Is there any way I can confuse the two at this time of year?.... I think we've got endemic white rot on my new site .... but one reason for thinking it might be mildew is that there's an allium weed of some description that is perfectly susceptible to it all over the site.... if it's white rot I wouldn't expect an allium weed (some sort of wild garlic thing) ......
I don't think so mildew looks like a off white powder that forms on the leaves and white rot is a white fungi that forms on the roots of the onion
As dayyw1 says,
downy mildew is a pale white / grey fungus that coats the leaves. It is highly visible.
White rot is not visible as all the action is happening underground. The only indications tend to be a sick looking plant which can often be pulled up without any effort because the roots have rotted. As well as rotting roots the underside of the bulb has usually also started to rot.
White rot is much more serious. Downy mildew can (and often does) happen site-wide while white rot is more likely to be plot specific.
Yep.... couldn'tr remember what downy mildew was really like.... looks liek white rot is endemic on our site.... I'm putting up a flyer and expect my phone to be ringing off the hook....
chrisc