Spots and Speciosum . . .



© Gerry Walsh



Leopards have them, dendrobium beetles have them, I had them when I was a teenager. My long departed Aunty Maude had a huge number of spots of endless colouration, God rest her soul. My father is 99 years old and has more spots then a plate full of fairy bread. And speciosums get spots too. And the older a speciosum gets then the more spots it gets on its leaves. Just like with my old man, they are unavoidable on our favourite native orchid.

Spots are just a part of speciosums growing old. Part of their life cycle if you like. No plant lives for ever and as they age, spots will start to invade. They can scare the hell out of a chronic orchid grower when they appear. New chum growers are even worse. If they see spots they assume that a vegetative version of Ebola must be lurking about. They assume that the cause is virus.  IT MUST BE VIRUS! is the screech that often echoes through the bush houses of suburbia.

It can be of course but with speciosums it rarely is. I am not going to discuss virus in speciosums here at the moment. To be honest, I know nearly nothing about it. I have seen plants from time to time that I keep clear of, mostly at shows when judging. Occasional plants have been removed from a show bench if a panel of judges thinks a plant has the pox or whatever. I do not grow non-native species at all. However, it seems that exotic growers are in a continual state of the jitters as so many genera seem susceptible to some virus or other.

BACK TO THE TASK AT HAND . . .

As a new bulb hardens off it can look, in my eyes, as great as an opening raceme. If all is well there will be four or five perfectly formed leaves with snow white sheaths around big fat bulbs loaded with flowering eyes. As the years go on the eyes give up their treasure and new bulbs replace the old ones spent. But the old ones can hang on for a long time. I have plants with markings made with a texta pen 14 years before the present. Eventually the leaves will wither and fall.

Spots and stains and holes and marks of all kinds take over and disfigure the leaves along the way. It cannot be avoided and it is something that just has to be accepted.

If you get spots on new bulbs and leaves there can be many reasons for it. Absolutely any insect at all can be responsible. There is no point in making a list of likely contenders. One thing to be remembered is this. If a bug makes a nick in an immature bulb, when that bulb is mature the nick will be much bigger. Good reason to keep out an eye for any troubling critters at the tender stage. I do not need to give a lecture on watching out for scale and aphids etc. Everyone knows the deal with those pests. Just keep all this in your mind and stay alert. You cannot get lazy about diligence!

As a general rule I can make the following observation. The tropical varieties of speciosum, when grown in colder climates like Sydney, and no doubt Melbourne, will always get more spots and marks and stains then the more temperate varieties from south of the Tropic of Capricorn. In Particular var. curvicaule and var. boreale will be the most affected. Var. pedunculatum does not seem to be as susceptible as the first two. Carnarvonense, Blackdownense and Capricornicum from  right on the Tropic line seem free of the scurge.

Curvicaule plants in my bush house can be recognised without looking at labels just by the spots and dags etc on the older leaves. Even from four or five metres away. Curvicaule is also more likely to get fine lichen coatings on the leaf surface. I don not let this worry me at all. I live with it. In the wild, curvicaule is the carrier of lots of leaf lichen. It seems that in the bush house this is replicated. So all these factors make my curvicaules look the least manicured plants of all the nine varieties – in my set up anyway.

IN SUMMARY . . .

Don not let spots worry you too much folks. They are a natural part of the life cycle of a speciosum. Or any living plant really. And if you happen to be the recipient of any of my rock lilies then you may have a spot or two on the older bulbs. If it is the younger, just matured growths which get spots and holes in them, then you better start an investigation quick smart. Something may be wrong. Once again the likely culprits will be insects and/or excessive watering or rain. In winter time in Sydney you should not be watering your larger established speciosums more than once a week. Even then, only in the mornings after the sun comes up. Never in the late afternoon at all, in winter at least.

Having said all this there are the hard core top notch growers who steal holy water from the local church just to water with. They play Armenian Folk Music to their plants and consult astrological charts before they will even venture into the bush house. Even they will end up with spots on the older growths eventually.

If you only have a few dozen speciosums then it may be quite possible to spray with this and that and keep spots at bay for another year. Or go to your herbalist and get an elixir made from Aardvark toenail extract to dab on a blemish. That might work as well. Personally, I have more to do in my life then worry about such things. Do not get morbid about your spots people . . . just like Aunty Maude and my father, you cannot avoid them. Do not let them rule your life.

My God, I think I see a pimple on my chin! Wait up, its just a skin cancer . . . PHEWWW!

In these pics above you will see the ugly scungy marks which often inflict the understide of speciosum leaves. It is most often seen on the older leaves. However, occasionally I get it on the leaves of bulbs that are not too old at all. And it can also be seen on the top of the leaf as well. A lot depends on the humidity in the your bush house.

At my old address, I built a second bush house with a solid opaque roof. This was done to keep me in control of everything. Rain was not going to wreck the blooms any more! And this very expensive pursuit did the trick all right. I had the best bloomings I have ever had. Then I up and moved house after only 3 spring times. Hmmmm.

What I did not count on was the drier humidity, so it would seem, caused an outbreak of these scungy marks that I had not ever experienced. Plants left in the shade cloth covered old bush house did not suffer at all and remained normal. I was completely dumbfounded and had not a clue what was happening in the new Hilton Bush House. Was it something terrible?

Not far from me lives Allan Merriman who has lived and breathed orchids for all of his life. His nursery is called Miriam Anne Orchids. He is the denizen of wisdom when it comes to orchid disease and condition. I went to see him with evidence in hand. He informed me to my great relief that my problem was  Cercospora dendrobii. I thought as much!!!

Never heard of it naturally. As usual Allan gave me his wisdom and told me it was easily controlled with a few simple precautions. He was firm that prevention is the best possible path to embark on. These are his instructions.

PART ONE:

1: Mix up a lime solution at 250 grams to 50 litres of water.

2: Leave overnight to settle out. Next day, do not stir it up. You only want the lime water. The residue is only chalk. It’s the water you need to spray.

3: So spray every leaf surface both upper and lower. DO ALL YOUR PLANTS. Not just the affected ones. REPEAT EVERY TWO MONTHS.

PART TWO;  Twice a year you must sprinkle hybrated lime powder over all the leaves. Leave for two days and then lightly spray off with a fine water mist.

PART TWO:

Use Ippon Fungicide at the rate of one gram per litre.

Separately mix up Mancozeb at 1.5 grams per litre. Mix this in a separate container to the Ippon. If you do not, you will get a sticky lumpy mess like gravy gone wrong and it will not work.

Measure out the required amount of water and add the Ippon and then the wetted down Mancozeb as well. Stir it like hell. Then spray it on every surface of every leaf and the bulbs as well. DO THIS FOUR TIMES A YEAR.

This is what Allen told me to do. And YES, it worked. Stopped the plague in its tracks. I have now reached an equilibrium with my speciosums where  Circospora dendrobii doesn’t seem to be an issue these days. So, naturally, like an idiot, I no longer do it. What with moving house and turning my world upside down 6 months ago, there was no time.

DO NOT DO WHAT I DO . .. DO WHAT ALLAN SAYS, SO IT IS WRITTEN. There you have it.

The upper and lower surface of the same leaf. It isn’t always obvious so be on your guard please.

Typical spotting on variety curvicaule.Tropical speciosums seem to get this far more  then temperate varieties. As discussed above. Lichen growth on curvicaule can also be a problem.