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Aquilegia Downy Mildewed Leaves

These have not yet sporulated on the underside of the leaf.

The yellowyness is much more pronounced on the top of the leaf.
It is very easy to see the angular edges of these yellow areas, and clearly see how they are delineated by the leaf veins. downy mildew aquilegia leaf aquilegia downy mildew
Now there has been moistness, probably rain, and the DM responds to the warmth and high humidity by growing out of the underside of the leaf. Now it can sporulate to produce millions of tiny, asexual spores.

This external growth may be seen, especially with a hand-lens, as fluffy, downy white (off white) growth.
Hint: keeping leaves that are NOT yet showing any external growth in  a plastic bag with a wet tissue for a time, may encourage growth that you can see. Or rot the leaf.

Hint 2: 'older', wettened, growth may no longer look fluffy, imagine the difference between dry and wet cotton wool. Difficult to see.

Hint 3: Use a camera with macro for a close-up photo, then view at magnification on your computer screen.
Later, affected tissue can turn browner, these darker lesions are easier to see ...but you have missed your chance, a lot of spores have already been released.
Particularly seen on golden or variegated foliage, where it is difficult to see the yellowy patches.
DM hasn't deterred some aphids!
aquilegia downy mildew
Oops, the start of powdery mildew as well as downy mildew on this poor aquilegia leaf. powdery and downy mildew on aquilegia
What are these holes? Slugs have been grazing; the fungal hyphae (fibres) are nutritious, even if the aquilegia leaf is poisonous. Here's a close-up:

Nothing particularly obvious here... yet look what a close scrutiny of the underside shows.
This leaf just looks generally chlorotic, but look how much growth there is on the underside.

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