Ants & Scale Insects on Fig Trees: Treatment & Prevention

Quick Answer

Ants and scale insects work as a team on fig trees. Scale pierce the bark to drink sap and excrete sticky honeydew, and ants farm that honeydew, protecting the scale colonies from predators. The signs are trails of ants on the trunk, small waxy bumps on bark and stems, sticky leaves, and a black sooty mould coating. Break the cycle by excluding ants with a trunk barrier, scrubbing and pruning off scale, and applying horticultural oil. Once ants are gone, natural predators usually finish the job.

This is really two pests in a partnership, which is why treating one without the other rarely works. Understand the relationship and the solution becomes obvious: cut the ants out of the equation and the whole system falls apart.

What to Look For

The clues stack up together: trails of ants running up and down the trunk, small dome-shaped or waxy bumps fixed to bark or stems (the scale insects themselves), sticky honeydew residue on the leaves, and a black sooty mould coating leaves or the surfaces below the tree. Seeing ants marching purposefully up a fig is your cue to look closer for the scale they are almost certainly tending.

How the Partnership Works

Scale insects settle on bark and stems, insert their mouthparts, and feed on the tree's sap. They excrete the excess sugar as honeydew. Ants prize that honeydew and will actively defend the scale colonies from ladybirds, lacewings, and parasitic wasps that would otherwise eat them, essentially farming the scale like livestock. The sooty mould is a secondary fungus that grows harmlessly on the honeydew but blocks light and looks awful.

Is It Serious?

A light infestation is more unsightly than dangerous, but a heavy, ant-protected scale colony saps real vigour, and the sooty mould reduces the leaf's ability to photosynthesise. Left alone with ants standing guard, populations can build year over year. The encouraging part is that these pests have many natural enemies, so removing the ants' protection tips the balance back in your favour quickly.

My Treatment Plan

Exclude the ants first. Wrap a tape collar around the trunk and coat it with horticultural sticky glue (never apply glue directly to bark). This is the linchpin.
Prune out heavily infested branches and bin the material.
Scrub armoured scale off the bark with a soft brush and soapy water.
Apply horticultural oil to smother the mobile crawler stage in early summer.
Let predators finish the job. Once ants are excluded, ladybirds and parasitic wasps usually suppress the remaining scale within a single season.

⚠️ Never glue the bark

Apply sticky ant barriers to a collar of tape or fabric wrapped around the trunk, never directly onto the bark itself. Horticultural glue on bark can damage the tree and trap beneficial insects you want to keep.

Preventing It Next Season

Keep an ant barrier in place through the growing season on trees with a history of scale, and inspect bark and stems periodically for the first waxy bumps so you can act early. Preserve the beneficial insect population by avoiding broad-spectrum sprays, and keep trees healthy and unstressed, since vigorous trees shrug off light scale pressure. For potted trees, standing the pot in a shallow water tray creates a simple ant moat.

Not sure it’s scale? Sticky leaves and sooty mould also come from aphids and black fly. Check your tree’s symptoms against all 18 conditions with the free interactive tool.

Run the Symptom Checker

Frequently Asked Questions

Why are there ants all over my fig tree?

Ants running up and down the trunk are almost always farming sap-sucking insects like scale or aphids. Those pests excrete sugary honeydew, and the ants harvest it, protecting the colony from predators in exchange. The ants are not eating your tree directly, but their presence is a reliable sign that scale or aphids are feeding on it.

What is the sticky stuff and black coating on my fig leaves?

The sticky residue is honeydew, the sugary waste excreted by scale insects and aphids as they feed on sap. The black coating is sooty mould, a harmless-but-ugly fungus that grows on the honeydew. Both clear up once you control the insects producing the honeydew and exclude the ants that protect them.

How do I get rid of scale on a fig tree?

Scrub armoured scale off the bark with a soft brush and soapy water, prune out heavily infested branches, and apply horticultural oil to smother the mobile crawler stage in early summer. Just as important, exclude the ants with a barrier, because once ants can no longer protect the scale, natural predators usually clean up the rest within a season.

How do I keep ants off my fig tree?

Wrap a tape or fabric collar around the trunk and coat it with a horticultural sticky barrier, never applying the glue directly to the bark. This physically stops ants from climbing up to tend their scale colonies. For potted trees, standing the pot in a shallow tray of water also creates a moat ants will not cross.

Do I need to treat the scale if I just get rid of the ants?

Often the ants are the key. Ants actively defend scale and aphids from ladybirds, lacewings, and parasitic wasps. Remove the ants and those natural predators typically bring the scale under control on their own within one season. In heavy infestations, combine ant exclusion with oil sprays and manual removal for faster results.