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Orchidman

false scale on myrmecodia tuberosa

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ūüźú¬†I got a Myrmecodia¬†tuberosa seedling a few months ago (2 leaves , cadex 2 cm in diameter, tiny white spots on the leaves), put it in my greenhouse and it did not progress No new leaves , cadex did not grow. I mainly grow orchids and these spots did not look like any scale I have ever seen.¬†I put it in a terrarium and it grew¬†two new leaves¬†right away but produced MANY crystal-like /gelatinous looking things on the lower surface of the old leaves( enough to totally cover the leaf). The friend I got it from says this is false scale , not anything to worry about and a sign it likes the new conditions. Can anyone comment on false scale? Does this sound like it and¬†¬†if this as an actual a real thing?

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One of the first ant-plants I bought on eBay, back in 2000, arrived with what looked like scale on the undersides of the leaves.  The seller assured me it was not scale and encouraged me to look at it with a microscope.  Sure enough, they were corky scar tissue that sure looked like scale, but all the scraping of them that I did provided no evidence of living scale insects.  I have never heard the phrase "false scale" used for this until this year, 2018.  I would like to know where that phrase started?!

The most common explanation I have seen over the last 18 years is that the corky scar tissue I described above is the result of wild fluctuations of humidity coupled with excess water available at the roots causing guard cells on the stomata in the epidermis of the leaves  to burst and be replaced by corky scar tissue.  (for more explanation and photos see the two topics at the bottom of this "Diseases and other Problems" page called "White spots on my ant-plant" and "Leaf scars").  More information about this Oedema (edema) and Intumescences can be found in this fact sheet from the University of Massachusetts:  https://ag.umass.edu/greenhouse-floriculture/fact-sheets/oedema-intumescences.  It concerns Geraniums and also talks about other crops effected by edema.  Obviously there is not material written directly about ant-plants and these edema issues as ant-plants are not a multi-million or billion dollar industry like Geraniums and sweet potatoes.

Much of the research on edema issues comes out to the University of Kansas and some of it is casting doubt on on the above explanation for certain crops. (this is mentioned in the U. Mass article cited above)

A second explanation for the scaring and corky growths is damage from microscopic eriophyid/gall mites.  See and read the Topic two below this one:  "Help, problems with M. armata" for more information on this.

Finally let me point out some information specifically about Myrmecodias, Humidity and Intumescences.  It is in Chapter 5 of this historic book "Manual of Plant Diseases" from 1922.  The Myrmecodia information begins on page 437, but the way it is written will probably require reading more of the chapter to get the full meaning of it.  I want to thank a personal contact for leading me to this resource.  I hope he will join us on this forum soon and contribute directly to this topic.

 

 

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Thank you for your thoughts on this I am somewhat reassured and have put the plant back in the terrarium-like enclosure that it developed the issue in as it seems to be happy in that it grew the 2 new leaves. I had rubbed of and washed the undersides of the leaves right away and so no longer have the material to look at under a magnifying lens but if it occurs again I will not freakout so quickly and will look at it more closely and perhaps take a close-up picture. Because of the rather large orchid collection I have I was of course VERY concerned if it was a pest as treating the entire greenhouse for scale is an onerous task and one I like to avoid.

Thanks again for you reply

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Do these liquid filled "blisters" fit the description? I also have more images to make observations from with various types of corking. The ants that were roaming this Myrmecodia were chewing off the blisters and had to be road blocked to keep the blisters intact to photograph them. I coated the leaf petiole with petroleum jelly to barricade them. This worked, though I didn't know ants could jump to the leaf and I had to eliminate launch points. 

To determine if the blisters developed symmetrically on the back of the leaf, two images were taken frontlight and backlight respectively.

Over time the blisters dehydrated leaving a spot with a wrinkled epidermis. More blisters formed overlapping previous blister sites.

 

 

 

 

 

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pixlr.jpg

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Hi Philpatrick,  Welcome to the forum.  These are some fantastic observations and great photos.  I know a lot of us here are not familiar with the technology you are using so I hope you will indulge us with answers to the questions that will surely come.   Including right now from me!.....laughing....

What kind of microscope are you using please.  I don't think this kind of magnification comes on a dissecting microscope?   I know it would be very useful to us if you could indicate the magnification for each photograph next to it.

