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How to identify it
- Adults are small flies, about 3.8 mm (males) to 4.2 mm (females) long, dark metallic green to black with brown to black legs. Each front wing has four pale to dark brown bands; in this species the pattern is paler than in its close relative Euxesta annonae and fades from the front edge of the wing toward the rear.[1]
- The flies move their wings and walk in set patterns, especially near other flies of their kind. They sun themselves early in the day, then move into shade as the sun gets stronger.[1]
- The maggots are whitish, turning pale yellow when full grown at about 6 mm (1/4 inch). They are cylindrical, blunt at the rear, with two black peg-like breathing spots on the blunt end, and tapered to a point at the head.[1]
- Eggs are white, cylindrical and less than 1 mm long, laid in groups of 10 to 40, mostly in the silk at the tip of the ear.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Other corn silk flies (Euxesta eluta, Euxesta annonae, Chaetopsis massyla) | These relatives cause the same damage. Euxesta eluta has a clear round to oval spot near the front edge of the wing; Chaetopsis massyla is medium metallic green with yellowish legs and three dark wing bands instead of four.[1] |
| Corn earworm | A caterpillar, not a maggot, that also feeds at the ear tip. Cornsilk flies often lay eggs around the feeding holes earworms and fall armyworms make in the husk.[1] |
| Fall armyworm | Another caterpillar of corn. More cornsilk flies develop in ears already damaged by fall armyworm, but the flies also infest undamaged ears on their own.[2][1] |
Where it lives
Corn silk flies live in tropical and subtropical parts of the Americas. In the United States, modern reports of damage come from Florida and Georgia (plus Puerto Rico); this species is found in Florida corn from Orlando south. It also occurs in Hawaii, but there is no record of it attacking corn there.[1]
Biology and life cycle
Females cannot pierce intact plant tissue, so they lay eggs in damaged, cracked or rotting tissue. On corn they lay mainly in the silk where it comes out of the ear, and also between husk leaves and around holes made by caterpillars. Many females may use the same ear, leaving hundreds of eggs in it, and ears stay susceptible until a few days before harvest.[1]
Eggs hatch in 28 to 42 hours. The maggots feed for 10 to 16 days, then most flip themselves out of the ear and pupate in the top 2 cm (about 3/4 inch) of soil; pupation takes 5 to 8 days.[1]
On sweet corn in Florida, development from egg to adult takes 17 days in May to 34 in December, and adults live 36 to 52 days. Generations overlap, and researchers estimate 16 to 19 generations a year in southern Florida sweet corn.[1][3]
Adults are present year-round in south-central and southern Florida and feed on pollen, sugary plant sap and fluids leaking from damaged plants. Maggots also develop in culled vegetables and fruits, sorghum, sugarcane and weeds damaged by other insects or machinery, but sweet corn and field corn are the preferred hosts and the only crops economically damaged.[1]
Damage and signs
- Feeding turns the silk bronze-brown along the maggots' paths, and heavy infestations clip all the silk inside the husk, leaving poor kernel set. Wet, rotting silk makes ears unmarketable unless the tips are trimmed.[1]
- Maggots also feed on the cob tip, leaving blank tips, and hollow out developing kernels anywhere along the ear. Field corn, with tougher kernels, is damaged less than sweet corn.[1]
- Unprotected sweet corn ears can be made unmarketable, and losses can reach 100% of the crop. Fields with more than 30% of ears infested at harvest are usually rejected for the fresh market.[1][2]
Health risk
The sources describe it only as a pest of corn ears; they mention no harm to people.[1]
Control
Prevention
Check for adults from before tassels push through until harvest, looking in early morning or late afternoon when they rest on the upper stalk and tassel, and check the silk channel for eggs near the husk tip.[1]
Keep them out
In very small plantings and home gardens, cover each ear when silks first appear with a homemade mesh bag (for example, bridal veil material) tied snugly around the middle of the ear. This greatly reduces egg laying without interfering with pollination.[1]
Sanitation
Manage weeds in and around corn plantings, since weeds shelter the flies.[1]
Biological control
Earwigs, mites, minute pirate bugs, lacewing larvae and rove beetles eat the eggs and young maggots, and assassin bugs and spiders catch adults. No parasites of this fly have been found in Florida.[1]
Pesticides
Commercial growers rely on frequent pyrethroid sprays aimed at adults before they lay eggs in the ears. Flies quickly move back in from nearby sugarcane and untreated corn, and populations from commercial fields have become less susceptible to pyrethroids. Bt corn bred against caterpillars gives no protection against these flies.[1][4]
Common questions
- What are the small white maggots in the tip of my sweet corn?
- In Florida and the Southeast they may be corn silk fly maggots, which feed in the silk, cob tip and kernels. Corn earworm and fall armyworm, which also damage ear tips, are caterpillars rather than maggots.[1]
- How can I protect a few rows of sweet corn from cornsilk flies?
- Bag each ear in fine mesh, such as bridal veil, from the time silks appear, tying it around the middle of the ear. The bag keeps flies from laying eggs and does not stop pollination.[1]
Sources
- University of Florida/IFAS Extension (Featured Creatures), “Cornsilk Fly (suggested common name), Euxesta stigmatias Loew, EENY-224/IN381 (G. S. Nuessly and J. L. Capinera; revised April 2013; archival copy).” journals.flvc.org/edis/article/view/120913 (accessed 2026-11-09)
- Environmental Entomology (via NCBI PubMed), “Examination of the pest status of corn-infesting Ulidiidae (Diptera) (G. Goyal et al.; Environmental Entomology 41(5), 2012; abstract).” pubmed.ncbi.nlm.nih.gov/23068169/ (accessed 2026-11-09)
- Environmental Entomology (via NCBI PubMed), “Developmental Studies of Maize-Infesting Picture-Winged Flies (Diptera: Ulidiidae) (G. Goyal et al.; Environmental Entomology, 2017; abstract).” pubmed.ncbi.nlm.nih.gov/28535262/ (accessed 2026-11-09)
- Journal of Economic Entomology (via NCBI PubMed), “Pyrethroid Susceptibility in Field Populations of Picture-Winged Flies (Diptera: Ulidiidae) Infesting Fresh Market Sweet Corn in Florida (Journal of Economic Entomology, 2022; abstract).” pubmed.ncbi.nlm.nih.gov/36026519/ (accessed 2026-11-09)
- iNaturalist, “Euxesta stigmatias taxon page (order and family).” www.inaturalist.org/taxa/330022 (accessed 2026-11-09)