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How to Get Rid of Oak Processionary Moth

How to Get Rid of Oak Processionary Moth

There’s a new pest on the block, increasing in numbers, defoliating trees and posing a serious threat to human health.

The larvae (caterpillars) of the Oak Processionary Moth (Thaumetopoea processionea) or OPM predominantly feed on oak tree leaves, but also hornbeam, hazel, beech, chestnut and birch.

Oak processionary moth life cycle

Oak Processionary Moth Rash

Although the leaf damage can be severe, OPM caterpillars pose a serious risk to human health. The caterpillars are covered in bristle-like hairs containing a chemical toxin. Human contact with the hairs can provoke allergic reactions manifested as skin rashes, conjunctivitis and respiratory problems such as pharyngitis and asthma. Health problems can occur even if the larvae are not handled as the hairs break off readily and are dispersed in air currents.

Abandoned caterpillar nests contain shed caterpillar skins, pupal cases and vast numbers of detached hairs and should be treated with extreme caution.

Eggs are laid in august and they hatch into caterpillars between April to July feeding on the leaves and at their most dangerous. They are small and coloured black with a white underside and long white hairs all down their body.

The likelihood of human contact is increased as Oak Processionary caterpillars are most abundant on urban trees, along forest edges and in amenity woodlands

Moth populations are well established and increasing in northern Europe due to climate change. Oak Processionary Moth is established in London and has been detected as far north as Sheffield.

Oak Processionary Moth Treatment 

The biological insecticides Dipel DF & Bruco contain insecticidal bacterial agents derived from a naturally occurring soil micro-organisms. These are highly effective at controlling caterpillars. Dipel DF is approved for use in 190 different crop types including vegetables, fruit, forestry, and amenity situations.

Apply Dipel DF or Bruco to the caterpillar stage between April and end of May for best results. It is non-toxic, biodegradable and safe to other insects, fish, animals and humans and permissible in organic situations. Once a caterpillar has ingested Dipel DF or Bruco it stops feeding in minutes and kills OPM caterpillars within 24-72 hours.

For a spraying latter stages of caterpillar growth try a Deltamethrin based insecticide such as Decis Protech. For ultimate control, these Bruco or Dipel DF can be tank mixed with Decis Protech.

It is worth promoting regrowth and recovery of trees and shrubs which have been damaged by OPM.  This can be encouraged in a number of ways.  Tank Mixing a liquid seaweed product with the chosen insecticide will have this effect on the foliage of the plants.  A suitable product would be Amvista L9 Liquid Organic Seaweed or Maxicrop Seaweed Extract.

A further method would be to apply a slow release fertiliser to the soil in which the trees or shrubs are growing.  Two suitable products would be Bonemeal or Arbor Gold

Frequently Asked Questions

Are Oak Processionary Moths dangerous to humans?

The caterpillars of the Oak Processionary Moth are covered in hairs which contain a protein called thaumetopoein. This protein can cause an allergic reaction on human skin. Alongside this there are various other health risks related to these caterpillars such as skin inflammation (hives, dermatitis), eye or respiratory tract irritation, dizziness and fevers.

What should I do if I get a rash from an Oak Processionary Moth?

In the majority of cases the rash will calm down and disappear after a couple of days. If however, the rash makes you begin to feel unwell you should see your doctor as soon as possible. They will prescribe you with either an anti-histamine or in some cases a steroid cream to calm down the allergic reaction.

What can I do to avoid getting irritations from Oak Processionary Moth caterpillars while treating the area?

When treating the area for Oak Processionary Moth, you should wear PPE to avoid the protein filled hairs of the caterpillars which can cause you irritations on your skin. We advise wearing full coveralls, faceshield and gloves. Alternatively, take a look at our safety clothing bundle which will have everything that you will need.

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