Cucumber beetles found in cornfields

May 25, 2016 10:00 AM
Blog Post

Yesterday, I was asked to help confirm an identification of a few beetles in a cornfield near State Center, Iowa. They ended up being striped and spotted cucumber beetles. Sometimes the striped cucumber beetle can be confused with western corn rootworm; however, it would be unlikely to see adult rootworms in May. Spotted cucumber beetle is also known as southern corn rootworm (I suppose it depends on if you grow corn or pumpkins). These beetles were feeding on giant ragweed and burcucumber, a weed Dr. Hartzler blogged about last year.

Striped cucumber beetles found on giant ragweed this week. Photo by New Century FS.
Spotted cucumber beetle (southern corn rootworm) are yellow with a dark head and have 11 black spots on the forewings. Photo by Jim Jasinski,
Striped cucumber beetles are yellow with a dark head and have three crisp, dark lines on the forewings that extend all the way to the wing tip. Photo by Jim Jasinski,
Western corn rootworms are yellow with a dark head. Females have three black lines on the forewings that do not extend to the wing tip. The forewings of males often look like a black smudge (note one male in this photo). Photo by Purdue Extension.

Dr. Laura Jesse, Director of the Plant and Insect Diagnostic Clinic, confirmed striped and spotted cucumber beetles can overwinter in Iowa. They overwinter as adults and emerge in the spring to feed and mate. It is not fully understood where striped and spotted cucumber beetles overwinter or how susceptible the adults are to cold winter temperatures.


Erin Hodgson Professor

Dr. Erin Hodgson started working in the Department of Entomology, now the Department of Plant Pathology, Entomology, and Microbiology, at Iowa State University in 2009. She is a professor with extension and research responsibilities in corn and soybeans. She has a general background in integrated...