Sneaky downy mildew
Downy mildew is a horrible sneaky disease, obviously a lover of our climate and not many others, as a lot of books don’t even mention it. Sneaky because in its mild form you hardly notice it, or think it’s just a bit of blackspot. And it can kill!!! Last year my sister’s roses up north were nearly wiped out by it as she refused to spray until it was, in a lot of cases, too late.
Downy mildew looks a bit like blackspot and nothing like mildew(powdery). On close inspection the spots are more brownish red than black, and the leaves don’t usually go yellow like they do with blackspot. The small, speckly spots also spread onto the flower buds, causing them to wither, and also onto some of the stems.
Downy Mildew susceptibility
As with all diseases, some plants and positions are more prone to downy mildew. The yellow and apricot roses seem particularly at risk. They will be the first to succumb It spreads like crazy and pretty much anything can get it to some extent. It is most rife in spring. However, there is a bit of it in the garden now, in early winter, as it has been raining heaps and is still relatively warm. Spraying will not eradicate it, but will keep it right down to barely noticeable levels. The thing you have to do, is make sure you are using a spray that kills it, as a lot of them don’t. . (Last season here in the Northern Waikato, it never showed it’s hideous spotty face, and I thought maybe it wouldn’t be a problem here, but alas it just wasn’t in the mood in 2015…)