Diabrotica undecimpunctata howardi

Adults are distinguished from the western subspecies (Diabrotica undecimpunctata undecimpunctata) by geographic distribution rather than consistent morphological differences; the eastern subspecies ranges east of the Rocky Mountains to southern Nevada, southeastern California, and west to Alberta, Canada. Adults of the species D. undecimpunctata have twelve black spots on a yellowish-green body, though spot patterns can vary. The species is often confused with the striped cucumber beetle (Acalymma vittatum), which has longitudinal stripes rather than spots.

Agricultural fields, particularly those containing cucurbits, corn, sorghum, beans, peanuts, and sweet potatoes. Adults overwinter in protected areas in mild climates and disperse to fields during the growing season.

Eastern North America: east of the Rocky Mountains, west to southern Nevada and southeastern California in the United States, and as far west as Alberta in Canada. Populations spread seasonally northward during the growing season.

Adults are active from spring through late summer, with populations peaking in late summer. One to three generations occur per year depending on region: one generation in northern areas, up to three in warmer regions. Adults overwinter in mild climates.

Larvae feed primarily on roots, stem bases, and sometimes fruit rinds in contact with soil. Adults feed on leaves, flower petals, pollen, and fruit. Documented hosts include corn (Zea mays), peanuts (Arachis hypogaea), squash (Cucurbita pepo), cucumber, melon, sorghum, beans, and sweet potato. Larval growth is significantly greater on corn and peanuts than on squash varieties.

• Zea mays - host (larval and adult feeding)larvae feed on roots, adults on leaves and pollen; major economic host
• Arachis hypogaea - host (larval feeding)larvae cause pod scarring and penetration; primary pest in Virginia-Carolina region
• Cucurbita pepo - host (larval and adult feeding)larval growth slower on squash compared to corn and peanuts
• Cucumis sativus - host (adult feeding)adults vector Erwinia tracheiphila causing bacterial wilt in eastern U.S.
• Erwinia tracheiphila - vectorbacterial wilt pathogen transmitted to cucurbits in eastern U.S.
• Pantoea ananatis - vectortransmitted to corn causing late-season decline disease; endosymbiotic and transovarial association established

Females lay eggs in soil at the base of host plants. Larvae hatch and feed on roots and stem bases, then pupate in soil. Adults emerge and disperse by flight to various host plants. Development rate varies with temperature; gravid females have been observed as early as January in North Carolina when thermoregulation elevates body temperature sufficiently for development. Number of generations per year ranges from one in the north to three in warmer regions.

Adults are strong fliers and readily disperse between fields during the growing season. Both sexes exhibit behavioral thermoregulation by basking in direct sunlight on clear fall and winter days when air temperature is below 13°C, elevating body temperature up to 13.3°C above ambient. This thermoregulation enables flight, feeding, mating, and preovipositional development at temperatures otherwise too low for activity. On cloudy days, body temperature correlates more closely with substrate and ground temperature.

Agricultural pest with significant economic impact through direct feeding damage and disease vectoring. As a vector of Erwinia tracheiphila and Pantoea ananatis, it facilitates transmission of bacterial pathogens to crop plants. The species serves as prey for various vertebrate predators including toads (Bufo americanus, B. fowleri), deer mice (Peromyscus maniculatus), and bobwhite quail (Colinus virginianus), though cucurbitacin ingestion does not appear to confer chemical protection from predation.

Major agricultural pest causing economic damage to cucurbits, corn, peanuts, and sweet potatoes. In the eastern U.S., adult feeding on cucurbits vectors bacterial wilt (Erwinia tracheiphila), which renders plants unmarketable. In snap beans, adult feeding damages pods and interferes with pod set. Larval feeding is the primary damage agent in corn, peanuts, and sweet potato, destroying growing points in corn seedlings and causing direct damage to marketable sweet potato roots. Management relies primarily on preventative insecticide applications, with chlorpyrifos historically used until its 2022 registration revocation; isocycloseram shows promise as an alternative.

• Diabrotica undecimpunctata undecimpunctataWestern subspecies distinguished by geographic range (west of Great Basin) rather than reliable morphological characters; both subspecies overlap in southern Nevada and southeastern California
• Acalymma vittatumStriped cucumber beetle has longitudinal black stripes on elytra rather than spots; both species occur on cucurbit crops and vector bacterial wilt in eastern U.S.
• Diabrotica virgifera virgiferaWestern corn rootworm is similar in size and habitat but has distinct coloration and is also a vector of Pantoea ananatis; co-occurs in corn fields

• agricultural pest
• disease vector
• root feeder
• polyphagous
• thermoregulation
• corn pest
• cucurbit pest
• peanut pest

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Spotted Cucumber Beetle: New Guide Profiles Crop Damage, Management for Polyphagous North American Pest
• Cutting Through the Complexity of Managing Early-Season Crop Pests
• Bug Eric: Fork-tailed Bush Katydid
• Cucurbitacins and predation of the spotted cucumber beetle, Diabrotica undecimpunctata howardi
• Thermoregulation by Diabrotica undecimpunctata howardi and potential effects on overwintering biology
• Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) and Southern Corn Rootworm (Diabrotica undecimpunctata howardi Barber) Identified as Vectors of Late-Season Decline Disease-Causing Pantoea ananatis
• Sublethal Effects of vATPase-A and Snf7 dsRNAs on Biology of Southern Corn Rootworm, Diabrotica undecimpunctata howardi Barber
• Effects of host plant and cucurbitacin on growth of larval Diabrotica undecimpunctata howardi
• A novel insecticide, isocycloseram, shows promise as an alternative to chlorpyrifos against a direct pest of peanut, Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae)