Leafrollers · orchard & nursery
Obliquebanded leafroller: a four-component blend and a two-generation season
Obliquebanded leafroller is the case that proves the point about ratios: four components, two generations, and a blend that only works when the proportions are right.
Choristoneura rosaceana is a tortricid with a wide host range — pome and stone fruit, cane fruit, and a long list of nursery stock. It is also, in pheromone terms, a good demonstration of why “the compound” is the wrong unit of purchase. The blend is built from four components, and the ratio between them is the species message.
The blend
Obliquebanded leafroller lures combine (E)-11-tetradecenal with the corresponding acetate and alcohols. Change the acetate proportion and the lure stops behaving like an OBLR lure; add too much of a congener’s component and you begin catching other leafrollers instead. This is why the specification should name the ratio, and why the certificate should state the isomeric composition of each component rather than a single assay figure for the mixture.
Two generations, two check patterns
In most of its range the moth has two flights: an early summer generation from overwintering larvae and a late summer generation that will overwinter. The first flight decides the season’s pressure; the second decides next year’s. A programme that stops checking in August has measured half the problem.
- Traps go up before the first flight, typically late May to early June depending on latitude.
- Check twice weekly through each peak — the peaks are short and a weekly check can land either side of one.
- Keep traps running until catch is zero for two checks in autumn, so the second generation is quantified.
- Record the date of first catch per block; block-to-block differences of a week are normal and informative.
Where to place traps
In orchards, traps sit in the upper third of the canopy, on the windward edge of the block if the block is small, and inside the block if it is large enough to have an interior. In nurseries, the equivalent is the tallest susceptible stock — leafroller moths orient to the top of the canopy, not to the ground.
One trap per block is a common compromise for fruit; three per block is better if the block is the unit of decision. The trap count should match the number of decisions the programme actually makes.
From catch to management
Catch thresholds in leafroller programmes are regional, because the relationship between catch and fruit damage depends on the crop, the cultivar and the summer temperatures. What transfers between regions is the shape of the series: a rising first flight followed by a heavy second flight is the pattern that precedes damage in the following spring.
Traps are also the check on mating disruption: where disruption is deployed, trap catch should collapse. If it does not, either the dispensers are exhausted or the block was not closed properly — and a trap network is the only cheap way to know which.
Documentation
Each component ships with its own certificate of analysis and isomer figures; the formulated blend is documented as a mixture with a stated composition. Where a programme needs to demonstrate that a delivered blend matches a specification, the chromatogram is the evidence, and we supply it per lot.
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.
| Compound | CAS | Class | Recorded targets |
|---|---|---|---|
| (E)-11-Tetradecenal | 35746-21-5 | Aldehyde | Obliquebanded leafroller, Jack pine budworm +2 more |
| trans-11-Tetradecenyl acetate | 33189-72-9 | Acetate ester | Obliquebanded leafroller, European corn borer +4 more |
| (E)-11-Tetradecen-1-ol | 35153-18-5 | Alcohol | Spruce budworm, Tufted apple budmoth +11 more |
| cis-11-Tetradecen-1-ol | 34010-15-6 | Alcohol | lepidopteran, Cydia pomonella +9 more |
Assay and isomeric composition are stated per lot. Packing starts at 1kg / 25kg / 50kg with development quantities below that.
Questions this programme usually raises
Why not buy a single "leafroller" lure?
Because leafroller is a guild, not a species. A broad lure catches several tortricids and then leaves you unable to decide which management response is appropriate.
Do traps work in mating disruption blocks?
They work differently: catch collapses, so the trap becomes a compliance check on the disruption rather than a population estimate. That is still valuable — a block where catch does not collapse has a problem.
How many generations should the trap network cover?
Both, where the species is bivoltine. The second flight sets next spring’s population, and it is the one most often missed because harvest is happening.