Striped cucumber beetles (Acalymma vittatum, StCB; Figure 1A) and spotted cucumber beetles (Diabrotica undecimpunctata, SpCB; Figure 1B) are common North American pests that feed on cucurbit crops, including cucumber, watermelon, squash, and pumpkin. Both cucumber beetle species feed on plant foliage, which puts young seedlings at risk. In addition to feeding, they also spread plant pathogens such as bacterial wilt of cucurbits caused by Erwinia tracheiphila. Overall, damage by cucumber beetles can be categorized by four major components:
- Transplant/seedling death from feeding damage.
- Transmission of bacterial wilt.
- Interference with pollination.
- Feeding damage to fruit leading to reduced marketability.
This fact sheet provides updated management guidance for cucumber beetles affecting cucurbit crops in Ohio. It includes information relevant across cucurbit systems and incorporates current scouting recommendations, economic thresholds, disease risk considerations, and integrated pest management strategies.
Life Cycle and Biology
Both striped and spotted cucumber beetles co-occur during the growing season in Ohio, although striped cucumber beetles tend to colonize fields initially. The adult life stage is often the only observed stage in the field. However, larvae can be found when digging in the soil of cucurbit fields.
Striped cucumber beetles overwinter in northern U.S. regions, surviving under debris and leaf litter (Radin & Drummond, 1994). They are often the first cucumber beetle to appear in the spring, making them a major early-season pest. In mid-May, StCB adults mate and females lay eggs at the base of cucurbit host plants. The larvae hatch, feed on the roots and stems, and pupate below the soil before emerging as adults. These new adults will continue feeding into the fall. Depending on the region, StCB can complete one to three generations per year, with the time from egg to adult ranging from 40–60 days (Haber et al., 2021).
Although spotted cucumber beetles can overwinter in Ohio, survival is generally low compared to StCB. As a result, most SpCB populations originate from adults that arrive from southern regions later in the growing season, causing this pest to become more numerous and concerning as the season progresses (Haber et al., 2023). SpCB populations peak in mid-summer and remain active until temperatures cool in the fall, completing one to two generations per year.
Identifying and Look-Alikes
Striped cucumber beetles and spotted cucumber beetles are the most damaging beetles in cucurbit production. However, several imposters can make correct identification tricky (Figure 2).
StCB are yellow and have three clean black stripes that extend the length of their backs. The underside of their abdomen is black. StCB can be commonly confused with western corn rootworm (Diabrotica virgifera virgifera, WCR), which also have yellow and black markings on their backs. The main distinction between WCR and StCB is the clean black stripes that correctly identify StCB (Figure 2). Female and male WCR are likely to be seen along with cucumber beetles, but WCR are not considered damaging pests.
SpCB are yellow with 12 black spots on their backs and have a yellow-green underside. Another look-alike often seen with cucumber beetles is the northern corn rootworm (Dibroticam barberi, NCR). NCR is distinguished by a green back with no markings (Figure 2).
Damage
The amount of tolerable cucumber beetle damage depends on the cucurbit cultivar and time of the season. For all cultivars, early-season cucumber beetle feeding can defoliate and damage the stems of seedlings. Severe feeding damage can stunt plant growth or induce plant death (Figure 3A). As the season progresses and the plants grow larger, cucurbits are less affected by direct feeding damage. However, both striped and spotted cucumber beetles can transmit bacterial wilt, which causes browning, wilt, and eventual plant death (Figure 3B). Bacterial wilt is transmitted when cucumber beetles consume infected plant tissue, which passes through the digestive tract and then is deposited directly into the feeding wounds of plants via excrement. Some cultivars, such as watermelon, have a low susceptibility to bacterial wilt and therefore can tolerate higher cucumber beetle populations. Other cultivars, such as muskmelon and cucumbers, are highly susceptible to bacterial wilt and have a lower cucumber beetle tolerance (Haber et al., 2021; Haber et al., 2023). For highly susceptible cultivars, managing cucumber beetles is critical for reducing disease incidence in the field, particularly because bacterial wilt has no curative treatments.
When cucumber beetles move into the blossoms, they aggregate to feed on the flower tissue and pollen. When populations are high, this can lead to decreased pollination and deter wild bees from pollinating infested flowers (Leach & Kaplan, 2025; Figure 3C). If infestations continue later in the season, cucumber beetles will feed on the fruits (Figure 3D). This type of feeding leaves behind rough, corky scars on the rind and can thin the rind’s surface. Heavy feeding damage at this stage makes the fruit unmarketable.
Monitoring and Management
Regular weekly scouting for cucumber beetles is essential throughout the growing season. Scouting helps to distinguish between tolerable numbers of cucumber beetles and populations that exceed economic thresholds, indicating when management may be needed to reduce yield loss.
Scouting is easy early in the growing season, when plants are small and beetles can often be found near the base of the plant and on or under leaves. As plants grow and begin flowering, the beetles become attracted by the volatiles produced by cucurbit flowers and subsequently move into the blossoms (Andrews et al., 2007), though they may still be found feeding on foliage. Scouting at this stage involves checking the entire plant, including the undersides of leaves and inside blossoms.
