Hornet moth in poplar and willow plantations

Sesia apiformis is a clearwing that spends most of its life as a larva inside the lower trunk of poplar and willow, often below ground level. Adults emerge in early summer, live a few days and mimic hornets closely enough that they are usually recorded as wasps, if they are recorded at all. For a short-rotation plantation, the practical consequence is that symptoms appear two to three years after establishment.

Where the moth actually is

Attacks concentrate at the butt of the tree, at or just below the soil line, and around wounds — mechanical damage, animal browsing, harvest scars. Traps hung at 0.5–1.5 m on the trunk of susceptible trees catch males as they search the butt for emerging females, which is the only stage at which the population is mobile enough to be sampled.

• Hang traps low — trunk height, on the shady side in hot climates to slow lure degradation.
• Focus on plantation edges and on blocks with a history of damage or wounding.
• Include the headland trees; they take more damage than the interior in most plantations.
• Keep trap positions fixed across the rotation, so a series builds up.

Single generation, narrow window

There is one flight per year, lasting three to five weeks in June and early July across most of the range. Because there is no second chance, the deployment date is the whole programme: traps up by early June, checked weekly, removed when catch has been zero for two consecutive checks.

Coppice and short-rotation blocks are cut on a cycle that is often shorter than the time it takes for symptoms to appear. That makes trap data the only early signal a grower has, and it makes a missed season expensive.

Blend and dispenser

The hornet moth blend is built on a C18 dienol with a specific double-bond geometry; the related (Z,Z) isomer is the sequoia pitch moth signal, and substituting one for the other produces a trap that catches the wrong insect confidently. We quote the geometry explicitly and state it on the certificate.

Dispensers should be fresh each season. A lure that has been open in a warm store releases poorly, and a low catch will then be read as a low population.

What a programme does with the data

Hornet moth management is largely about establishment risk: which blocks are being attacked, and whether the attack is spreading along a row. Trap catch, read against the block map, shows the direction of spread. For a grower deciding where to plant the next cycle, that is more useful than a damage estimate.

Documentation

Per-lot certificate of analysis, GC trace, SDS and packing list. For plantation schemes with certification requirements, the lot documentation is what ties a monitoring record to the material used.

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

Is the hornet moth lure the same as the pitch moth lure?

No. They share a chemical family but differ in double-bond geometry, and the two are not interchangeable. Order by species, not by "clearwing".

Why do I only find damage and never moths?

Because the adult stage lasts days and the larva lasts years. A pheromone trap is the only practical way to detect the adult flight; visual surveys find old damage.

Do traps need to be at ground level?

Low trunk height, 0.5–1.5 m, works best — the moths search the butt of the tree. Traps high in the canopy under-catch this species.