Bad winter: leaf spot (bacterium. fungus) or virus?

[Lars Kurth]

This is the third item in the "Bad winter issue series". I am hoping that maybe somebody can help me identify what it is.

I have had a terrible winter in my greenhouse. I was not around much (travelling 3 weeks out of the month for work) for nearly 5 months now and having other people looking after the greenhouse. I often only had a day in between trips and just enough time to wash clothes.

As a consequence I now have a mixture of diseases as well as maybe cultural issues.

Now this one is entirely my fault. I got a huge specimem Stanhopea from my mother as a present in late summer. It had a few of the spots in question. Wasn't vigilant: cut off the leaves and thought this was it. A few weeks later: actually in October within a period of two weeks, I had similar spots appearing on many plants: Stanhopeas, Coelogyne, some fleshy Angraecum, Catasinae, some Lycaste. I sprayed twice with fungicide and the spread of the spots stopped. So I thought this was it. However the spots seem to affect the plants: on the huge specimem Stanhopea, all the pseudobulbs shrivelled. I removed the papyrus from around the bulbs and noticed that similar spots are on the pseudobulbs.

I looked at various sources and it is not really clear to me what this is and how worried I should be. Doesn't quite look like Cercospora, Guignardia or the other fungal leaf spot diseases. It also doesn't look quite like a bacterial leaf spot. The spots look different on different species, but all appeared within the same two weeks

[tucker85]

It sounds like you understand the diseases pretty well. I definately see some leaf spotting fungus problems in a couple of pictures. Other than that I can't tell. Cool weather fungus problems can be difficult to get rid of sometimes. Also when plants become weak from one disease they are suseptible to others. That can lead to a combination of fungus and bacterial infections. I would treat everything with a good quality, wide spectrum fungicide for two weeks in a row and then once a month after that. It wouldn't hurt to use a bacteriacide treatment also. Physan 20 can be used as a bacteriacide but it's not strong enough to be used as a fungicide when the fungus is already established. Good luck.

[Connie Star]

I'm not certain, but some of the pictures, especially #3, 6 and 7 look like they could be from a virus. I am by no means an expert. In the US there is a lab called Critter Creek that you can send leaf samples to and they will test for viruses.
I bought a test kit from Agdia for virus testing at home but I didn't use up the materials before they expired.
Perhaps you have a similar lab in Europe? I think the USDA (Dept of Agriculture) would take a dim view of potential plant viruses being sent from Europe.