Bonsai pests are one of the main obstacles that you may run into. If you have an infestation, it can be frustrating and scary, but you are not alone. We will go over some of the most common pests that may attack your bonsai trees, how to identify and get rid of them, hopefully for good!

Spider Mites

The most common pests on bonsai trees are Spider Mites. These arachnids often form groups under the leaves and eat the tissue from between the leaf membranes.

Spider Mite Identification

Tiny eight-legged spiders. They come in many different colors, but most are red, yellow, brown, green, or clear.

Red Spider Mite - Bonsai Pests — Red Spider Mite

Spider Mite’s Favorite Plants

Elms
Evergreens
Maples
Oaks

Life-Cycle of the Spider Mite

Spider Mites are arachnids, so they create webbing on the outside of the plants. The eggs are laid and attached to this web for about 72 hours, at which point they hatch. These insects have two nymph stages. In each, their size increases and they grow legs. They are dangerous to your plant at this stage, because they require more and more food before the final adult stag. Once the spider mites reach adulthood, the females become able to lay eggs. This is a critical stage, because they can lay up to 100 eggs each. It only takes a few generations to fully take over the plant.

How to Remove Spider Mites

Natural Predators

The most natural way to kill bad bugs is to introduce good bugs. Ladybugs will have a feast on spider mites. Ladybugs are considered good luck and will wipe out a spider mite infestation in no time. There are other parasitic mites that can be used in lieu of ladybugs. Purchase these from a local nursery or even online!

Organic Pesticides

Generally, organic pesticides do not do as well as toxic chemicals. If you aren’t growing food, it’s not usually necessary to strictly use organic pesticides on bonsai. If you tree is sturdy, you can try to use a stream of water to blast the spider mites and webbing away from the plant. This will likely not work for heavy infestations. It may also damage your bonsai, so we do not recommend.

You can also try to mix garlic and a hot pepper in water and spray it all over your plant. Spider mites do not appreciate this concoction and might leave.

Chemicals

The thing to keep in mind when using toxic chemicals is that it will usually kill ALL insects on the plant. There is no poison just for bad bugs.

White Flies

White flies are a common type of bonsai pests for indoor bonsai trees. Like many pests, they will often live on the underside of the leaves, sucking the sap from between the membranes. Sometimes they will secrete a sappy substance known as honeydew, which can attract ants, and create additional fungal infestations on your bonsai.

White Fly Identification

You may notice the flies buzzing around your tree. Lift your leaves and check the undersides. The white flies will fly away, but their eggs will be attached. Check for small white egg sacks that will be attached to the leaves.

White Flies are common bonsai pests — White Fly

White Flies Favorite Plants

White Flies usually prefer plants in your home. No bonsai tree is off limits to these small white flies. They may also infect bonsai trees kept under breezeways or roofs.

Life Cycle of the White Fly

Eggs are laid underneath the leaves. The eggs take about 1 week to hatch into the nymph stage. At this stage, the nymphs still have no wings, so they can only crawl. They will pierce the leaf membrane and begin eating the sap from the leaves. It takes about a month for these nymphs to molt. Molting is a process of shedding their former shell. With their shell gone, the white fly’s wings are free. This is the final stage, and the white flies will live about 6 weeks longer.

How to Remove White Flies

Fungus

The fungus beauvaria bassiania is available at any garden center, or major stores like Lowe’s and Home Depot. This fungus produces spores that break through the insect’s cuticle. This will make the insects sick and eventually die.

Insecticidal Soap

Insecticidal soap uses fatty acids as the active ingredient, rather than a toxic chemical. This type of soap will not harm your plant nor most beneficial insects like ladybugs or bees. It only works on insects without hard exoskeletons. Great for aphids, mealybugs, whiteflies, and thirps, to name a few! This is available anywhere, but you can also opt to make your own.

Aphids

Aphids are one of the most common bonsai pests. Sometimes called greenflies, aphids are soft-bodied insects that love sap. You will often read that aphids are harmless to healthy plants, but this is not always the case with bonsai. Small trees have less room and as these insects reproduce, they can soon take over your plant.

Aphid Identification

Aphids are often grouped together along the stem of the undersides of leaves. They are usually easy to spot with the naked eye, upon inspecting your plants. However, without inspection, there are few indicators that are common with an aphid infestation. Look for beetles or ants on your plants. They love to feast on aphids, so are common on aphid infested plants.

Aphid’s Favorite Plants

Aphids like trees. You will likely become very familiar with these insects as a bonsai grower. They don’t discriminate between leaves or needles. They can suck sap out of both. Virtually all bonsai trees and shrubs are susceptible to aphid infestations.

Life Cycle of the Aphid

The life cycle of Aphids is quite interesting. Stem mother’s are small females without wings. They can reproduce asexually over the summer months. They do not deposit eggs but carry them internally.

Once the plant gets too crowded, some of the aphids morph into adulthood and grow wings. Males and females then mate and the female lays eggs that last through the winter.

This cycle only happens in places with cold winters. Aphids are all over and this may not need to occur.