Arthropod Traps for the Home, Garden, & Agriculture
This is the first in a two-part series on common methods to trap and exclude insects and their relatives. This article will focus on ways to attract and trap arthropods for both monitoring and management purposes. The next issue will cover common exclusion devices to keep arthropods out of buildings and away from plants.
To successfully use traps, there are two basic requirements: the arthropods must move, and the trap must hold them after capture. An advantage in using traps is that they can be set in place and left to catch arthropods 24/7 for a period of time. Traps can be attractive or passive. Attractive traps rely on visual and/or chemical cues; passive traps intercept arthropods as they move about.
A blacklight trap attracts a variety of night-flying insects that are visually attracted to short wavelengths, including moths.
Light, color, contrast, and shape are common visual attractants used in insect traps. Light traps are used to detect and monitor populations of moths, mosquitoes, and other insects, including the invasive brown marmorated stink bug. Because many insects are attracted to short wavelengths, or ultraviolet light, traps that include a blacklight lamp are useful in attracting a spectrum of insects, especially noctuid moths (e.g., corn earworm, cutworm, armyworm). For mosquitoes, the addition of dry ice and a fan or suction increases the trap’s effectiveness.
A downside of blacklight traps is a lack of selectivity; if used for monitoring specific insects, the bi-catch (non-target insects) can flood the trap and make it difficult and time-consuming to identify the insects of interest. Blacklight traps can also attract beneficial and aquatic insects important as biocontrol agents and food for wildlife, respectively. The “bug zapper”-style of trap is an example of a light trap used for insect population reduction. After many years of availability, the effectiveness of bug zappers in reducing mosquito and other pest insect populations is still hotly debated.
White, yellow, and blue-colored traps can be visually attractive to insects. Why? Light, bright colors reflect more ultraviolet light, which is attractive to insects. Instead of seeing green color reflected from the leaves of plants as humans do, insects see hues of yellow and blue. The color of reflected light that humans see as yellow (wavelength 500-600 nm) is a major component of light reflected from plant surfaces, especially from new growth. Sticky cards colored yellow, blue, and white can be used to attract and kill flying insects, such as thrips, whiteflies, aphids, and fruit flies. Colored sticky cards can be used to monitor and reduce populations of insects in greenhouses, indoor plantscapes, and some horticultural crops. But all things seem to have their downsides; these colors are also attractive to pollinators. For example, to avoid trapping honey bees in orchard insect pheromone traps, the use of orange versus white colored delta traps decreases pollinator kill. Insects do not see the color orange.
Contrast and shape can also be visually attractive to insects. For example, the brown marmorated stink bug and many tree-attacking beetles are attracted to a black column-shaped trap. The tall, dark shape of the trap simulates the contrast of a tree trunk against daylight. Typically odor lures are added to draw the insects into the trap container once they climb onto or fly into the trap base. The Manitoba trap utilizes a large, dark sphere suspended under a transparent cone for collection of biting flies. The Manitoba trap, and its many variations, mimic moving livestock to the flies.
Bait traps rely on an insect’s sense of smell for attraction. Food, attractive host plant odors (called kairomones), and mimics of insect pheromones (chemicals used for communication within a species) are the most common baits used in traps. To trap pesky European paper wasps to keep them off ripening fruit, a homemade pop-bottle trap containing fruit juice, yeast, and ripe fruit attracts them inside to their death (click here for a how-to video).
A pop bottle trap containing fruit juice and yeast attracts the European paper wasp.
Many fruit-feeding flies are attracted to vinegar-related scents. A homemade trap of a cup filled with apple cider vinegar lures vinegar (drosophila) flies away from egg-laying activity on ripe fruit in the home. The cherry fruit fly is attracted to yeast, sugars, and ammonia; a commercial attract-and-kill product, GF-120, contains these food baits and an ultra-low dose of spinosad insecticide.
The sex pheromone of many moth species has been identified and used in traps to selectively monitor agriculturally important pest species. For example, codling moth (causes “wormy” apples) males are highly attracted to the female’s sex pheromone called codlemone. But alas, only the males are caught in traps, and so it is an effective monitoring tool, but not effective for control.
Beetles, like moths, can be trapped using pheromones. A recent invasive insect to Utah, the Japanese beetle, is effectively trapped with a combination of rose floral scent and the beetle’s pheromone. Bark beetles have been monitored and repelled from valuable conifer trees, such as at cabin sites and in campgrounds, with the use of aggregation pheromones, attractive host plant chemicals, and repellent pheromones. The interactions among bark beetles, their host trees, and behavior-modifying chemicals is complex and not yet well understood; thus, there can be a fine line between attraction and repellency, and use of these chemicals for bark beetle control is tricky.
The color yellow attracts flies, and a shallow yellow pan with soapy water can be used as a fly trap on windowsills.
A linear pitfall trap is used by USU entomologists and turf managers for monitoring billbugs in turf.
In the home, sticky boards placed along baseboards and behind doors and furniture, can be highly effective in reducing populations of active spiders, such as the hobo. Sticky traps can also be placed in locations with high insect activity to trap insects on the adhesive for sampling or control.
Window and water-pan traps can monitor or control flying insects around the home. A window trap is made from a piece of glass attached to a trough filled with soapy water. When placed in an insect fly-way, insects that hit the glass slide down into the trough. Water pan traps are made from a basin painted yellow or blue and filled with soapy water.
There are a variety of passive traps used in natural and agricultural settings. A Malaise trap is an open-fronted tent made from mesh fabric, that traps insects in their fly-ways. Tall pipe-style suction traps are used to sample insects flying over fields. Pitfall traps placed in the ground can be effective for sampling and controlling ground-dwelling arthropods. The pitfall trap consists of a collecting bottle buried in the ground with a funnel placed at the soil surface. A fluid, such as glycerin or ethanol, can be added to kill the insects that fall into the trap. A rain-roof can be added to keep pitfall traps from flooding.
There are many styles of traps; one can be designed to capture most types of arthropods in many situations. Much information can be found online. Many types of traps are sold as insect and spider control devices. Refer to university and other educational websites for recommendations on effective traps; don’t just believe all that you read on a sales website. For those interested in making an insect collection, there are a number of excellent websites that provide tips on insect trapping. Just search online by “how to make an insect collection.” Traps can be a low-cost, low-toxicity method to monitor and reduce populations of insects, spiders, and other arthropods around the home, garden, and in agricultural settings.
-Diane Alston, Entomologist
California Department of Food and Agriculture. IPM Info. Vegetable Research and Information Center, Sacramento, CA.
Majumdar, A. Introduction to insect pest monitoring using pheromone traps. Alabama Cooperative Extension, Auburn, AL.
Pedigo, L. P. and M. E. Rice. 2009. Entomology and Pest Management, 6th edition (784 pp.), Pearson Prentice Hall, Upper Saddle River, NJ.
Stringham, S. M. 2001. Evaluation of two types of tabanid traps. North Carolina Pest News vol. 16, no. 6, North Carolina State Univ. Extension.