Bonsai Pests

What it looks like

Bonsai Symptoms

Which plants does it affect

Treatment

Ants

Small red, black or brown creatures

Do not harm the tree by themselves but carry aphids and mealy bugs.

All

Spray with nicotine or pyrethrum.
If found nesting in the bowel repot immediately, remove soil and soak roots in weak pyrethrum, then add new soil

Aphids

Grey, black or green

Secret a substance that ants like, so check to see if ants are on the bonsai as well. Weakened leaves and branches

All (particularly pines)

Alternate spraying with systemics and pyrethrum. Root aphids will have to be sprayed when the bonsai has been removed from the pot

Caterpillars

Small, long, multi-legged creatures

Trails of slime on the leaves and branches

All

Spray with pyrethrum or rotenone

Earthworms

Long, curly and pink colored

Disturbances on the top of the soil can usually be seen

All

They will usually surface when disturbed and then can be picked up and removed. Or use pyrethrum solution

Mealy bugs

White, found in patches on leaves

Growth slows. Looks like pieces of cotton on the plant. Leaves turn yellow and droop

All

Spray with a systemic insecticide solution

Red Spider mites

Size of a pinhead and on white paper held beneath the branches when shaking

Cause the bonsai to turn a grey color and then later on brown

Usually pines, juniper and cryptomeria

Use a dusting sulphur spray

Scale insects

Appear a small white, yellow  or brown lumps

Give off a sticky secretion, sometimes have waxy shells, clusters of brown or yellow can be seen. Trunk distorts, branches droop and leaves turn yellow,

Prefer ficus style plants

Spay with a lime and sulphur solution