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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Invasive Insect Biocontrol & Behavior Laboratory » Research » Publications at this Location » Publication #428309
Research Project: Sustainable Insect Pest Management for Urban Agriculture and Landscapes

Location: Invasive Insect Biocontrol & Behavior Laboratory

Title: Indole synergizes the striped cucumber beetle (Coleoptera: Chrysomelidae) response to aggregation pheromone without attracting pollinators

Author
item KAPLAN, IAN - Purdue University
item GRETTENBERGER, IAN - University Of California, Davis
item HABER, ARIELA - Former ARS Employee
item JEAN, SETH - University Of California, Davis
item KUHAR, THOMAS - Virginia Polytechnic Institution & State University
item NUNEZ, DEMIAN - Virginia Polytechnic Institution & State University
item Weber, Donald
item YOUNGBLOOD, RACHEL - Purdue University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2025
Publication Date: 1/11/2026
Citation: Kaplan, I., Grettenberger, I.M., Haber, A.L., Jean, S., Kuhar, T.P., Nunez, D., Weber, D.C., Youngblood, R. 2026. Indole synergizes the striped cucumber beetle (Coleoptera: Chrysomelidae) response to aggregation pheromone without attracting pollinators. Journal of Economic Entomology. 119(2):982-993. https://doi.org/10.1093/jee/toaf349.
DOI: https://doi.org/10.1093/jee/toaf349

Interpretive Summary: Cucumber beetles are some of the most serious pests of cucurbit (squash, pumpkin, melon crops) in North America. Use of species-specific attractants including pheromones and plant volatile odors would enable behavioral control as an environmentally friendly pest management tactic protective of non-target species including pollinators vital to the crop. However, vittatalactone, the aggregation pheromone of the striped cucumber beetle, is not available commercially, and is expensive to synthesize. Volatile floral aromas from cucurbit flowers are also attractive to these pests, and are inexpensive. But, the floral blend also attracts pollinators, which is a negative side effect. We tested indole, a single component of the floral aroma, and found it to synergize pheromone attraction to the pests, yet unattractive to pollinators. This combination of attractants thus constitutes a cost-effective tool for behavioral pest management. The results will be of interest to cucurbit researchers and pest managers, as well as pheromone providers, to provide behavioral pest control for protection of this important group of vegetable crops.

Technical Abstract: Deploying semiochemicals in pest management can be complicated for pollinator-dependent crops, especially when floral-based attractants are used that may inadvertently distract or kill bees and other pollinating insects. Cucurbit crops, for example, are highly dependent on pollination and their primary pests, Acalymma vittatum (striped cucumber beetle, StCB) and Acalymma trivittatum (western striped cucumber beetle, WStCB), are strongly attracted to the scent of cucurbit blossoms. To identify a more pollinator-friendly semiochemical lure for striped cucumber beetles, we conducted a two-year field experiment across four U.S. states (IN, MD, VA, CA) that evaluated pest responses to: i) a cucurbit floral mimic (TIC), ii) indole, a single component of TIC; and iii) vittatalactone, an aggregation pheromone isolated from StCB. These compounds were tested both individually and in combination to test for non-additivity (i.e., synergistic attraction). In addition to striped cucumber beetles, we also assessed responses from two secondary pests—Diabrotica undecimpunctata (spotted cucumber beetle, SpCB), Diabrotica virgifera virgifera (western corn rootworm, WCR)—and pollinators (Apis mellifera, honey bees; two wild bee genera, Eucera and Lasioglossum). We found that vittatalactone, but not TIC, was a strong and consistent attractant of Acalymma species (StCB and WStCB), whereas the reverse pattern was observed for Diabrotica species (SpCB, WCR). As expected, TIC—but not indole or vittatalactone—attracted pollinators. Pest trap catch was almost always highest with combinations of vittatalactone and either indole or TIC and this increase was synergistic in 33% of cases. These data suggest that combining indole with vittatalactone results in a potent pest attractant without simultaneously attracting bees, making it a pollinator-friendly pest lure for cucurbit IPM.