Iron Blue Dun
The Iron Blue Dun is a slim dark mayfly dry fly built for technical trout during cool-weather hatches, especially on overcast spring and fall days. It supports searches like Iron Blue Dun fly pattern, small dark mayfly dry fly, and best trout flies for selective risers.
Imitates: Iron Blue duns and other small dark mayflies
Quick Reference
- Best Sizes
- #16-20
- Best Season
- Spring and fall
- Best Conditions
- Cloudy days, slick seams, spring creeks, and selective rises
- Water Temp
- 45-58°F
- Recommended Tippet
- 6X
How to Rig It
Fish alone on a long leader or behind a more visible lead dry.
How to Present It
Dead-drift with zero drag over subtle noses and soft current lanes.
Why It Works
Its dark body and fine silhouette match one of the most important small mayfly profiles trout key on in cool weather.
History
A longtime British and eastern-trout staple, the Iron Blue became famous anywhere trout fed hard on tiny slate-colored duns.
Pro Tip
When the sky darkens and trout start sipping tiny duns, downsize first before changing to flashier patterns.
Frequently Asked Questions
When do you fish an Iron Blue Dun?+
Fish it during cool, cloudy mayfly hatches in spring or fall when trout key on small dark duns.
Not sure if Iron Blue Dun is right today?
Get a fly recommendation based on live water temp, flow, sky, and time of day for any river in the US.
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