Sunburn or decease?

[KC Kam]

Greetings Orchid Lovers!

I am having some issue with my orchid leaves. I am not sure whether this is sunburn, underwater or decease. Any idea?

Please advice

[Chris in Hamilton]

The left one Oncidium? is probably a humidity issue but if you just re-potted that could be the cause. Don't know how much you are watering the Dendrobium but this time of year, I try to never let mine dry completely. Its producing all of those long roots searching for something else to latch onto, either it has outgrown the mount or the mount has rotted. Just a thought but it might be a good idea to isolate the plant when you have a question. So much happening in your pics.

[raybark]

Could be anthracnose, a fungal disease, or merely "burn" from overuse of fertilizer or accumulation of fertilizer and plant residues in the medium.

How long has it been in that LECA, and does it dry out between watering?

LECA is a great hydroponic medium, but if used in a manner that allows it to dry out, it must be flushed heavily and frequently, as it can "grab and hold" contaminants really well.

[zainal abidin]

Maybe Cecospora as the disease become active during the wet season I had similar experience better cut and apply benomyl.

[Dorsetman]

under-watering at some point - cannot be cured by over-watering at other points !

[KC Kam]

The left one Oncidium? is probably a humidity issue but if you just re-potted that could be the cause. Don't know how much you are watering the Dendrobium but this time of year, I try to never let mine dry completely. Its producing all of those long roots searching for something else to latch onto, either it has outgrown the mount or the mount has rotted. Just a thought but it might be a good idea to isolate the plant when you have a question. So much happening in your pics.

Hi Chris,

Ya, the left was oncidium. As for the dendrobium, I only water once a day and it will dry completely be end of the day. Its roots is moving down the wood..ard 2 feet long...I do have some plan to remount into a new medium.

---------- Post Merged at 11:19 PM ----------

Could be anthracnose, a fungal disease, or merely "burn" from overuse of fertilizer or accumulation of fertilizer and plant residues in the medium.

Hi Ray

How long has it been in that LECA, and does it dry out between watering?

LECA is a great hydroponic medium, but if used in a manner that allows it to dry out, it must be flushed heavily and frequently, as it can "grab and hold" contaminants really well.

It was in the LECA for 4 months and yes, i let it dry out between waterings. I water it with plain water during week days and only fertilize on weekend with low dosage (0.5gram per liter (NPK 21-21-21)

Hmm...seems like it is decease then?

---------- Post Merged at 11:21 PM ----------

Maybe Cecospora as the disease become active during the wet season I had similar experience better cut and apply benomyl.

Hi Zainal,

Ok...i'll cut them then.


Thank you everyone for your advise.

[raybark]

It was in the LECA for 4 months and yes, i let it dry out between waterings. I water it with plain water during week days and only fertilize on weekend with low dosage (0.5gram per liter (NPK 21-21-21)

Hmm...seems like it is decease then?

Likely, but not necessarily.

The reason I asked about drying is that the LECA particles act like a sponge. When watered, liquid (along with any dissolved minerals) hitting the surface is quickly transferred to the interior of the pellet by surface tension, resulting in a fairly uniform distribution throughout. Drying, on the other hand, occurs at the outer surface, and the evaporation rate tends to be faster than the transfer of liquid back to the surface. That means, therefore, that as the solvent (water) is lost to evaporation, the concentration of dissolved solids within the pellet increases, until it reaches saturation and begins to precipitate, both at the surface as well as in the pellet interior. When you water it again, some of the surface precipitate may redissolve (although it is a very slow process - much slower than dissolving the fertilizer powder), but that inside the pellet really doesn't, so you end up adding to it at every wet/dry cycle.

0.5g/L of a 21-21-21 formula, is about 105 ppm N and a the three majors, together, supply about 250 ppm of dissolved solids. If the formula has minor elements as well, the dissolved solids content is even higher. Any dissolved solids in your water supply contribute to the precipitation process, as well.

Chances are that four months of cycling has not resulted in an issue, unless your water has a high TDS to start with and/or you didn't wash the LECA properly, but it's something to keep in mind.

[CattyRobb]

I'd like to qualify this comment by stating that I am not an expert by any means. I will say, however, that many of my plants exhibited these exact same symptoms for quite some time. I thought it was a fungal issue or a calcium deficiency for the longest time. In the end, I researched water/nutrition in many forums and orchid society resources online. My issue turned out to be overfeeding/fertilizer burn. Another good indicator is to see if your new root tips are dying when they come into contact with the medium, instead of taking hold. If you have that going on, as well as the leaf tip die-back, I would give it serious consideration. After also researching my water quality, I discovered that my city water was a little too high in total dissolved solids, as well as being just a little too alkaline for comfort, which can exacerbate nutrition issues. Organic medium also becomes more acidic over time as it decomposes, which can set them back as well. Since switching to distilled water and cutting my feeding WAY back, my plants have been responding very well for many months now. I did also add a seaweed based micronutrient supplement once a month, as distilled and RO water don't have any of them. No issues like this on new growth, and they are all coming on strong, with lots of new root action and multiple new growths per plant. Now I'm getting a second flush of growth on all of them. Give it a thought, as my plants looked just like yours when I was having so many problems. It can cause a slow decline over time. Ray knows what he is talking about when it comes to overfeeding. I give him credit for helping me get my issues straightened out. The amounts you use should change according to your frequency of feeding as well. Either way, it's still probably not a terrible idea to remove the damaged portions with a sterile instrument and treat the cut edges with cinnamon. Fungal infections often take advantage of damaged tissue caused by other issues to use as an entry point, so you can have more issues than one at the same time.

