Using Sticky Cards to Monitor for Insects
Updated article December 2010
Updated suppliers list May 2010
(See the new Identifying Some Pest and Beneficial Insects on Your Sticky Cards October 2010
Sticky cards are an important part of an Integrated Pest Management (IPM) program for greenhouse growers. They are a useful tool to alert you to the presence of certain insect pests. Sticky cards will trap the adult stages of flying insects such as western flower thrips (WFT), whiteflies, fungus gnats, shoreflies, leafminers and winged aphids. Remember that mites, mealybugs, scales, and wingless aphids do not fly and will not be caught on the sticky cards. Also, immature stages of thrips, and whiteflies will not be caught on the cards. Sticky cards can often helps you detect early pest infestations more effectively than will intensive plant sampling. By using sticky cards, you can keep track of insect population trends, and make more informed and timely pest management decisions. However, they are only part of an IPM program that includes visual monitoring and the use indicator plants.
Types of sticky cards
Most commonly, 3 by 5 inch sticky cards are used in the greenhouse. Some cards have a grid system that makes it easier to count the insects on the card. Larger sticky cards are also available. Sticky tapes or ribbons can be used to trap out insect pests. As an example, some growers place sticky tape on their irrigation booms to trap out nuisance shore flies in their propagation houses.
Yellow or blue colored sticky cards are commercially available. Blue cards may be more attractive to thrips (and even shoreflies), and may be used to detect low thrips populations on especially susceptible crops. Yellow sticky cards are best used for general pest monitoring.
Some Suggestions on Using Sticky Cards
Use at least 3 to 4 cards per 1000 sq. ft., or a minimum of one card per 1000 sq. ft with additional cards placed near doors, vents, and over insect-sensitive plant species or cultivars. Use clothespins and stakes to vertically attach sticky cards just above (4 to 6 inches) the crop canopy. As plants increase in height, move the sticky cards upward on the stake.
If you are releasing biological control agents with a winged stage, reduce the number of sticky cards used. Adult parasitic wasps will be caught on the traps. Consult with your biological control supplier to determine the number of cards needed for your particular situation. If you are using bumble bees for pollination in tomato crops, reduce or eliminate the use of blue cards. (Bumble bees are attracted to blue cards).
Cards should be monitored weekly to track trends in insect population development. With increasing temperatures and insect development, spot check cards twice a week. More frequent inspections will allow quicker identification of localized infestations where spot treatments may be beneficial.
Change the cards weekly as the cards will lose their effectiveness in insect trapping as their surface becomes coated with debris. You may be able to change their cards less frequently in the winter months because of slower insect development and activity.
The cost of monitoring is primarily due to the time spent identifying and counting insects on the sticky cards and not the initial cost of the cards. In one study, University of California researchers looked at ways that growers may more efficiently use their sticky cards. Yellow sticky cards (4.5 " by 5.4") were placed 50 feet apart in three California greenhouses where African marigold, verbena, geranium, ageratum, dianthus, and petunia were grown. Sticky cards were placed 8 to 16 inches above the crop and researchers changed the cards once or twice a week. (Editor’s note: most growers in New England use 3 " by 5 "cards for insect monitoring).
Western flower thrips, greenhouse whiteflies, leaf miner adults, and winged aphids were caught on the cards. Whitefly catch tended to be uniform, but more aphids and thrips were caught on the bottom half of the cards. There was more variation in trap catch along the length compared to the width of the card. It was suggested to only need to count a one-inch-wide vertical column in the center of each card to estimate the total numbers of insects caught. The researchers concluded, however, that growers should not cut their cards to a 1" by 5" size. Larger cards tend to catch a greater diversity of insects than smaller cards, and trap catches tend to increase with size.
Cards should be placed just above the crop canopy to more effectively trap thrips. Placing cards at bench level tends to catch more thrips compared to card placement at hanging basket or floor levels. Card counts may be higher at the ends of the greenhouse, where the passively carried thrips tend to drop out of air circulation patterns. Under mist propagation, fewer thrips will be caught on sticky cards, as adults are less able to fly, due to the water on their fringed wings. In February, it may be helpful to place cards just above the floor level, to detect any early emerging thrips that have overwintered in greenhouses with dirt or gravel floors.
Tolerance levels will vary depending upon the crop, potential damage, time in the production cycle and whether tospovirues (are present. Some growers use a "working tolerance level" of less than 10 thrips per card per week. If tosporvirues are present, the threshold is as close to zero as possible.
Horizontal placement of cards just above the soil surface is more effective than vertical placement just above the crop canopy, especially early in the crop cycle
Tolerance levels will vary depending upon the crop, soil mix, and time in the production cycle. Some growers use a working tolerance level of five to ten fungus gnats per card per week using horizontal card placement..
Whitefly (WF) populations tend to be aggregated and not uniformly distributed within the greenhouse. You may consider us more cards near whitefly-favored plant hosts such as lantana, flowering maple, hibiscus, rosemary, tomato, chenille plant, and regal geraniums.
