Masd. "speckled treasure" black mottling on leaves
 

Hi Folks

I'm having a leaf problem with a Masd. "speckled treasure". I took the plant over from a friend a few months ago and it had a lot of black spots on the leaves. Over time this has evolved into what you see in the image below. Only on some leaves though. In addition to the obvious mottling, there are patches of tiny semi-translucent white spheres (eggs?) on the top surface that are only visible with a magnifier. Any ideas what's going on?

I don't grow Masdevallia but nobody else stepped in. The translucent white things are likely eggs. Treat the plant (spray or wipe) with 70%-90% isopropyl alcohol from a druggist's.

The black spots - I don't know. They could be mechanical damage from too-low humidity, too much sun, insect damage or too much heat. They could also be infectious, caused by fungi, bacteria or viruses.

If you have a university or agricultural agent nearby, take the leaf there and see whether they can figure out what that is. You can't really treat until you know what it is.

Most Masdevallias need cool temperatures, very high humidity, good air circulation and moderate light. Without proper conditions many orchids develop all sorts of problems quite fast.

Quite often Masdies will develop black spots due to heat stress. They can drop the leaves from streaa as well. But the pests may be playing a role also. Hard to tell from the photo. As mentioned, I would get the pests treated and dealt with. Masdies prefer to stay moist, cool and not too much light. They prefer high humidity also, but if other conditions can be met, 50% would likely be OK.

Thanks for the replies. :)

I've done my best to provide the right conditions, temp., light, humidity. Since I've had it, it's put out five new leaves. However one of these didn't open properly and, on closer inspection, it too had black areas. I removed it. The other four are fine. I wiped down all the remaining leaves with a neem solution.

How are the roots? I only have one Masdie now because in summer in my greenhouse I couldn't keep it cool enough so I killed or sold the other ones. But some of my leaves didn't open fully either. I think it is a humidity/moisture issue. You may have to treat more than just the leaves if you have pests. They can get in the stems, roots and media depending what it is. I prefer spraying it well with Malathion and following up a week later to get any hatched eggs. It stinks but it works for most pests.

What you're describing suggests insect damage or infection. I haven't heard of thrips in collections in Canada but what do other people think?

I've never had problem or even seen a thrip in my orchids but they can be seen in outdoor blooms so if any plants were outside or bought in a nursery then I think it is possible to have them here. Thought they mostly bother the blooms only. But can't speak from experience. Now scale, is another thing, I do know of :(

I haven't had a look at the roots since I transplanted it about 4 months ago (haven't had the heart to disturb them). They looked OK then. When I took it over it had black patches and spots, but nothing like the picture.

I only noticed white patches on the leaves about a week ago. When I looked at them under my little pocket "microscope" I saw they were made up of tiny white spheres. Also, there were some slightly larger orange spheres here and there. :confused: I didn't see any "adults".

It's potted in fir bark and I've currently got it in a small fish bowl sitting, slightly raised, above some decorative gravel in water. I've measured the RH inside the bowl at 84%. Outside the bowl the RH is ~70%. It's located in an east facing bay window and gets filtered light for most of the day, with short periods of direct light. Temperature is 19 degrees C (66 degrees F) day and 16 degrees ( 61 degrees F) at night. I water it every 3 days.

I think I may have solved the question, in part anyway. Looking at the underside of the affected leaves with the magnifier, I can see small areas of webbing - mites! No adults though.

I've isolated the plant and will continue wiping the leaves down with a neem/detergent mixture every few days.

Wish me luck! :)

We have 4 'white plagues' of which cushion scale is one. They are a right royal pain in the butt.