Pitfall traps are excellent tools for detecting first activity and monitoring the season-long activity of walking and crawling soil and litter arthropods, especially those that are active at night.
Pitfall traps can be used in sampling programs for row crops, orchards, turf, pastures, woodlands, and landscapes.
What Is a Pitfall Trap?
A pitfall trap is a container that is sunk into the ground so that its rim is flush with the soil surface. Insects and other arthropods are captured when they fall into the trap.
To prevent arthropods from escaping or preying on each other, pitfall traps usually contain a killing/preserving agent such as pet safe anti-freeze, soapy water, or ethyl alcohol.
Many pitfall trap designs are available. The circular and barrier pitfall traps described in this publication were selected for their low cost, ease of installation, and ease of servicing. A circular trap is a single pitfall trap, and a barrier trap consists of an aluminium-flashing barrier with a circular trap at each end.
Because of the channelling effect of barrier pitfall traps, they are much more efficient at capturing arthropods than circular traps. A barrier trap can capture up to six times as many arthropods as a single circular trap.
Installation time is lower for circular traps, but servicing time for barrier traps is no more than for an equal number of circular traps. In most soils a circular trap takes less than five minutes to install, and a barrier trap takes 5 to 10 minutes.
Hard soils increase the installation time because digging the hole takes longer. Either type of trap can be serviced in less than five minutes.
Circular Pitfall Trap:
A circular pitfall trap consists of a permanent 32- ounce cup sunk into the ground and a removable 16- or 32-ounce collecting cup with the same rim diameter snugly nested into the permanent cup. Nesting the cups allows easy servicing and results in far less ground disturbance.
How to Install a Circular Pitfall Trap:
Dig a hole as deep as the permanent cup is high. In softer soils, a golf-cup cutter and hand trowel work well to cut the holes. In harder soils, a posthole digger and digging bar might be needed. Use cups with rim diameters that are the same or slightly less than the diameter of the golf-cup cutter, about 4.25 inches (110 mm).
Poke drainage holes in the bottom of the permanent cup, then install it in the hole, packing soil around it. The rim of this cup should be just below the soil surface. Place a collection cup inside the permanent cup, and pack the soil so that its rim is flush with the soil surface and there are no gaps between the rim and the soil.
Spread debris so that the area around the pitfall trap matches the surrounding soil surface. Pour 1 to 2 inches of killing agent into the collecting cup. To prevent rain from filling the cup and to keep flying insects from being caught in the trap, install a cover made of an 8-inch (20-x-20-cm) plywood square supported by four 16-penny nails.
Barrier Pitfall Trap:
A barrier trap consists of an aluminium-flashing barrier with a circular trap at each end. Use a piece of 1-inch (2.5-cm) wide by 3-foot (0.9-m) long angle iron to cut a 1-inch (2.5-cm) deep slice in the soil.
Tap the angle iron into the soil with a hammer to make the slice. Slide a 3-foot (0.9 m) long length of 4-inch (10.3 cm) wide aluminium flashing into the slice. Bend over the sharp top corners of the flashing to minimize the risk of getting cut. Install a circular trap with plywood rain cover at each end of the barrier.
To prevent arthropods from “sneaking through,” be sure that each trap is in contact with the end of the barrier.
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