Jack pine budworm: monitoring a species that hides in plain sight

Choristoneura pinus feeds on jack pine, a species grown on poor sites where a defoliation event can wipe out a rotation’s worth of growth. The moth is closely related to spruce budworm and shares several pheromone components, which is the source of a common and expensive mistake: running a spruce budworm lure in a jack pine stand and reading the catch as spruce budworm.

Keep the species apart

The blends overlap but are not identical, and the alcohol component is where the difference shows. A jack pine programme should specify its blend by species and require the isomeric composition in writing, then keep that specification fixed for the life of the monitoring series. Changing supplier or lot mid-series changes the instrument.

Where both species occur in the same landscape — which is common in the northern Lake States and Ontario — run paired traps with the two blends and treat the difference as data. A single trap in a mixed stand produces a number that cannot be assigned to either species.

Stand selection

Jack pine budworm outbreaks are associated with mature stands on droughty sites, particularly where the canopy has begun to open. Traps placed in dense young plantations will read near zero through a real outbreak. The survey should follow the susceptible age class, not the easiest access.

• Target stands at or near rotation age on the driest sites in the compartment.
• Place traps in the upper third of the live crown, on the south or west side.
• Record stand age and stocking with each trap — outbreak risk tracks both.
• Keep trap trees marked; re-hanging on the same tree each year removes one variable.

Season

The flight follows spruce budworm by a week or two in most years, running from late June through July. Because the two flights overlap, a programme that monitors both species needs its check schedule set for the earlier one and its dispensers dated, so a late replacement is visible in the record rather than inferred.

From catch to action

Pheromone catch is the first of three signals. The second is a larval survey — beating trays or branch samples in the upper crown in late summer. The third is defoliation mapping from the air. A programme that acts on trap catch alone either over-treats or, more often, misses the stands where the larvae actually are.

What trap data does well is tell you where to spend the larval survey budget: a stand whose catch has tripled is worth the walk; a stand that reads zero for three seasons is not.

Material and documentation

Lures are supplied against a stated isomer composition with a per-lot certificate of analysis, and the same specification can be held for repeat seasons so the series stays comparable. Development quantities are available for a first season before committing to a multi-year supply.

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 / 50kg with development quantities below that.

Questions this programme usually raises

Can I use one trap for both budworm species?

Not if you need species-level data. The blends overlap enough that a single trap produces a mixed count, and the ratio you use to allocate the catch is an assumption rather than a measurement.

How early in the season should traps go up?

Before the first expected moth — for jack pine budworm, mid-June in most of its range. Traps set after the flight starts miss the peak and understate the population.

Does trap height really change catch?

Yes, substantially in pine. Traps in the upper crown of dominant trees consistently out-catch low traps in the same stand, which is why height belongs in the permanent record.