The spotted cucumber beetle (Diabrotica undecimpunctata), also known as the southern corn rootworm, is a polyphagous leaf beetle species native to North America. It feeds on over 200 plant species across approximately 50 plant families. In late summer fields, “spotties” sometimes seem to be everywhere.
While it causes little or no damage to many plant species, the spotted cucumber beetle inflicts economic damage on several crops, including cucurbits (squash, melon, cucumber), corn, sorghum, beans, peanut, and sweet potato, with larvae feeding primarily below ground on roots and adults feeding on leaves, flower petals, pollen, and fruit. Adults are strong fliers and readily disperse from field to field during the growing season. The spotted cucumber beetle’s broad host range and high mobility make it particularly challenging to study its ecology and manage it as a pest.
In a paper published in September in the Journal of Integrated Pest Management, a team of researchers from across the U.S. and I review the biology, damage, and current and potential strategies for managing spotted cucumber beetle. We focus on the two subspecies most frequently documented as agricultural pests. The eastern subspecies (Diabrotica undecimpunctata howardi) ranges east of the Rocky Mountains, west to southern Nevada and southeastern California in the United States, and as far west as Alberta in Canada. The western subspecies (Diabrotica undecimpunctata undecimpunctata) ranges west of the Great Basin in California, Oregon, Washington, Idaho, and Baja California Norte.
Adults overwinter in mild climates and spread seasonally northward, with populations increasing into late summer. Females lay eggs in the soil at the base of host plants. After eggs hatch, larvae feed on roots, stem bases, and sometimes fruit rinds in contact with the soil. They pupate in the soil and, when they emerge as adults, disperse by flight to various host plants. The number of generations per year ranges from one in the north to three in warmer regions.
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