Order: Hemiptera (TrueBugs)Family: Psyllidae, TriozidaeCommon Names: Plant Lice, Jumping Plant Lice, Lerps, Lerp Psyllid, Gall Psyllid, Lilly Pilly Psyllid
Psyllids are tiny sap-sucking insects that feed on the nutrient rich liquids inside leaves and transport tissues (xylem & phloem). Most species of psyllid will only feed on one specific host plant, however some species are known to broaden their preferences to plant varieties within the same family.
How to Get Rid of Lerps on Austrian Pine Trees: A Complete Guide
As a gardener and arborist, I often get questions from clients about pest problems on their trees. One common issue I see is infestations of lerps on Austrian pine trees. If left untreated, lerps can cause significant damage, so controlling these pests is important for protecting the health and beauty of pine trees. In this comprehensive guide, I’ll explain what lerps are, the signs of infestation, and effective organic and chemical treatment methods for getting rid of lerps on Austrian pines.
What Are Lerps?
Lerps are small sap-sucking insects that belong to the psyllid family. They produce a protective covering over themselves made of wax and honeydew secretions. This covering resembles a bump or scale on pine needles and branches. Lerps feed on the sap from pine trees, extracting vital nutrients and fluids. Heavy infestations can cause yellowing or browning of foliage, stunting of new growth and branch dieback. The honeydew secretions left behind also promote sooty mold growth.
Identifying Lerp Infestations
It’s important to regularly inspect pine trees to catch lerp infestations early before major damage occurs. Some signs to look for include:
- Clusters of small bumps or scales on needles and branches
- A sticky, syrupy substance (honeydew) coating needles
- Sooty black mold on needles or branches
- Yellowing, browning, or wilting of foliage
- Stunted shoot growth
If you spot these symptoms, take a closer look at the branches and needles to confirm the presence of lerps. Their waxy outer coatings are quite distinctive and easy to identify. Also, look for ants, wasps, and bees that are often attracted to the sugary honeydew secretions.
Organic Lerp Control Methods
For mild lerp infestations, these organic approaches can be effective:
Pruning – Remove heavily infested branches and dispose of them away from the garden to reduce lerp populations.
Horticultural oils – Coating branches with lightweight summer oils can smother lerps and disrupt their protective coatings.
Insecticidal soaps – Target lerps with insecticidal soap sprays. Apply thoroughly to coat all infested areas.
Natural predators – Attract beneficial insects like ladybugs, lacewings, and parasitic wasps that prey on lerps.
Neem oil – The azadirachtin in neem oil helps disrupt lerp growth and reproduction.
High-pressure water sprays – Knock off clusters of lerps with a strong stream of water.
For best results, rotate between several of these organic options and repeat applications on a 7-14 day schedule. This keeps lerp populations from rebounding.
Chemical Treatments for Severe Lerp Infestations
If organic methods aren’t providing adequate control, chemical insecticides are stronger options for knocking back heavy lerp populations:
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Systemic insecticides (like acephate or imidacloprid) – Applied as drenches or injections to travel through the pine’s vascular system. Offers 1-2 months of control.
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Contact insecticides (like bifenthrin, carbaryl) – Sprays that coat needles and branches to kill lerps on contact. Shorter residual of 5-7 days.
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Insect growth regulators (like pyriproxyfen) – Disrupt the growth and molting of juvenile lerps.
When using any chemical pesticide, carefully follow label application guidelines. Avoid applying them during hot weather or when trees are stressed. And be mindful of protecting pollinators by spraying early mornings or evenings when bees are less active.
Preventative Lerp Management
Along with control methods, preventative maintenance is key to managing lerps over the long-term:
- Monitor trees weekly for early detection
- Remove and destroy heavily infested branches
- Avoid over-fertilizing, which stimulates growth that attracts lerps
- Promote air circulation and sunlight penetration with proper pruning
- Keep trees healthy with proper watering and mulching
What are the signs that you have Psyllids
We have 100s of species of psyllids in Australia. The most common species are the Lilly Pilly Psyllid, Lerp forming Psyllid, Gall forming Psyllid and Free Living Psyllid. These are all mostly found on our native plants and are most noticeable during the nymph stages.
