Asian longhorned beetle surveillance: traps, host trees and the eradication clock

Anoplophora glabripennis is a quarantine pest in North America and Europe for a reason: a female lays eggs in the bark of a living host, the larva tunnels into the wood, and by the time exit holes appear the tree has been infested for at least a season. Every eradication programme that has worked has worked by finding the beetle early.

The chemistry

The ALB signal is a male-produced aggregation pheromone built from an ether and its aldehyde precursor — 4-(n-heptyloxy)butan-1-ol and 4-heptyloxy-butyraldehyde. Both components matter; a single-component lure catches a fraction of what the pair does, and the ratio between them is part of the specification.

Citrus longhorned beetle, Anoplophora chinensis, responds to the same pair. That is convenient for a port programme screening both species and inconvenient for a programme that needs to know which one it has: the trap does not separate them, so every detection still goes to an identifier.

Host trees, not trap grids

ALB surveillance is organised around host trees rather than around hectares. Maples dominate the preferred list, with willow, elm, horsechestnut, poplar and birch close behind. A trap in a conifer plantation catches nothing regardless of how well it is hung.

• Place traps in the canopy of known hosts, 8–12 m up, on the sunny side.
• Prefer trees with a history of use — street trees, port precincts, importers’ yards, nurseries.
• Cluster traps where host density is highest, not evenly across a grid.
• Record the host species per trap; it is the covariate that explains most of the variation.

The season and the clock

Adult emergence runs from late spring into summer, with a peak that varies by climate and by whether the population is established indoors or outdoors. Traps go up before emergence and stay up through the flight, checked weekly. Because adults are weak fliers and stay near the host, a single trap can be colonised for weeks — which makes trap servicing as important as trap placement.

The eradication clock matters here: delimitation surveys need to find the boundary of the infestation within one or two flight seasons, and each season of delay multiplies the area that later has to be treated. That is why ALB programmes buy sensitivity, not coverage — more traps in the right host trees beats a sparse grid over a wide area.

Documentation for a regulatory programme

Programmes run by a plant protection organisation need lot traceability: which lure, from which lot, deployed where, on what date. Certificates of analysis, GC traces and SDS are supplied per lot, and retained samples are kept so a detection can be tied to the material in the trap.

If the programme has to justify its trapping design to an auditor, the reasoning in this page — host-driven placement, canopy height, weekly servicing — is the part that usually needs writing down.

Compounds used in this programme

The materials below cover the blend this programme is usually built from. Where a specification names a different ratio, the components are the same — the ratio is what we quote against.

Assay and isomeric composition are stated per lot. Packing starts at 1kg / 25kg / 100kg with development quantities below that.

Questions this programme usually raises

Do the two Anoplophora species need different lures?

No — the same two components attract both. They cannot be separated by trap catch, so species confirmation still requires a specimen.

Why canopy height instead of 1.5 m?

ALB adults move through the crown and mate on branches. Traps at ground level catch a small fraction of what canopy-height traps catch in the same host tree.

How many traps does a delimitation survey need?

It is set by host tree density within the survey area, not by area alone. A dense street-tree precinct needs many more traps per square kilometre than an industrial yard with scattered hosts.