Two species of striped cucumber beetle (Acalymma vittatum shown here) are key pests of squashes, gourds, cucumbers, melons, and other cucurbit crops. A new guide in the open-access Journal of Integrated Pest Management reviews the beetles’ biology and current and potential management strategies. (Photo by Whitney Cranshaw, Colorado State University, Bugwood.org)

By Ariela Haber, Ph.D.

The sister species striped cucumber beetle (Acalymma vittatum) and western striped cucumber beetle (Acalymma trivittatum) are key pests on crops in the Cucurbitaceae family, which includes squashes, gourds, cucumbers, and melons. Both are native to North America, east and west of the Rocky Mountains, respectively, north to southern Canada, and south to most of Mexico. Damage from both species can kill seedlings, prevent fruit set, transmit pathogens, and make fruit unmarketable.

Ariela Haber, Ph.D.

In a new paper in the open-access Journal of Integrated Pest Management, my co-authors Anna Wallingford, Ph.D., Ian Grettenberger, Ph.D., Jasmin Ramirez Bonilla, Amber Vinchesi-Vahl, Ph.D., Donald Weber, Ph.D., and I review the biology, life stages, damage, and current and potential strategies for managing these important cucurbit pests.

Adult beetles are notoriously skilled at rapidly finding and aggregating on their preferred crops to feed. Females then lay eggs at the base of cucurbit plants below the soil surface. After hatching, larvae feed on roots, pupate in soil, and emerge as the next generation of adults. A female can lay up to 1,500 eggs over her lifetime. The number of generations per year ranges from one in the northernmost latitudes to three in the south.

Both species can kill seedlings and weaken older plants by feeding on cotyledons, leaves, and stems. They also feed on flowers, which inhibits successful pollination and fruit set. Feeding on the fruit can scar or cause rot, making it unmarketable. Both species vector squash mosaic virus, and the eastern species vectors fungal pathogens that cause Fusarium wilt and black rot. Of particular concern, striped cucumber beetle vectors Erwinia tracheiphila, the causal agent of bacterial wilt. Bacterial wilt can destroy susceptible cucurbit crops, as few infected plants recover or produce marketable fruit. Economic threshold levels for these pests are not well established and differ by crop type, variety, geographic region, and plant age.

The western striped cucumber beetle (Acalymma trivittatum) is found primarily west of the Rocky Mountains in North America, while its sister species, the striped cucumber beetle (Acalymma vittatum), is found to the east. Both are notoriously skilled at rapidly finding and aggregating on their preferred crops to feed. Females then lay eggs at the base of cucurbit plants below the soil surface. After hatching, larvae feed on roots, pupate in soil, and emerge as the next generation of adults. A female can lay up to 1,500 eggs over her lifetime. (Photo by Ian Grettenberger, Ph.D., originally published in Haber at al 2021, Journal of Integrated Pest Management)

Striped cucumber beetle (Acalymma vittatum) vectors Erwinia tracheiphila, the causal agent of bacterial wilt. Bacterial wilt, symptoms of which are shown here on winter squash, can destroy susceptible cucurbit crops, as few infected plants recover or produce marketable fruit. (Photo by Genevieve Higgins, originally published in Haber at al 2021, Journal of Integrated Pest Management)

Growers commonly use synthetic insecticides (organophosphates, carbamates, pyrethroids, and neonicotinoids) to manage cucumber beetles. However, these chemicals can lose efficacy over time as beetle populations develop resistance. Moreover, they can have detrimental effects on non-target beneficial insects, including the squash bees, bumble bees, and managed honey bees that pollinate cucurbit crops. Organic control options (kaolin clay, pyrethrins, and spinosyns) show inconsistent and often limited efficacy. Sustainable control of cucumber beetles on cucurbit crops therefore must incorporate other control measures.

This profile describes candidates for biological control, as well as a variety of cultural and mechanical control tactics that reduce crop exposure to pests. For example, diversified habitats created by polyculture have been found to have lower cucumber beetle populations than cucurbit monocultures. Natural mulches and composts can reduce cucumber beetle interplant movement, support populations of natural enemies that help control cucumber beetle populations, and cycle nutrients into the soil. Row covers prevent beetles from colonizing plants in their early growth stages, when they are most vulnerable. In a number of recent studies, cucumber beetles were highly attracted to traps baited with their male-produced aggregation pheromone, vittatalactone, suggesting that vittatalactone could be used to precisely target these pests.

These approaches show promise in an integrated management program that provides long-term pest control with minimal adverse effects.

Ariela Haber, Ph.D., is a postdoctoral researcher at the U.S. Department of Agriculture-Agricultural Research Service’s Invasive Insect Biocontrol and Behavior Laboratory, in Beltsville, Maryland. Email: ariela.haber@usda.gov.