Nasty brown spots on Den.

[bloomin_aussie]

Well one of my Den. densiflorums is not looking so good at the moment. OK, I think this came about as a result of me stupidly doing some watering on a couple of hot summer evenings. I am pretty sure it is a fungal infection of some sort. Anyway I've separated this from my other plants but I'm not sure what action to take. The affected area on the plant at the moment is on older growth... leaves on a couple of old canes which don't look too bad and the very badly affected leaves on this cane from the last season's growth. It seems to have spread to the cane a little too. Both of the new growths look completely clean and healthy.

So what do you recommend doing? Should I cut back all the affected parts? Dose it in fungicide (already done - note the white residue on the leaves)? Or do you think it should be given a viking funeral? I do have another division of this plant which has not been affected at all so I am not too worried. I would however like to see if this can be cured... for future reference, not necessarily for this plant's sake. <br><br>Post edited by: bloomin_aussie, at: 2009/04/03 01:58

[Hakulady]

Have the spots increased in number or size? I'm not sure about watering at night but I have automatic watering on my summering dends that water even before the sun comes up. However, the rest of the day allows the moisture to evaporate and therefore I have not noticed anything like these brown spots on my dends.

You may want to check out this website about a fungal problem that affects young dendrobium orchids:

http://www.extento.hawaii.edu/kbase/Crop/Type/f_prolif.htm

that deals with the possible cause of spots on dendrobium orchids. There is a photo in Figure 1 that looks similar to your problem.

Hope this helps.

[bloomin_aussie]

Yes, I came across that site myself and the description and pictures seem quite similar. Unfortunately it says that it is almost impossible to get rid of it once it has infected a plant. Well, first thing I'll try is pruning off the affected parts but if the new growths start showing symptoms I may have to call in a napalm strike. Better check the rest of my plants too.

[Hakulady]

Isolate this dend and keep a sharp eye on it. Removing all the affected leaves could be a last resort. Good luck!

[bloomin_aussie]

Already done. I'm checking it every day to see how things are progressing. The new growths still seem to be unaffected but the leaves on this cane have started to yellow. I'll keep with a regular fungicidal treatment to see if that will help any.

[Aprilmaker]

Do you have any friends that are doctors. Hospitals have labs that can take a sample of the pathogen on the leaf & observe under a scope. Some fungi damage can look similar to others. And also when spraying with any fungicide always incorporate a sticker so it will properly cover the affected area. Your photo looks like a copper fungicide.

[bree]

bloomin aussie- do the new growths also have it or just the older ones?

[Roy]

This leaf spotting is not uncommon on these types of Dends, It can occur with high humidity, stale air, or in can be just weather conditions. I have found this problem to occur mainly if I had my plants too hot or in hot weather. Change its location into a cooler environment and more air. Don't water over head.

[bio_new]

The 1st post was on 2nd Apr 2009, and today is Sept 09. bloomin_aussie may not aware of these new replies.

Anyway for everyone's knowledge, I think we shouldn't stop this discussion though the replies may be belated.

I agree with Roy, this black speckling or spotting is not uncommon in many orchids, especially dendrobium. Generally they are not serious though unsightly. Regular regime of fungicide with removal of infected leaves can achieve good control.

[bloomin_aussie]

Thanks guys, luckily I get an email alert about new posts

I decided to trim all the affected leaves, some of them yellowed and fell off themselves. With all that foliage gone none of the other growths show any signs. The plant seems happy at the moment and I will see what this years new growth looks like.

One of my Cyms was quite badly affected by a similar infection which seems to have been introduced by mite attack. I'm happy to report however that it has produced a decent flower spike (pics to come) and has put out 2 new growths.