Yellow cards will only catch winged aphids. If winged aphids are present, they may have blown in from outside during the warmer months. If winged aphids are present on sticky cards during cooler months, this may indicate that a significant infestation is present on plants or weeds inside the greenhouse. Focus on plant inspection for aphid detection. Winged females usually develop when there are high aphid populations present on plants or if the plants nutritional quality declines. This allows aphids to disperse to plants that are less crowded and are an adequate food source.
Tips on Identifying Insects on Your Sticky Cards
Use a 10x-15x hand lens to see the identifying characteristics of insects caught on the cards. With practice, it becomes much easier to distinguish a shorefly from a fungus gnat or a thrips from a grain of peat moss. (See Figure 1. Insects frequently found on Sticky Traps in Greenhouses and the PowerPoint presentation for more photos and tips. A hands free optivisor ™ helps you see the entire card.
Only winged aphids will be caught on the cards. Their wings tend to be spread on either side of their pear shaped body. Look for two distinct dark spots on their wings. Aphids also have two cornicles or 'tailpipes" at the rear of their abdomen. Sometimes, aphids trapped on yellow sticky cards may give birth to several young aphid nymphs before they die.
Fungus gnats are small, dark mosquito-like flies with grayish wings. Look for a distinctive "Y" shaped vein at the tip of their single pair of wings (See Figure 1). Fungus gnat adults are delicate insects with longer legs and antennae than shorefly adults.
Leafminers are small, robust flies with a noticeable yellow patch on their body. They have short antennae and two transparent wings. Leafminers also have a large cannon shaped structure at the end of their abdomen that they use to puncture plant leaves and lay eggs.
Leafhoppers are slender insects with a wedge shaped body that tapers to the rear. Their wings are held roof like over their abdomen.
Small parasitic wasps may occasionally be caught on sticky cards, especially in greenhouses where there are fewer spray applications even before releases are made. Parasitic wasps usually have elbowed antennae (like ants), and their bodies may be more pointed toward the rear. Many species have clear wings with only one distinct angular vein along the front of each forewing. They may be stout or slender depending upon the species.
Shoreflies Shorefly adults are more robust with shorter antennae than fungus gnat adults. Adult shoreflies have five clear spots on their wings. Shoreflies may be confused with the beneficial hunter fly. Hunter fly wings are uniformly clear (unlike shoreflies).
Thrips will probably be the smallest insect you will see on the cards. Use a handlens to distinguish adult thrips from grains of peat moss and other debris. WFT adults are narrow, 0.04 to 0.08 inches long, with 2 pairs of fringed wings that are held parallel over their body. Females tend to be dark brown and slightly larger than the small, tan or yellow males.
Whiteflies When trapped on the cards, whitefly adults lose their white color and develop an orangish caste. In addition to greenhouse and sweet potato whiteflies, you may occasionally see banded winged whiteflies. Banded winged whiteflies have a grayish tinge when trapped on the cards, due to the two distinct zigzag black bands on their forewings. A few banded winged whitefly have been caught on cards in Connecticut in the early fall (late August to September). They tend to enter greenhouses from outside (ragweed is a host) but have caused no damage on the poinsettias.
There are many different insects in the world. Besides pest and beneficial insect species, you may see innocuous insects, too. If you see large numbers of insects you cannot identify, especially for longer periods of time, consult an entomologist for help in identification.
Keep records of data from weekly inspections of sticky cards. Some sample forms can be downloaded from the UCONN website or you can develop your own. By examing data over a period of time, population trends will emerge. Often, graphing the data is useful to show population trends over time and help decide if controls are needed.
Some Suppliers of Sticky cards and other IPM Monitoring Tools
Buglady Consulting – http://www.BugladyConsulting.com
IPM Laboratories, Inc. - http://www.ipmlabs.com/
Gemplers - http://www.Gemplers.com
Great Lakes IPM - http://www.greatlakesipm.com/
Green Methods - http://greenmethods.com/
This is not an exhaustive listing. No discrimination is intended for suppliers not listed.
suppliers list last updated May 2010
Leanne Pundt, Extension Educator, Commercial Greenhouse IPM Coordinator
Revised December 2010
Baker, J.R. Identification of Insects on Sticky Cards. North Carolina Flower Growers Bulletin 30(1) 12, 13.
Brodsgaard, H.F. 1989. Colored sticky traps for Frankliniella occidentalis in glasshouses. J. Appl. Ent. 107 136-140.
Dreistade, S. H.; J. P. Newman, and K. Robb. 1998. Sticky Trap Monitoring of Insect Pests. University of California Publication 21572.
Gill, S. and J. Sanderson. 1998. Ball Identification guide to Greenhouse Pests and Beneficials. Ball Publishing. Batavia, Ill. 244 pp.
Heinz, K.M., M.P. Parrella, and J.P. Newman. 1992. Time-Efficient Use of Yellow Sticky Traps in Monitoring Insect Populations. Journal of Economic Entomology 85(6): 2263-2269.
Thomas, C. 2005. Greenhouse IPM with an Emphasis on Biocontrols. Available online: http://extension.psu.edu/ipm/resources/pestproblemsolver/greenhouse/greenhouseipm/view
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