Budworm Pests on Roses

Identification

• Budworms that infest roses commonly are called geranium or tobacco budworms. The insect is a caterpillar that feeds on the buds of numerous plants in addition to roses. The pests have wide host range, including geraniums, impatiens, petunias, nicotiana, ageratum and a number of other annuals. Rose budworms most frequently are seen in areas with mild winters.

Description

• Budworms seen on roses are the larval stage or caterpillars of light-green small winged moths. The female, whose wingspan is 1 1/2 inches, lays single eggs on rose foliage and buds. The emerging worms are light brown, red or green in color, the variation often coinciding with the color of infested buds. The caterpillars are about ¾ inch long and take a month to mature. From the time of hatching to maturity, the pests feed on the buds of the infested flowers.

Damage

• The pests target the ovaries and buds of infested plants. Affected buds either do not bloom at all or have chewed petals upon blooming. Damaged flowers have a ragged, eaten look. Left uncontrolled, the pest population and damage escalates through the growing season, reaching a peak during late summer. The rose or tobacco budworm also is a seriously destructive pest of petunias and geraniums. The caterpillars also feed on open flowers. Although the moths die in winter, the pupa frequently overwinter in dead buds, reinfesting plants again the following year.

Management

• Monitor plants regularly to control infestation in the early stages by targeting the adults with insecticides. Rose budworms are very hard to control once the caterpillars have burrowed within the buds and inner flower areas. Spray plants regularly with the insecticide spinosad and use a systemic insecticidal drench containing imidacloprid once every year as a preventative strategy. Pick off visible caterpillars manually and drop them in soapy water.