Trap Catch Threshold & Spray or Monitor
Monitors moths
Enter the total catch, the number of traps and the action threshold per trap to get the average moths per trap and a clear decision — spray at or above the threshold, or keep monitoring.
Enter your trap catch
Next: average catch is at or above the 8/trap threshold — time a spray to the pest's vulnerable stage and re-check traps after a few days.
Pheromone-trap thresholds are species- and crop-specific and indicate adult flight, not larval damage. Calibrate to your local advisory's action level.
Trap catch threshold — key facts
- Average per trap
- total catch ÷ traps
- Spray
- average ≥ threshold per trap
- Monitor
- average < threshold
- Threshold
- set by pest and crop guidance
- Averaging
- smooths a single hot trap
- Check traps
- once or twice a week
- Trap types
- pheromone, light, sticky
- Privacy
- Runs in your browser; nothing uploaded
Spray when the catch crosses the line, not before
Pheromone and other traps turn an invisible pest flight into a number you can act on. But a single trap is noisy, and spraying every time you see a moth wastes money and beneficials. The smart move is to average the catch across your traps and compare it to a published action threshold — spray only when the population reaches the level that justifies it. This tool does the averaging and the call.
It gives the average per trap, the spray-or-monitor decision, your total catch and the threshold from the catch, the trap count and the threshold you enter. Use it to time sprays precisely, cut needless applications, and slow resistance. Pair it with the Nematode Threshold, Weed Density Survey and Leaf Wetness Disease Risk tools for a full crop-protection plan.
Time sprays precisely
Act the moment the catch crosses threshold.
Cut needless sprays
Monitor below threshold instead of spraying.
Smooth out hot traps
Averaging gives a fairer field-wide read.
Slow resistance
Fewer, better-timed sprays ease selection pressure.
Frequently Asked Questions
How is the spray decision made?+
By the average catch per trap against the action threshold. Average per trap = total catch ÷ number of traps. If that average reaches or exceeds the threshold per trap, the tool says spray; if it is below, it says monitor. Averaging across traps smooths out a single hot trap and gives a fairer read of pest pressure.
Why average across traps?+
One trap can sit in a hotspot or a dead zone, so a single count is noisy. Averaging several traps across the block gives a more reliable measure of the moth flight. The tool divides the total catch by the number of traps so your decision rests on field-wide pressure, not one lucky or unlucky trap.
What is an action threshold per trap?+
It is the average catch at which spraying is justified — published for many pests as moths per trap per period. Below it, the expected damage does not pay for control; at or above it, treatment protects more value than it costs. Use the threshold from guidance for your specific pest, crop and trap type.
Why spray at or above the threshold, not before?+
Spraying below threshold wastes product, money and beneficial insects on a population unlikely to cause economic loss, and adds resistance pressure. The threshold marks where damage risk crosses the cost of control, so acting at or above it targets sprays where they actually pay. Below it, monitoring is the cheaper, smarter choice.
What does monitor mean here?+
It means keep the traps running and recount on schedule rather than spraying now. Catches build through a flight, so a below-threshold average today can cross the line in a few days. Monitoring catches that rise early and lets you time a spray for the moment it becomes worthwhile.
What kind of traps does this use?+
It works with any traps reported as a count per trap — pheromone traps for moths are the classic case, but light, sticky or bait traps fit the same maths. The key is that the threshold you enter matches the trap type, lure and pest the threshold was set for, since catch rates differ between trap designs.
How often should I check traps?+
Typically once or twice a week through the pest's flight period, replacing lures and sticky liners on schedule so catch rates stay comparable. Consistent timing and maintenance keep the averages meaningful; a clogged or expired trap under-counts and can hide a real outbreak.
Does weather or crop stage change the threshold?+
The trap threshold itself is usually fixed by guidance, but crop susceptibility and weather affect how a given catch translates to damage — a vulnerable growth stage or warm, fast-developing conditions raise the stakes. Use the calculator for the catch decision and factor crop stage and forecast into the final call.
Are the figures precise?+
They're solid working figures for a spray decision. Trap catches vary with weather, trap placement and lure age, and thresholds are guidance rather than hard cut-offs. Treat the result as a strong signal, confirm with scouting for actual damage, and follow local recommendations before spraying.