MANHATTAN, Kan. — If holes mysteriously appear in the buds of home garden flowers, it is likely the work of the tobacco budworm.
“Though a number of flowers can serve as hosts, geraniums and petunias are most commonly attacked,” said Kansas State University horticulture expert Ward Upham.
Upham said that it is the larva of budworms that damages buds. The larva will burrow into buds before they open and feed on the developing flower inside. This feed persists for about a month before the larva drops into the soil to pupate into an adult moth.
Most flower buds that the budworm snacks on will fail to open.
“Those that do open will show evidence of feeding on the petals,” Upham said. “Damage normally peaks in late summer because of increased numbers from the second generation.”
How can budding plants be protected? Upham said control is difficult, but recommended handpicking at dusk on small plantings. “Look for striped caterpillars with variations of colors of green, red, light brown and darker browns – related to the color of the flower they are feeding on,” he said.
For larger plantings, Upham said chemical control may be the only practical option. He recommended products with synthetic pyrethroid active ingredients such as permethrin, esfenvalerate, bifenthrin, or gamma-cyhalothrin.
If organic is preferred, products with the active ingredient spinosad are also effective.
Upham and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes. The newsletter is available to view online or can be delivered by email each week.