The management action threshold varies based on crop susceptibility to bacterial wilt (Figure 4). For highly susceptible crops, such as cucumbers and cantaloupes, the threshold is an average of 0.5 beetle per plant based on field sampling—equivalent to one beetle per every two plants scouted. Less susceptible cultivars, such as watermelon, can tolerate an average of up to five beetles per plant before management action is recommended. For more crop-specific action thresholds and detailed scouting instructions, please follow the recommendations of the most current Midwest Vegetable Production Guide (mwveguide.org).
Chemical control
Preventive treatments are often applied early in the season to reduce beetle populations as they emerge from overwintering. For young and vulnerable plants, both seed treatments (in direct-seeded crops) and soil drenches at transplant can help reduce early-season feeding damage.
Later in the growing season, insecticide should be applied only after the action threshold is reached. The action threshold depends on the crop. Typically, pyrethroids and neonicotinoids provide the highest level of cucumber beetle control. Biopesticide options, including pyrethrins and kaolin clay, can also be effective at managing these beetle populations in regenerative or organic operations. When insecticides are used, rotating products with different modes of action and avoiding repeated applications of the same active ingredient are recommended best practices to reduce resistance development. For the most up-to-date pesticide recommendations, product rates, and management action thresholds, please review the most current Midwest Vegetable Production Guide (mwveguide.org). Pesticides should be applied in accordance with the label, avoiding applications during peak pollinator activity.
Cultural controls
Several cultural practices can be used to help minimize cucumber beetle damage. Using transplants over direct seeding can help reduce exposure to cucumber beetles when plants are the most vulnerable to feeding damage (Haber et al., 2021, Haber et al., 2023). At the end of the season, remove any debris and mulch to minimize overwintering sites for StCB. If a plant becomes infected with bacterial wilt, cull the plant to avoid cucumber beetles feeding on the infected plant and spreading bacterial wilt to neighboring healthy plants.
Row covers are successful at providing a physical barrier to cucumber beetles, especially early in the season. In some cultivars, such as muskmelon, row covers have shown to decrease transmission of bacterial wilt and increase yield (Caudle et al., 2013). However, row covers need to be removed when cucurbits bloom to allow for their pollination and fruit-set.
There has also been some success using trap cropping to lure cucumber beetles away from the cash crop and then treat the trap crop with insecticide. Although we know more about trap cropping for the striped cucumber beetle, blue hubbard squash can be effective as a trap crop for spotted cucumber beetles (Pair, 1997).
Biological Control
Parasitoids, like the tachinid fly (Celatoria cetosa), and generalist predators of cucumber beetles exist, but their effectiveness varies (Haber et al., 2021; Haber et al., 2023). These natural enemies are rarely present in numbers that can effectively manage populations of cucumber beetles. Reduced-risk spray programs can, however, promote the success of these natural enemies.
Additional Resources
- IPM solutions in fruit and vegetable
(ashleybleach.com)
References
Andrews, E. S., Theis, N., & Adler, L. S. (2007). Pollinator and herbivore attraction to Cucurbita floral volatiles. Journal of Chemical Ecology, 33, 1682–1691.
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Caudle, J. R., Coolong, T., Williams, M. A., Vincelli, P., & Bessin, R. (2013). Development of an organic muskmelon production system against bacterial wilt disease. II International Organic Fruit Symposium, 1001.
ishs.org/ishs-article/1001_27/
Haber, A., Wallingford, A. K., Grettenberger, I. M., Ramirez Bonilla, J. P., Vinchesi-Vahl, A. C., & Weber, D. C. (2021). Striped cucumber beetle and Western striped cucumber beetle (Coleoptera: Chrysomelidae). Journal of Integrated Pest Management, 12(1), 1–10.
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Haber, A., Bekelja, K., Huseth, A. S., David Buntin, G., Musser, F., Ramirez Bonilla, J. P., Taylor, S. V., Wilczek, D., Grettenberger, I. M., & Weber, D. C. (2023). Spotted cucumber beetle/southern corn rootworm: profile of a polyphagous native pest. Journal of Integrated Pest Management, 14(1), 1–18.
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Leach, A., & Kaplan, I. (2025). Cucumber beetles negatively impact pollinator visitation to cucurbit flowers. Ecological Entomology, 50(2), 411–415.
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Pair, S. D. (1997). Evaluation of systemically treated squash trap plants and attracticidal baits for early-season control of striped and spotted cucumber beetles (Coleoptera: Chrysomelidae) and squash bug (Hemiptera: Coreidae) in cucurbit crops. Journal of Economic Entomology, 90(5), 1307–1314.
doi.org/10.1093/jee/90.5.1307
Phillips, B., Nair, A., Escalante, C., Cloyd, R., Meyers, S., O’Malley, P., Egel, D., Johnning, N., Kennelly, M., Phillips, B., Eaton, T., Schuh, M., Jasinski, J., Adair, A., Bonkowski, J., Creswell, T., Deering, A., Foster, R., Guan, W…Welty, C. (2026). Midwest vegetable production guide. North Central IPM Center.
mwveguide.org/uploads/pdfs/00-MW-Veg-Guide-full-draft-20241101_2024-12-03-155909_vgip.pdf
Radin, A. M., & Drummond, F. A. (1994). Patterns of initial colonization of cucurbits, reproductive activity, and dispersion of striped cucumber beetle, Acalymma vittata (F.) (Coleoptera: Chrysomelidae). Journal of Agricultural Entomology, 11(2), 115–123.
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