powdery mildew

[caleb]

Think I've identified some powdery mildew on this shrub. Trouble is I don't have any idea what the shrub is. Planted row, definitely not native to the area. Anyone know what it is and/or have any info on the vector for this if the mildew is unique to this plant?

 

[JD3000]

looks like a Euonymus to me and I'll guess either a fortunei or kiaustschovicus

 

[KTSmith]

Looks like the imperfect (asexual) stage of a powdery mildew. Later in the summer you may find tiny brown/black specks amongst the powdery stuff, and those would be the cleistothecia of the sexual stage of this group of ascomycetes. Yeah, individual species and "races" of the fungus can be highly specific with respect to host plant species or variety.
The common view is, or was when I was in plant pathology school, that these spread in wind and rain rather than an active animal vector. Interestingly, this is one fungus whose infection is favored by drier rather than wetter conditions.

 

[caleb]

Thank you both! Is the standard regimen if propiconozol or other foliar anti-fungal what you would suggest as a course of action? I have that stuff on hand, but again, I am not that familiar with Euonymus.

 

[KTSmith]

I'm sure any specific recommendation that would occur to me would also be far past its expiration date. First question I'd have is whether chemical treatment is justified for disease control. Sometimes it is. Then, I'd check with my local coop ag extension folks as to legal treatments. If you are in NC, NC State has (or used to have) excellent extension publications. 'Course I'd be happy to hear what Buzzers from that part of the world do about powdery mildew.

 

[JD3000]

Most powdery mildew are just aesthetic problems but triazole fungicides such as propiconazole usually have labeling for them, at least preventatively