Budworms on Roses

Appearance

• The tobacco budworm is a small caterpillar with distinct striping and widely variable coloration. These insect larvae can be red, green, light brown, dark brown or gray, with dark lines along their sides. These color variations are related to the color of the host flower. After a month of feeding, budworms drop to the ground, pupate and produce a light-green moth with brown overtones and cream bands, which lays its eggs on another host flower.

Damage

• This rose pest burrows into the developing flower bud, consuming the young petals inside. Affected buds are marred by dark holes and may never open. Flowers that do successfully open may have large holes in the petals or produce an "empty" flower with a wet brown center surrounded by a few uneaten petals. This damage is merely aesthetic and won't hurt the plant itself, but it can ruin the look of a rose crop.

Control

• Tobacco budworm is difficult to control using insecticides and responds best to synthetic pyrethrin chemicals or to products containing spinosad. Natural pyrethrins do not provide the same level of control due to their short period of effectiveness. Gardeners may also use Bacillus thuringiensis, a bacterial pesticide, but this requires the caterpillar to consume the bacteria.

Considerations

• Winter weather kills many tobacco budworms in the soil around rosebushes. However, container-grown roses taken indoors in winter may harbor these pests, increasing the risk of damage in the future. If roses must be taken inside, remove the soil around the plant roots and dispose of it and any buried budworm pupae. Replace this soil with fresh material to keep the plants healthy.