red-necked longhorn beetle

Symptoms

A large black longhorn beetle with a bright red-orange patch on the thorax (pronotum) and very long antennae; the larvae bore long tunnels in the trunk and main branches of stone-fruit trees (peach, cherry, plum, apricot), pushing out coarse fibrous frass and sawdust from cracks at the base; branches wilt, the tree declines and can be girdled and killed.

Plants affected

• peach
• apricot
• sweet cherry
• European plum

Easily confused with

• bacterial canker of cherry

  How to tell them apart: Aromia bungii (red-necked longhorn beetle) is a wood borer: look for round-to-oval exit holes (about 6-10 mm) low on the trunk and scaffold branches, coarse fibrous reddish frass (chewed wood and sawdust) packed in bark crevices or piled at the base, and gum mixed with this frass. Adults are striking - glossy black with a bright red pronotum (neck). Damage is localised to galleries inside the wood and whole branches flag suddenly in summer above the tunnelled section. Pseudomonas syringae pv. morsprunorum (bacterial canker) is a pathogen: look for sunken, dark, flattened cankers on branches and trunk, often with a clear amber gum oozing from the canker margin (gum WITHOUT any sawdust or frass), and in spring 'shot-hole' leaf spots plus blossom and spur blight. Cankers expand most in cool wet autumn/spring weather and there are no exit holes or fibrous frass.

• honey fungus (Armillaria root rot)

  How to tell them apart: Aromia bungii (red-necked longhorn beetle) reveals itself by piles of fibrous, sawdust-like frass and coarse wood shavings pushed out of bark cracks low on the trunk and main scaffold limbs, with oval-to-round exit holes (about 6-10 mm) and adults that are glossy black with a bright orange-red 'collar' (pronotum). Damage is borer tunnelling under the bark, so wilting branches dry out while the wood beneath shows galleries packed with frass. Armillaria mellea (honey fungus) instead shows creamy-white, fan-shaped mycelial sheets between bark and wood at the root collar, black bootlace-like rhizomorphs in the soil and on roots, and honey-coloured toadstools clustered at the tree base in autumn. With Armillaria the bark at the collar is sunken and rotten and there are no insect exit holes or sawdust frass. NOTE: Aromia bungii is an EU-quarantine priority pest — if you see the orange-collared beetle, oval exit holes or wood-shaving frass, report it to your National Plant Protection Organisation (NPPO) immediately.

• European brown rot / blossom blight

  How to tell them apart: Aromia bungii (red-necked longhorn beetle) is a wood-boring quarantine beetle: look on the TRUNK and large scaffold branches for round-to-oval exit holes (~6-10 mm), heaps of coarse pale sawdust-like frass at the base and in bark crevices, and gum oozing directly from the bore galleries on thick old wood. Monilinia laxa (brown rot blossom blight) is a fungus: it kills BLOSSOMS and young twigs, leaving sunken twig cankers with amber gum at the canker edge and tufts of grey-brown powdery spores on blighted flowers and shoots after wet, cool spring weather. Decisive sign: visible bore holes plus dry frass means the beetle; grey fungal sporulation on dead blossoms and small twigs with no holes means brown rot. Aromia bungii is an EU quarantine organism (Reg. 2019/2072 Annex II) — if you see exit holes and frass, report it immediately to your national plant protection organisation (NPPO) and do not move or burn the wood yourself.

Common questions

How do I recognise red-necked longhorn beetle on peach?

A large black longhorn beetle with a bright red-orange patch on the thorax (pronotum) and very long antennae; the larvae bore long tunnels in the trunk and main branches of stone-fruit trees (peach, cherry, plum, apricot), pushing out coarse fibrous frass and sawdust from cracks at the base; branches wilt, the tree declines and can be girdled and killed.

Do I have to report red-necked longhorn beetle?

Yes. red-necked longhorn beetle is a regulated quarantine organism in the EU. A suspected finding must be reported to your national plant protection organisation — they will confirm it and tell you what to do next.

How is red-necked longhorn beetle treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.