white moths. They are related to aphids and belong to the insect suborder Sternorrhyncha and are part of the Aleyrodidae family. There are between 1,200 to 1,500 species of whiteflies which are not truly flies. Greenhouse whitefly (Trialeurodes vaporariorum) is a common indoor species.
You will find these little bugs living in the bottom of leaves, especially around the veins. It can be hard to spot whiteflies as they love hiding in plant foliage, but their white color betrays them. So make sure to check under your leaves and especially around the new growth, since they prefer tender leaves. After they drain a leaf, they will move to the next.
How do Whiteflies Reproduce?
These are warm weather insects that will reproduce all year round. Since whiteflies will not survive the cold weather, those who live in cold climates (USDA zones 7 and colder) will only see them during the summertime. They are a problem in greenhouses and for household plants, since they can spread quickly in closed environments. Make sure to keep your plants healthy so they can ward off pests and diseases.
Adults lay eggs on the bottom of leaves, which may go unnoticed until you have a huge infestation. Eggs turn into larvae and then grow into adults. This cycle takes between two weeks to a month depending on the whitefly species. Since they have short cycles, they can increase their population sizes very quickly.
Female whitefly adults can lay up to 400 eggs during their lifetime which varies between one to two months depending on the species. These eggs are pale yellow and are placed on the bottom of the plant’s top leaves. Eggs can take between five to twelve days to hatch. These nymphs, which are called crawlers, look like small mealybugs and have no wings. As soon as they hatch they begin sucking on the plant’s sap. At first they will move a lot, then tend to stay in one spot towards the end of the nymph period. They will not eat during the pupal state, and they turn to young adults in less than a week.
Whitefly Plant Damage
Having these insects will weaken the growth of your plant since they feed on its juices. Leaves can turn yellow and shrivel, until they fall off. Huge infestations can kill your plants. They can fly and spread to other healthy plants, spreading disease through their mouths. So it is important to separate any infected plant and try to control the problem as soon as possible. Also check and quarantine new plants brought from nurseries before introducing them into your garden or home.
The sooty mold they cause doesn’t harm the plant, but it may stress it from insufficient photosynthesis if too many leaves are affected.
Whiteflies love my hibiscus flowers which are exotic hybrids I got in Boquete. They cover the stems and leaves, while stunting the growth of my gorgeous flowers. Hibiscus are one of their favorite plants, as well as other flowers such as poinsettia, petunia, begonia and fuchsia. Susceptible vegetable crops include tomatoes, grapes, cucumbers, potatoes, citrus, squash, okra, peppers, and eggplants.
How to Control Whiteflies
The most efficient way to control outdoor whitefly infestations is to introduce beneficial insects since they will do the job for you. These predators can destroy whiteflies at all stages of their lives. Green lacewing (Chrysoperla carnea) and female beetles can eliminate the larvae, while tiny parasitic wasps (Encarsia formosa) lay eggs in their bodies. These wasps are not harmful to humans and they are very effective at greenhouse control.
Several species of ladybugs are also useful at controlling these pests, as well as aphids and scale insects. Predatory mites, dragonflies, damselflies, and hummingbirds will also help you. Spiders will net the grown insects for food. Predators and parasites are not for indoor house plants. You can plant some species that will naturally attract them or buy them from sellers.
Some plant species repel whiteflies, so if you have this problem you can make specific additions to your garden. Marigolds are quite useful at repelling tomato whiteflies because they contain limonene. This chemical repels and slows them down. Researchers suggest adding marigolds to your tomato plots.
Spray Them Off
Spraying whiteflies with a garden hose will get rid of these insect pests naturally, as it also dislodges eggs and nymphs. Adults will be scattered. Spraying can also remove the sooty mold from the infected leaves. The downside to using this system is that you will have to do this daily for quite some time, as females will continue laying eggs. To eliminate them for good you need to disrupt their life cycle, so no more bugs hatch. Be sure to pay attention to the underside of leaves where the larvae and eggs reside.
Mix two tablespoons of organic dishwasher soap or liquid soap (so it doesn’t harm your plants) with one gallon of water and mix well. You can also do a garlic spray or use insecticidal soaps. Place this solution in a spray bottle and spray the underside of leaves every two or three days until the problem is solved. The spray will knock off the small bugs and kill adults and eggs. It is best to do so early in the morning or late in the afternoon so the soap does not burn your plants.
Use neem oil in the morning or in the evenings just like the soapy water. There are natural neem pesticides that you can buy or you can mix 1 oz (30 ml) of neem oil in one gallon of water. Place this mixture in a spray bottle and cover your plant with it, paying special attention to the undersides of leaves. Just like soapy water, you will have to do this every couple of days to stop the cycle and kill adults. Neem oil and other horticultural oils are more expensive alternatives than soapy water.
Surprisingly a handheld vacuum cleaner can eliminate these pests from your plants. Start doing so as soon as you notice these little tiny white bugs under the leaves. This method is best for household plants, as it has limited effectiveness since it only kills adults. Make sure to discard them properly, so the insects don’t escape. Place the vacuum bag in the freezer for 24 hours to kill these insects that don’t like the cold, then empty the bag in the trash.
Sticky Yellow Traps
Sticky yellow traps are an effective and low cost method of controlling adult and immature whiteflies according to the Journal of Insect Science. Adults are attracted to the yellow color and become attached to the glue-like substance. Place them near your garden or greenhouse plants to reduce the population number. This method is not effective for larvae, so it should be combined with other methods. You can also control pests such as thrips, fruit flies, leaf miners, fungus gnats, and aphids with this method.
Aluminum Reflective Mulch
This mulch makes it hard for these insects to find host plants since they will be blinded by the light. Use this to protect your vegetables from the diseases that these pests transmit.
Another way of controlling whitefly infestations is pruning. However this method is not very efficient and it may backfire since too much pruning can stimulate new growth which will attract more insects. Make sure to discard the foliage of plants correctly, by burning them or placing them in the trash. Infected plant parts should never be composted.
Control Nitrogen Levels
Make sure that your soil content isn’t too high in nitrogen, which creates an environment that is conducive to these bugs and other pests. Some fertilizers may have very high nitrogen content.