Light Trap & Traps per Acre & Spacing
Catches moths
Enter your field area and whether you're monitoring or mass-trapping to get the number of light traps, traps per acre and the grid spacing between them.
Enter your field
Next: set 4 traps ~101 m apart, switch on at dusk for a few hours after egg-laying flights, and count catches to trigger sprays at the threshold.
Light traps attract many non-targets and beneficials — use mainly for monitoring; place away from homes and run only during peak moth activity.
Light traps — key facts
- Total traps
- traps/acre × acres
- Monitoring
- ≈ 1 per 2.5 acre
- Mass-trapping
- ≈ 1 per acre
- Spacing
- ≈ √(area ÷ traps)
- Catches
- moths & beetles at night
- Run time
- from dusk for a few hours
- Caution
- also catches beneficials
- Privacy
- Runs in your browser; nothing uploaded
A light in the field that warns you early
Many of the worst crop pests — stem borers, armyworm, cutworm and their relatives — fly and mate at night, and a simple lit trap pulls them in where you can count them. That nightly catch is an early-warning system: a sudden rise in moths means a flight is on and a wave of eggs and larvae is coming, giving you days to scout and act before the damage shows. Set out enough traps in the right pattern and you read pest pressure across the whole field.
This tool plans that layout: the number of traps, traps per acre and the grid spacing for monitoring or for denser mass-trapping. Switch the light on at dusk for a few hours during peak flights, count the catch, and trigger control at the economic threshold. Because light is non-selective and catches beneficials too, lean on it for monitoring and pair it with the Pheromone Trap, Sticky Trap and Economic Threshold tools for a complete IPM plan.
Catch the early flight
Spot moth build-up before the larvae hit.
Right number of traps
Sized for monitoring or for mass-trapping.
Even grid layout
Spacing that covers the field without gaps.
Time the spray
Act on the catch at the economic threshold.
Frequently Asked Questions
What does a light trap do?+
A light trap uses a bulb at night to attract night-flying moths and beetles — stem borers, armyworm, cutworm and the like — and funnels them into a collection container or onto a kill surface. Counting the catch tells you which pests are active and how their numbers are building, so you can time control before they damage the crop.
How many light traps do I need?+
Traps = traps per acre × acres. For monitoring and scouting, roughly one trap per 2.5 acres is enough to read pest activity; for mass-trapping to actually knock numbers down, go denser at about one per acre. The tool multiplies your chosen density by your area to give the total.
How is the spacing worked out?+
Spread evenly, the spacing between traps is about the square root of the area divided by the number of traps — grid spacing ≈ √(area ÷ traps). The tool returns this so you can lay the traps out in a regular grid that covers the field without leaving gaps or clustering them.
What's the difference between monitoring and mass-trapping?+
Monitoring uses a few traps just to sample pest activity and time sprays — the catch is data, not control. Mass-trapping uses many more traps to physically remove enough adults to cut egg-laying and reduce the next generation. Pick the mode in the tool and it sets the right trap density.
When should I run the trap?+
Switch the light on at dusk and run it for a few hours into the night, when the target moths fly most, especially during peak flight periods of the pest. Running it all night wastes power and catches more non-targets; a few well-timed hours captures the moths you care about.
How do I use the catch to decide on spraying?+
Keep a simple daily count of the target moths in the trap. A sharp rise signals a flight and a coming wave of eggs and larvae — that's the cue to scout the crop and, if it crosses the economic threshold, to spray. The trap warns you early so the spray lands when it works best.
Do light traps catch beneficial insects too?+
Yes — light is non-selective, so traps also catch beneficial beetles, parasitic wasps and other harmless night-fliers. That's the main reason to use light traps mainly for monitoring rather than heavy mass-trapping, and to favour pheromone traps where a pest-specific lure is available.
Where should I place the traps?+
Site them away from competing bright lights, slightly raised above the crop canopy, spread across the field on the grid spacing the tool gives, and over a water or collection tray to hold the catch. Move or add traps near field edges and hotspots where pests tend to enter first.
Can I combine light traps with other traps?+
Yes — a good IPM programme layers tools. Use pheromone traps for species-specific monitoring, sticky traps for small flying pests, and light traps for the broad sweep of night-flying moths and beetles, then act on the economic threshold. Together they give a fuller picture than any one trap alone.
Are the figures exact?+
They're practical planning figures. The right density and spacing vary with the crop, pest, terrain and how you'll use the catch. Treat the output as a sound starting layout, adjust for field shape and hotspots, and refine as your catch records show where pressure is highest.