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How to identify it
- The damage is the best clue, because both adults and larvae are tiny. Look for undeveloped heads, or heads that are gnarled, twisted and cupped inward, along with scarred bracts and twisted flowers.[2][1]
- The larvae are featureless cream to yellowish-orange maggots about 1/8 inch (3 millimeters) long, found at the base of the bracts or feeding at the base of the florets. A 10x magnifier helps find them.[1][2]
- The adult is a tiny tan fly with clear wings, only about 2 millimeters long. Adults live just two to three days and are hard to find in the field.[1][2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Sunflower bud moth | Sunflower bud moth larvae also attack unopened sunflower buds and can deform heads, but they are caterpillars that tunnel into the plant and leave black frass at an entrance hole.[3] |
Where it lives
It occurs from the northern Great Plains to Texas and is most abundant in North Dakota, South Dakota and Minnesota. Manitoba Agriculture also covers it as a sunflower pest.[2][1]
Biology and life cycle
Adults begin emerging in late June and are active into July. Females lay eggs singly or in groups in the small depressions between the bracts of the sunflower bud.[1][2]
The newly hatched larvae move to the bases of the developing seeds or bracts and feed on the plant tissue with rasping mouthparts. They start at the edge of the head and move toward the center, where they do the most harm.[1][2]
Grown larvae drop from the head and burrow into the soil. If conditions allow, they pupate and produce a second generation in August; otherwise they spend the winter in the soil as larvae in cocoons, or sometimes as pupae, and pupate in spring.[1][2]
Damage and signs
Health risk
These sources treat it only as a pest of sunflower heads and do not mention any harm to people.[1][2]
Control
Prevention
Some sunflower hybrids tolerate or resist the sunflower midge better than others; ask a local agronomist or provincial agricultural representative which ones.[1][2]
Crop rotation and varying the planting date can reduce midge populations. Delaying planting until late May may avoid the first major emergence of overwintering midges, although later infestations can still be severe.[2][1]
Pesticides
There are no economic thresholds, and insecticides do not work well. The larvae crawl into the bud soon after hatching, out of reach of sprays, and a spray could only work if applied just before the adults emerge, which cannot be predicted.[1][2]
Common questions
- Why are my sunflower heads twisted and cupped?
- Gnarled, twisted heads that cup inward and set few seeds, especially along the field edge, are typical of sunflower midge damage. Look at the base of the bracts and florets for tiny cream to orange larvae.[1][2]
- Can I spray for sunflower midge?
- Spraying is not effective. The larvae are protected inside the bud soon after they hatch, and adult emergence can't be timed well enough for a preventive spray.[1][2]
Sources
- Manitoba Agriculture, Government of Manitoba, “Sunflower Midge.” www.gov.mb.ca/agriculture/crops/insects/sunflower-midge.html (accessed 2026-11-09)
- South Dakota State University Extension, “Chapter 11: Sunflower Insect Pests, P-00205-11 (A. Varenhorst, P. Rozeboom and P. Wagner, July 2021).” extension.sdstate.edu/sites/default/files/2021-08/P-00205-11.pdf (accessed 2026-11-09)
- Manitoba Agriculture, Government of Manitoba, “Sunflower Bud Moth (J. Gavloski, revised January 2025).” www.gov.mb.ca/agriculture/crops/insects/pubs/sunflower-bud-moth-revised-january2025.pdf (accessed 2026-11-09)
- iNaturalist, “Contarinia schulzi taxon page (order and family).” www.inaturalist.org/taxa/1584720 (accessed 2026-11-09)