Strange disease on my Cattleya leaves

[LJeziorska]

I am looking for some explanation for an strange disease in my cattleya leaves. It is basically decolored to a brown/ black color even dough if is growing a new bulb I still concern

I am attaching some photos...maybe someone can give me a hand with this.

Please help!!


LJeziorska

[tucker85]

If it's soft and mushy, there's a good chance it's black rot. Black rot can move fast and can spread to other plants. I would cut off the black areas, with a good margin into the healthy tissue. I would also buy a fungicide. Home Depot and Lowes carry premixed fungicides in a spray bottle. Spray your plants well, with the fungicide and then, in a week, spray them again. Check your plants regularly to see if you got all the black rot out. Usually it will flare up again somewhere but eventually you should be able to get rid of it. Good air movement in your growing area and making sure the leaves are dry by nightfall, after watering, can help. I also recommend using a fertilizer that contains calcium. Extra calcium builds stronger cell walls that are less susceptible to fungus and rot. Good luck.

[LJeziorska]

Any fungicide will work or I need to buy a special one for orchids ? And when spraying I should only were the black spots are of just all over ... This is the first time this happens to me thanks


LJeziorska

[LJeziorska]

Ok, so this is what I did I cut the leaves were she had the black spots then I put cinnamon in the healthy tissue of the leave because I do not have any fungicide at Home and I wanted to act fast since you said it can contaminate the other plants as well ... I read that cinnamon act like a fungicide hope this helps

[tucker85]

What you've done is fine. I don't have any experience with cinnamon so I don't know how well it works. The spores from the black rot are on the leaves of the orchids and are not visible, so you need to use a fungicide on the entire plant and on plants that were nearby. Any garden fungicide will probably do the job. If you don't want to mix your own, you'll be limited to whatever premixed fungicide you can find in a spray bottle. Don't be discouraged if you see some more rot develop on a plant or two. Eventually you'll be able to get ahead of the situation. Keep your orchids a little on the dry side until you resolve the problem. If you want to isolate the affected plants from your other plants, that might be a good idea also.

[Orchid Whisperer]

I agree with Tucker, it sure looks like black rot. Follow his advice!

[LJeziorska]

Thanks I will! May I ask what can cause black rot? Did I did something wrong or is if something that can happen to anyone .... Sorry I am a beginner in orchids and this is the first time this happens to me


LJeziorska

[tucker85]

Originally Posted by LJeziorska

Thanks I will! May I ask what can cause black rot? Did I did something wrong or is if something that can happen to anyone .... Sorry I am a beginner in orchids and this is the first time this happens to me


LJeziorska

Black rot is a specific type of fungus (Phytophthora cactorum or Phytophthora palmivora). Unfortunately it's one of the worst kinds of fungus to get in an orchid collection. It may not be anything you did wrong. The spores may have come into your growing area on a plant that you bought. When the conditions are right it can spread rapidly. It seems to affect cattleyas the most. There are three lines of defense.
1) Culture- The leaves of the plants should not be wet at night. That's why it's usually recommended to water in the morning so the foliage dries before night fall. Also air movement around the plants is helpful. Not crowding the plants too much and using a fan to move air can help. Fungus can grow in moist areas with very little air movement.
2) Fungicides- Using a fungicide will decrease the amount of fungus spores and make it less likely that the fungus will spread to healthy plant tissue.
3) Health- Healthy plants will be less likely to get fungus although black rot can affect healthy orchids also. Using a fertilizer that contains calcium will help the plant build stronger tissue that is less likely to be affected by rot.

Even with those precautions it's still possible to get black rot on some plants. I get a few isolated cases every year. It often spreads to one or two plants close by. Under my conditions I've always managed to stop it within a week or two but I don't grow indoors so I'm sure what your experience will be. Here's a link to the AOS page.
Black Rot

[NYCorchidman]

Black rot is very aggressive fungal disease.
Cinnamon won't do a thing against it.

I personally do not believe in cinnamon anyways.
At best, they are useful for drying up the cut wounds.
While cinnamon bark does contain some anti-fungal agent, (hence it is so widely talked about and used as home remedy), pouring cinnamon powder just help drys up cut wound, rather than help plants fight disease.

You want to cut off any darkened portions as Tucker mentioned.
I would get a strong chemical if the plant is valuable. If not, watch for now, but if it keeps coming back, then it's best to discard rather than risking the spread of the disease.

Oh, last but not least, make sure you wash your hands good with soap after touching them bare hands.
Disposable gloves help.

Best!

[Leafmite]

If you can't get a fungicide quickly, after cutting off the infected leaf, clean everything nearby very well with isopropyl alcohol (using new cotton puffs or paper towel pieces for each leaf) to disinfect the leaves and pseudobulb. Don't use alcohol on the roots.
Cattleyas are especially prone to this when they don't get enough calcium. When reading about plants and nutrition deficiency, this seems to be a universal symptom of calcium deficiency.
I went through this with my cattleyas and a few other orchids when I no longer had a goldfish pond. I hadn't realized how rich that water was in calcium from goldfish and the fertilizer tablets for the lotus/lilies and how very much orchids needed calcium. All those years of growing orchids and I'd never had a problem and then I lost nearly all my cattleyas. Since I have been careful to provide the cattleyas with a source of calcium, I have not had any problems since. This does spread quickly through a collection if all the orchids have been grown without adequate calcium so do follow what Tucker suggests. Good luck!