In the insect's early stages of development, the larvae are small enough to tunnel into flower buds and plant stems. The damage by the small larvae as they tunnel through plant stems results in the introduction of various disease organisms into the plant and results in stems that break readily. The budworm overwinters as pupa in earthen cells several inches beneath the soil surface. In areas where winter temperatures dip below 20 degrees fahrenheit, pupa do not successfully survive the winter. However, soil in areas near buildings, especially on the south side, may not reach temperatures low enough to kill the pupa.
Adults normally emerge in late spring.
Budworms can be active year-round in greenhouses and many of these greenhouse infestations may be responsible for some of the budworm pressure in Northern areas where this insect would not normally overwinter outdoors. Budworms can overwinter in the soil of potted plants that were outdoors during the summer months and then taken into the home during the winter. Microclimates around homes and other buildings protected from low temperatures provide niches of survival for overwintering pupa. Polistes wasps also destroy many larvae, but in Western Colorado these natural control agents are inadequate to control infestations of the Geranium Budworm. Insecticidal control of the caterpillar has been difficult since they are quite resistant to most insecticides.