Identifying and Treating Common Azalea Pests – Your Guide to Healthier Shrubs

Do azaleas need pest control? Azaleas aren't quite as prone to damage from animal pests as some of their close relatives, but sucking insects and larvae love them. In fact some insects are so common that they're named after the Rhododendron genus, which azaleas are a part of. You'll notice a few below.

Spring is the best time to start azalea pest control. It's the easiest time to spot them, before the plant has leafed out. It's also the best time to minimize damage, removing the problem before any leaves or flowers can get hurt.

Vigilance and early detection are vital parts of azalea care, and are key to preventing the damage from these insect pests. Let's take a look at the most common azalea pests, and how to deal with each one.

Azalea Bark Scale

There are several varieties of scale that will attack azaleas, but azalea bark scale is the most common. The females latch onto stems and are covered in a waxy, cream colored egg sac. The offspring feed on the sap in crotches and forks of the plant. Their sucking behavior can damage the overall health of the plant, resulting leaf die back and discoloration.

Scale can also be identified by the honeydew they excrete, which makes leaves and stems shiny and sticky. Honeydew can also lead to the appearance of black sooty mold.

How to Treat Azalea Bark Scale

Azalea bark scale produce one new generation every year, with nymphs overwintering on the plant. Apply dormant oil in late to early spring to target the nymphs before they emerge. If you've already missed that window, apply Neem oil in late spring or early summer to target the insects in their young phase.

Azalea Caterpillar

Azalea caterpillars (Datana major) are one of those pests so commonly seen on azaleas that they share a name. They're also sometimes known as red headed azalea caterpillars, due to their flame colored heads.

They can reach over 2 inches ( 5 cm) long, and have a black body dotted with yellow spots. They feed on foliage, which can become decimated with large populations of the pest. The majority of the damage occurs summer through fall.

How to Treat Azalea Caterpillar

If you notice chewed leaves, hand pick the pests off the plant. You might also spray with Bacillus thuringiensis, a natural product that targets caterpillars. There's a link to buy it just below.

Rhododendron Borer

The rhododendron borer (Synanthedon rhododendri) is the offspring of a moth that looks similar to a hornet. The caterpillars are small with white bodies and dark heads.

The larvae burrow into the woody stems of the azalea where it overwinters. This burrowing leaves behind frass, and can even make the stems crack. their presence can also cause wilted leaves, stunted growth, and branch death.

How to Treat Rhododendron Borer

There is no chemical control for rhododendron borers. You can remove them manually by cutting away wilted and dying branches, making sure to cut well into the healthy stems. Beneficial nematodes like this on Amazon can also be helpful.

Azalea Lace Bug

If you see bugs on azalea that have fine, lacy wings and brown and black markings, you may be getting a visit from azalea lace bugs. Damage is caused by both the adults and their nymphs, which are black and spiny, as they suck sap from under the leaves. The leaves become stippled, then turn white, and finally dry and fall off the plant. In heavy infestations the defoliation can severely harm plant health.

How to Treat Azalea Lace Bug

This is an introduced pest from Japan. Treatment for adults is not effective, but nymphs may be targeted in late spring. Horticultural oil has some control but it must cover the undersides of the leaves where the insects hide.

Azalea Leafminer

Leafminers are frequent azalea insect pests. The adult is a tiny yellow moth, but its larvae are the ones to look out for. These larvae live inside the leaf and show up as black bumps near the veins. Damage begins in May and as the larva matures, it releases silk that will cause the leaf to curl. The larva overwinters in the leaf as a pupa. With excess feeding, the leaf will yellow and fall. Large infestations can cause serious leaf damage.

How to Treat Azalea Leafminer

In the fall, rake up any damaged leaves and dispose of them to remove the pupa that would become the next year’s pests. Remove leaves that have become rolled from the plant.

Black Vine Weevil

Chances are pretty good that you've seen their characteristic damage. The edges of the leaves look like someone cut them with pinking shears. The weevils are small, black, and have dots on their backs. All adults are female, and each is capable of laying up to 500 eggs.

The adults feed at night and cause the notched leaves. The larvae are white, legless grubs about 1 inch ( 2.5 cm) long. The adult’s damage is mostly cosmetic, but the larva feeds on the roots of the plant. The foliage will become yellow and overall growth is stunted.

How to Treat Black Vine Weevil

At night, go out with a flashlight and hand harvest the adult weevils. Beneficial nematodes and systemic drenches are fairly effective on the larva. Apply nematodes in mid May and again in August.

Rhododendron Gall Midge

This azalea pest can be difficult to spot. The adult is a tiny fly that lays eggs in new leaves. The offspring are maggots that feed on the tender new leaf material. After seven days of feeding, the maggots drop off and cocoon where they pupate. Gall midges can produce up to three generations annually. The feeding of the maggots causes the leaf to roll up. Damage is most evident in May and July.

How to Treat Rhododendron Gall Midge

Pluck off any damaged and curl leaves as they occur.

Rhododendron Whiteflies

Whiteflies attack many species of plant in the garden. The adults are small moth-like insects with powdery white bodies. If you shake an infected plant’s stem, a profusion of adults will fly away. Their nymphs hatch on the underside of the leaves and feed on the foliage. The leaves will become mottled and yellow. The nymphs excrete honeydew which creates sooty mold.

How to Treat Rhododendron Whiteflies

Spray the undersides of the leaves with horticultural oil or soap.

Frequently Asked Questions