brown rot pandemic

[Mathias]

I have had exactly the same problems as you show in your pictures. In my case I believe it was/is a deficiency of Ca or Mg. I had used an organic fertilizer that turned out to be high in K and low in Ca/Mg in combination with RO-water. The Ca that was in the fertilizer was in a slow release form. I have used K-lite and MSU for a few months ans added well water and things have improved. Hopefully I will have nice growths coming now in spring.

 

[Bjorn]

Hello,

The bleach (and I used a higher concentration than suggested!) did not seem to hurt the plants at all. I haven't noticed any improvement in leaf color due to the Ca/Mg or move into the sun. It does look like the growths are a bit stiffer though.

Hope that helps.

I am on a regularly basis troubled with similar symptoms on my cattleyas, but not only new leads, also older mature leaves can get it. It seems normally to be the last one though. I do not think that it is a deficiency, I am more leaning towarsd pseudomonas as didioki has pointed out. The fact that bleaching helps, points in the direction of some pathogen. The link to mineral deficincy may be that with e.g. too high potassium, the natural resistance of the plants are weakened and the outbreak gets more virulent. Although I have it regularly, I do not consider it a major problem, simply because it does not spread that much.
Guess we should pay more attention to the plants immune system, and that is probably the main benefit from reducing K and boosting Ca and Mg. Personally I add Si to that list, you may check my threads on that matter.

 

[TyroneGenade]

Interestingly, at our last orchid meeting there was a plant pathologist and he exclaimed that behind leaf spotting, rot etc... he almost always found that the plants had a magnesium deficiency. Perhaps you should be misting your plants with a Mg solution? Or working some Mg carbonate into the substrate?

 

[Bjorn]

They are all mounted so it must be as solution. I did that previously, but the situation was exactly (or worse) adding Mg-sulphate. For the last year or so K-lite has been used.

 

[Trithor]

Hi Tyrone,
I have been reading this thread over the last few days, and was saddened to find out about your problem and the resultant losses. I hope the problem corrects itself.
I had a similar situation about 18 years ago. I nearly lost my whole collection. When it was over, I was so disillusioned that I gave the remaining plants away, and stopped growing orchids for about 12 years.
I hope your situation does not have a similar effect on you. I now tend to overreact to any potential rot problem, quarantine affected plants and treat the whole greenhouse as if they are all affected.

 

[TyroneGenade]

Well, this morning I had a look at the Trick or Treat and again, some young new growths had rotted centres so the problem hasn't gone away. Seems the bleach was the major factor in getting some good growths. It is still only the new growth and leaves which are affected. My Dendrochilum wenzelli is shooting now so back to the bleach for a bit... Its pushing out 6 new growths from two leads so I don't want to loose this one. Its doing so well... all things considered.

Trithor, I am unlikely to give up. I just need some hope for the fight.

 

[Rick]

Interestingly, at our last orchid meeting there was a plant pathologist and he exclaimed that behind leaf spotting, rot etc... he almost always found that the plants had a magnesium deficiency. Perhaps you should be misting your plants with a Mg solution? Or working some Mg carbonate into the substrate?

Excess K causes the plant to reduce Mg uptake. Adding more Mg (via epsom salts) can help some, but it is fighting an uphill battle if you don't reduce K.

Secondarily Mg should not exceed Ca chronically, and can cause another set of problems.

So if you don't reduce K, then try some judicious use of a Cal/Mag supplement rather than straight Epsom salt. But I would avoid the "adding to compensate for antagonism spiral". Eventually you just hit the TDS wall.

 

[TyroneGenade]

Yes, Rick. You are quite right. I maintain planted aquariums with high light and CO2 and deficiencies develop very often. The impulse is to add to make up for the deficiency but then you get a news set of problems... I've learnt to rather step back and let the system reach a "balance" by itself while correcting my overall fertilizer schedule. So, now when I dose with anything I make sure I dose in proportion of other nutrients. If the dose doesn't work, then I change the proportion rather than supplement.

I am trying this approach with the orchids as well. When I fertilize with the Seagrow I add Mg/Ca into the solution at the MSU concentrations. So far this is working well. Growths do look better. Time will tell if I am getting accumulation problems. I have also repotted into a different substrate: plain sandstone gravel for the Paphs and many others with some leaf litter worked in for moisture retention and fertilizer. I had done some experiments with Complex Paphs previously, potting them in gravel and leaf litter, and this worked well. I got both good root growth and plant growth (but these were not fertilized in any way other than leaf litter). Time will tell if it is working.

 

[Trithor]

That Seagrow stuff is yuck! There are even bits of decomposed fish skeletons in it. Are you sure this is not the source of your ongoing problem.
I have had 50kg of 'K-lite' mixed up by a big fertilizer company, I am going to package and distribute it through the Orchid Council at cost if you are interested. I am sure it will need a bit of tweeking, but I am confident that I will have it sorted soon.

 

[TyroneGenade]

I only started using Seagrow after the epidemic and it quickly brought plants back into health and got them growing... But I am interested in the K-lite...

tt4n

 

[Trithor]

I only started using Seagrow after the epidemic and it quickly brought plants back into health and got them growing... But I am interested in the K-lite...

tt4n

Tyrone,
I am collecting the first batch of fertilizer tomorrow, as well as mag nitrate and calcium nitrate as separate components, will keep you updated. I am not sure how homogenous it will be, but I am excited.