Pest description and crop damage The adult is a very small fly, about 1 to 3 mm long, and reddish. Larvae are white to orange, very small and difficult to see with the naked eye. They undergo three larval instars: initially clear, then milky-white, then finally an orange color. Pupae, enclosed in a white silken cocoon, are orange but darken as they get closer to adult emergence. The larvae feed on flower buds and shoot tips, causing distorted growth. If the terminal is attacked later in the season, the damage can be more important because the vine may not recover in time to develop a fruiting bud for the following year. Infestation from first generations does little crop damage, but subsequent generations can prevent the formation of mixed terminal buds required for next year's crop. Tipworm is not noted to be a serious pest in southern Oregon beds, but numerous Washington and northwest Oregon beds suffered substantial crop loss from tipworm in recent years.
Biology and life history The cranberry tipworm overwinters in the larval stage in leaf litter. They pupate for a short time at the end of winter and adults emerge from the pupal stage in spring. Mated females deposit eggs on the inner leaves of newly emerging cranberry shoots. Emerging larvae attack tender shoot tips, potentially killing the apical meristem. Multiple overlapping generations are commonplace by mid-season.
Sampling and thresholds Tipworm larvae and pupae are barely visible to the naked eye. Infested uprights can be most easily noted by the peculiar cupping of tips. Presence of visible damage, however, does not mean presence of active insects in the tips. To accurately monitor for infestation, collect random samples of 25 to 50 uprights during mid-May (first generation), and late-June to mid-July (subsequent generations). Tease apart the tips and examine with a magnifying lens or dissecting scope for larvae and pupae. Treatment is recommended if crop loss has been experienced in previous years and percentage of infested tips is greater than 10% for first generation. Treatment timing for insecticides is at peak egg hatch for first generation of tipworm. This is normally early- to mid-May. Of the chemicals currently listed for management, Movento provides the most consistent management, but repeat applications are required for control.
Adequate nutrition following tipworm infestation will aid in the production of side shoots to replace the destroyed terminal bud, especially if damage occurs early in the season.
Management-chemical control: COMMERCIAL USE
- acephate (Orthene 97, 75S, and WSP) at 0.98 lb ai/a. PHI 90 days. Use only prebloom. Do not exceed one application per crop season. Do not tank mix with other organophosphate insecticides. Do not apply to bloom; material is hazardous to bees.
- carbaryl (several brands) at 1.5 to 2 lb ai/a. PHI 7 days. Target first generation tipworm (prebloom). Two to three applications (7 days apart) are recommend for best control. Do not apply during bloom; carbaryl is hazardous to bees. Latex-based formulations such as Sevin XLR Plus are less hazardous to bees.
- chlorantraniliprole (Altacor) at 0.066 to 0.099 lb ai/a. PHI 1 day. Apply at egg-laying stage. Repeat application 10 days later. Do not exceed 2 applications of chlorantraniliprole or > 0.198 lb ai per crop season.
- chlorpyrifos (Lorsban) at 1.41 lb ai/a. PHI 60 days. Do not apply to bloom; material is hazardous to bees. Do not exceed two applications per season. Restricted use material in the Grayland growing area of Washington. RESTRICTED USE IN OREGON.
- diazinon (several brands) at 2 lb ai/a. PHI 7 days. Do not apply to bloom; material is hazardous to bees. Restricted use material in the Grayland growing area of Washington. Depending on pest population may be applied pre- or post-bloom. Populations of tipworm in British Columbia have been noted to be resistant to diazinon.
- spirotetramat (Movento) at 0.13 to 0.16 lb ai/a. PHI 7 days. Material is hazardous to bees; do not apply until after petal fall. This is the best currently available product for tipworm control.