Tobacco budworm

Tobacco budworm larvae bore into unopened rose buds and flower petals, creating oblong to round holes that expand as flowers open. You will see dark caterpillar droppings (frass) inside flowers or on petals. Mature larvae reach one inch long and are tan to green. A single larva can destroy multiple flowers per day, causing rose bushes to cease blooming when populations are high.

Scout plants at dusk when larvae are active, looking for frass and entry holes. Hand-pick and destroy infested buds and larvae. Remove nearby weeds that serve as alternative hosts. Spinosad or Bt applied to buds and flowers provides suppression. Repeat applications every seven to ten days as needed.