Pheromone and attractant traps is the next installment in our series on alternative and biopesticide control approaches. Pheromones are chemical messengers produced by a variety of animals including insects. There are different types of pheromones produced with differing functions, such as, aggression pheromones, trail pheromones, reproduction pheromones and sex pheromones. Sex pheromones are powerful chemical attractants emitted by female insects. These chemicals are detected by male insects to assist them in locating unfertilized females for mating. Pheromones of many insect species have been identified and synthetically reproduced for use in pest management programs. Some pheromones attract only one species of insect, while others (such as the clearwing borer lure) attract several related species.

In pest management programs, sex pheromone traps are used primarily for detection and monitoring purposes. Traps are deployed when conditions are right for insect activity. By regularly checking the traps and recording numbers, you can determine when insect species are present and active. You can also determine when populations have reached a level or life cycle has reached a stage that control measures are warranted. This type of controlled monitoring and decision making increases the effectiveness and efficiency of control measures and reduces the overall use of pesticides. The majority of the sex pheromone traps use a durable trap housing with a replaceable sticky card and a replaceable pheromone source. Figure 1 shows the design of some of these traps.

Figure 1. A sticky trap protected by a plastic housing.

Directions for trap usage and deployment come with the traps and pheromone lures. In general, traps are placed at eye level for flying insects and one trap per 10,000 to 30,000 square feet or one per zone for enclosed production areas like greenhouses. The traps should be deployed at least two weeks prior to expected insect activity and monitored weekly. The sticky traps are replaced as needed and the pheromone lures usually last 30-75 days.

Some commercially available pheromones include coddling moth, corn earworm, beet armyworm, European corn borer, apple maggot, cotton boll worm, fall armyworm, pecan nut casebearer, black cutworm, clearwing borer, lesser appleworm, oblique banded leafroller, and red banded leafroller. One major producer of insect lures, Scentry Biologicals, sells lures for over 100 different insect species.

Another insect trap that many are familiar with are the yellow sticky traps (they also come in blue) (Figure 2).

Figure 2. A yellow sticky trap with insects.

These are usually 3” x 5” or 6” x 8” bright yellow cards with an adhesive/sticky coating on both sides. These cards indiscriminately trap adult flying insects of many species. They can be used to monitor the presence of insect pests, the direction of their arrival, population density in some cases and population dynamics. One BIG caveat with insect sticky traps: since they trap indiscriminately, you must be able to correctly identify the trapped insects to get information from the traps (Figure 3). The most common trap color is yellow; however, blue traps work better for thrips and they are commercially available.

Figure 3: Insects trapped on yellow sticky card: A – fungus gnats, B – thrips, C – winged aphids, D – leafminer fly, E – parasitic wasp, F – whitefly

Sticky traps are seldom used to directly control insect populations except in enclosed environments (e.g. greenhouses, growth chambers). Sticky traps should be located vertically along the long axis just above the plant canopy. As the plants grow, continue to move the traps upward to maintain this orientation with the plant canopy. A general recommendation is to use one sticky trap for every 10,000 ft2 unless monitoring for whiteflies (one trap every 1,000 ft2). If you are growing multiple crops, it is recommended to have at least one sticky trap per crop type within that crop planting.

As a general rule, pheromone traps and sticky traps should be used in conjunction with visual crop inspection to determine when control measures are necessary. Another method of insect trapping uses lures or baits other than sex pheromone lures. In most cases, these are food attractants. This type of insect trapping has been used for years before the advent of specially designed traps. Today, there are multiple traps and multiple lures commercially available. Most are designed for mass collection of insects (Figure 4). There are also many readily found online plans for homemade designs that are effective. Directions for proper use and placement of these traps comes with the device. There are also traps that use light as an insect lure. The most common are mosquito lights and flea traps. ~Dr. Joe Willis

Selected References

Driestadt, S., J. Newman, K. Robb. 1998. Sticky Trap Monitoring of Insect Pests. UC Cooperative Extension. Publication 21572. Frank, S., J. Baker, S. Bambara. 2019. Insects Found on Yellow Sticky Traps in the Greenhouse. NC State Extension Majumdar, A. and T. Reed. 2013. Pheromone Traps for Monitoring Insect Pests. Alabama Extension ANR-1431. Newman, J. 2010. Monitoring with Sticky Traps Can Save You Money. Pheromone Traps. NPIC Factsheet. Wilen CA, Koike ST, Ploeg A, Tjosvold SA, Bethke JA, Mathews DM, Stapleton JJ. Revised continuously. UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries. UC ANR Publication 3392. Oakland, CA.