These psyllids are often visible on the new growth of the plant. After they hatch, the nymph crawls into position on a young leaf to begin feeding and molting. After the first molt a pock mark or small pit appears on the leaf. As it grows and continues to molt, this pit becomes bigger, looking like a pimple on the leaf of the plant. The adult emerges after the final molt and the whole cycle begins again! Waterhousia floribunda is a particularly juicy variety to the Lilly Pilly Psyllid and often gets attacked.
Damage
Cosmetic damage to the leaves, causing the leaves to curl and pimple. Severe infestation can cause some leaf drop and stunt growth but it is rare that it will kill the plant.
Often seen on natives such as Eucalyptus, the nymphs will burrow into the leaf, causing a gall to form around it as protection. Once the nymph has reached maturity, it breaks out of the gall as an adult.
Damage
Only cosmetic, overall never getting so bad as to kill the tree.
These psyllids excrete a white, sugary substance to cover themselves as protection whilst they feed on the leaf of the plant. This is called a lerp. The lerp gets bigger as the nymph molts, finally emerging as an adult. Lerps are eaten by many animals such as birds, possums, flying foxes and gliders. They can even be eaten by humans as a sweet treat!
Damage
Light infestations cause a mottled appearance on the leaves, whereas a severe infestation can cause the tree to defoliate, affecting its growth and appearance. In some cases it can cause the tree to die.
Free-living psyllids are just that, free living! They feed on the new growth of the plant and create no protective cover like the previous psyllid types. Both the adult and nymphs are seen on the plant at the same time. They tend to target a lot of natives such as grevillea, wattles and eucalypts as well as ornamental plants such as Smoke Bush.
Damage
Can produce Sooty Mold and other waxy secretions, often deforming new growth with bad infestations.
What do Psyllids look like?
Psyllids have 3 life-cycle stages: egg, nymph and adult. Most species will go through 3 to 5 generations per year.
Adults look like a tiny, winged insect approximately 2-3mm in length, the wings pointing back over the abdomen in a V shape.
Nymphs are usually a miniature version of the adult form but without wings, more scaly and can look flattish. Some species hide under what is a called a ‘Lerp’, which is a little white, sugary covering that shields the nymph whilst it feeds and molts. Others cause pits or galls in the leaves.
Eggs are found singly or in clusters, sometimes found upon the leaf and its edges, other species insert the eggs into the leaf tissue.
How to Save Your Diseased Pine Trees
FAQ
How to get rid of LERP?
What is the problem with the Austrian pine tree?
How to get rid of psyllids naturally?
What is killing my Austrian pine trees?
How do you treat Diplodia tip blight on Austrian pine trees?
The Austrian pine (Pinus nigra) is a hardy, low-maintenance evergreen tree that’s often planted as windbreaks and border rows. Treat your Austrian pine trees for the common fungal disease Diplodia tip blight by pruning away the diseased or cankered branches. Spray the pine trees with a fungicide according to the directions on the label.
How do you get rid of pine needles in the winter?
Spray your pines with a dormant horticultural oil in late winter to kill the over-wintering scale insects. Dothistroma needle blight is another fungal disease that attacks Austrian pine trees, causing the needles to brown and develop reddish-brown spots or bands.
How do you repot a pine tree?
Pine trees generally grow well with confined roots, so repotting won’t be a frequent task. When the tree finally does become root-bound, the best repotting strategy is to carefully remove it from the pot, trim back about one-third of its root mass, then repot in the same container using fresh potting mix.
How do you care for a pine tree?
Inspect the tree for any dead or damaged branches. Use a sharp pair of pruning shears to cut the branches back to the main trunk. Prune the tree in a way that maintains its natural shape. Dispose of the branches by chipping them or composting them. Pine trees are evergreens, which means they produce new growth throughout the year.