[KC Kam]

Likely, but not necessarily.

The reason I asked about drying is that the LECA particles act like a sponge. When watered, liquid (along with any dissolved minerals) hitting the surface is quickly transferred to the interior of the pellet by surface tension, resulting in a fairly uniform distribution throughout. Drying, on the other hand, occurs at the outer surface, and the evaporation rate tends to be faster than the transfer of liquid back to the surface. That means, therefore, that as the solvent (water) is lost to evaporation, the concentration of dissolved solids within the pellet increases, until it reaches saturation and begins to precipitate, both at the surface as well as in the pellet interior. When you water it again, some of the surface precipitate may redissolve (although it is a very slow process - much slower than dissolving the fertilizer powder), but that inside the pellet really doesn't, so you end up adding to it at every wet/dry cycle.

0.5g/L of a 21-21-21 formula, is about 105 ppm N and a the three majors, together, supply about 250 ppm of dissolved solids. If the formula has minor elements as well, the dissolved solids content is even higher. Any dissolved solids in your water supply contribute to the precipitation process, as well.

Chances are that four months of cycling has not resulted in an issue, unless your water has a high TDS to start with and/or you didn't wash the LECA properly, but it's something to keep in mind.

Hi Ray,

Hmm....is it better to pot in LECA as comparing to charcoal or fern slabs? Initially i tried to avoid traditional mediums because they breaks down overtime which will be a hassle for me during my re-potting process at the same time to save as much roots as possible. My last few experience of re-potting took me around 6 hours. Hence i try to migrate them to pure LECA. Most of my orchids was in LECA now..i realize some of them are slightly smaller in size maybe due to insufficient water (but no wrinkles). Any advice on this?

As for fertilizing, you did advise me previously in one of other members chat but i am unable to trace it back. I hope i am still getting my fert volume right?

I used to water daily with fertz but now i am doing it twice a week..sometimes only 1 time. I was hoping to do it once a week but was wondering whether my plants will grow faster and stronger if i only fert them once a week as compare to twice a week. I am also pondering whether i should put some slow release ferts and only have manual fertz once a week. Any advice on this as well?

Thank you Ray

---------- Post Merged at 01:24 PM ----------

I'd like to qualify this comment by stating that I am not an expert by any means. I will say, however, that many of my plants exhibited these exact same symptoms for quite some time. I thought it was a fungal issue or a calcium deficiency for the longest time. In the end, I researched water/nutrition in many forums and orchid society resources online. My issue turned out to be overfeeding/fertilizer burn. Another good indicator is to see if your new root tips are dying when they come into contact with the medium, instead of taking hold. If you have that going on, as well as the leaf tip die-back, I would give it serious consideration. After also researching my water quality, I discovered that my city water was a little too high in total dissolved solids, as well as being just a little too alkaline for comfort, which can exacerbate nutrition issues. Organic medium also becomes more acidic over time as it decomposes, which can set them back as well. Since switching to distilled water and cutting my feeding WAY back, my plants have been responding very well for many months now. I did also add a seaweed based micronutrient supplement once a month, as distilled and RO water don't have any of them. No issues like this on new growth, and they are all coming on strong, with lots of new root action and multiple new growths per plant. Now I'm getting a second flush of growth on all of them. Give it a thought, as my plants looked just like yours when I was having so many problems. It can cause a slow decline over time. Ray knows what he is talking about when it comes to overfeeding. I give him credit for helping me get my issues straightened out. The amounts you use should change according to your frequency of feeding as well. Either way, it's still probably not a terrible idea to remove the damaged portions with a sterile instrument and treat the cut edges with cinnamon. Fungal infections often take advantage of damaged tissue caused by other issues to use as an entry point, so you can have more issues than one at the same time.

Thank you Robb,

I will double check my water quality and the root tips. I guess my water is fine because i have a membrane filter that filter almost everything but let me double check.

[CattyRobb]

My TDS wasn't super high, but it was too high for the amount I was feeding, as these factors interact. I don't think you ever want to use water with TDS of over 200 if you can help it. Mine was about 185 on average, but I was also feeding way too heavily. If you're feeding every day like I am, I shoot for 12.5 ppm nitrogen, even with distilled water. More frequent watering = more dilute fert. I skip one sometimes too or make it ever weaker, as I am shooting for about 75 ppm nitrogen in total per week, per Ray's advice. Most of us overfeed without even realize we're doing it. Remember the correlation between frequency and strength of solution, and it will help if you're having any of these issues. I also think it's better to fertilize weakly every time you water, instead of say only fertilizing once a month and giving it a heavy dose at one time. It happens in very small increments over time in nature.