How do you know the clear sacs are water filled  -  did you see liquid rush out when the ants bite the blisters?  You say the ants were "chewing off the blisters"  They were actually eating or carrying away the clear (epidermis I assume) that was the cover of the blisters?  Do you think the ants were drinking or collecting the fluid in the blisters?

A few of the blisters seem to have thicker, slightly brownish walls.  Can you say that you think this is cork forming?  Or perhaps some artifact of the way some blisters photograph?

Are you confident (given the magnification you are using and the number of blisters you looked at) that there are no small mites or other vermin in the blisters that could be causing them?

And finally on the last two photos:  Am I correct that the top, darker green photo, is the top of the leaf being lit from above and the bottom yellower photo is still the top of the leaf but with no light from the top and only light from below?   I need some help here, what have these two photos shown you, I do not know how to interpret what I am seeing.

Well, I though that was all the help I needed here but after a half hour at this only now do my old eyes see some very clear, flatter looking circles on the photos!  Are these the blisters just forming and all the other ones I have been looking at have been compromised by the ants?

Sorry to ask so many questions - I may force you to write a book here......laughing.....

Seriously, thank you very much !!!

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These pictures do look very much like the issue with the seedling I originally brought up this issue about. As a follow up , when I returned the plant to the terrarium after washing the crystals off the leaves, the crystals again are forming on the bottom of the same (now older leaves). The newer two leaves are now larger than the original two leaves so the plants certainly seems happier than it was in the greenhouse. The two new leaves do not yet have these crystals forming on them. If it were due to any insect involvement you would expect it to occur on the new softer tissue of the new leaves not reoccurring on the older more hardened off tissue of the old leaves. Probably not due to insects!?

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I did not record any magnification data and I will start to post that information. The microscope was a zoom stereo trinocular dissecting microscope on an articulating arm. The photoport is coupled with a camera body and a tethered flash gun is used for lighting. The articulating arm combined with a turn table makes it easy to navigate around to scope the plant. I will try to include measurements and use a microscope slide rule since the images have been resized and cropped.

I took some pictures of the fluid before and after evaporation (1). I am not sure about composition. No fluid rushed out. I opened another "blister" with a hypodermic needle (2), the fluid inside quickly evaporates and large cell walls can be seen. 

(1)pixlr.thumb.jpg.a1276ce461b65ed59a42d03fea8a94bd.jpg

(2)pixlr_20180725223157899.thumb.jpg.1b4f844cae466b475af6e37fce1fc569.jpg

 

When the ants explored them with their antennae It reminded me of how ants zone in on extrafloral nectaries of some Nepenthes. 

These are thicker areas on the undersides of the leaves (3) and (4). My guess is the thicker areas are formed when the process repeats on the same site or proximal, overlapping and creating a thicker layer. If it is cork tissue, I am working on images to visualize the suberin if present.

(3)_MG_1914-1.thumb.jpg.d9ebeac440b83ea8d547ef363e83b585.jpg

(4)_MG_1915-1.thumb.jpg.f5cf50c52933f0acfe473030aa1c20f9.jpg

Yes Frank you are correct, the top darker green photo is the flash illuminating the top of the leaf with reflected light. The lighter yellow photo is the flash transmitting light through the leaf from behind. I took these pictures as an easy way to see if the blisters were symetrical on front as well as back. The dark shadows on the lighter image are mainly cast from the growths on the backside. The blisters can only be seen as an outline.

Yes,  the newly formed blisters are crystal clear.

The plant is in a terrarium with high humidity.

I had a question Orchidman, are the crystals on the top side of the leaf as well as the underside?

 

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These pictures do look very much like the issue with the seedling I originally brought up this issue about. As a follow up , when I returned the plant to the terrarium after washing the crystals off the leaves, the crystals again are forming on the bottom of the same (now older leaves). The newer two leaves are now larger than the original two leaves so the plants certainly seems happier than it was in the greenhouse. The two new leaves do not yet have these crystals forming on them. If it were due to any insect involvement you would expect it to occur on the new softer tissue of the new leaves not reoccurring on the older more hardened off tissue of the old leaves. Probably not due to insects!?

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The crystals only appear on the undersides of the leaves and as yet not at all on the new leaves. With the information here I am leaning to think the environmental change from the humidity changing from a varying 40% to 75 % in the greenhouse, depending on the time of day, to a constant 90% in the terrarium being the cause since the new leaves grew in this higher humidity and the older leaves growing at the lower humidity and then being moved to the new environment.

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