Grey-ing opuntia

Trouble shoot problems you are having with your cactus.
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dvdmsy
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Grey-ing opuntia

Post by dvdmsy »

Heya -

Is this de-coloration anything to worry about?

Thanks in advance.
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cgillett5
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Re: Grey-ing opuntia

Post by cgillett5 »

I'm not an expert, but I'd say something is wrong. Go thru the pest article. It's at least a spot to start.
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hegar
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Re: Grey-ing opuntia

Post by hegar »

That looks like a fungal infection to me. I assume, that the other side of the cladode (pad) also does have these lesions.
The concentric growth pattern is typical of some fungi. Also, there seem to be little spheres visible in some of these lesions.
Those most likely are fungal fruit bodies. What color do these bumps have and what shape?
If they are slit-like in appearance or cushion shaped and have a yellowish color, then most likely you do have a Colletotrichum sp. fungus attacking your plant.

Harald
dvdmsy
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Re: Grey-ing opuntia

Post by dvdmsy »

Heya, thanks for your response Harald and cgillett5. Yeah, the plant has the fungus on both sides, but one is much worse than the other. My only guess is that this might be because one side received much more light during the indoor winter months than the other. The bumps are yellowish and circular. I've treated it with acephate 97UP.
dvdmsy
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Re: Grey-ing opuntia

Post by dvdmsy »

Any advice on the best way to treat this?
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hegar
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Re: Grey-ing opuntia

Post by hegar »

In order to do an effective treatment, you have to know what causes the problem. If it is indeed a fungus, you need to apply an fungicide. However, it could be a bacterial infection. Then a fungicide treatment would not do any good.
In all these years that I have grown cacti, including a good number of prickly pear cacti, I have not seen this kind of problem. Opuntia spp. are "low cost cacti" and it may actually be best, to discard this plant including soil and perhaps even the pot and get yourself another one. With an infection this bad, treatment may not be successful anyway.
If you were here, I could examine your plant, employing a microscope. Also, you could literally take bucket-fulls of various Opuntia spp. home for free.
With a magnifying glass, you could take a close look at the largest of those cactus lesions and then, based on what you see, try to figure out, what kind of pathogen could be responsible for those spots. There is information available on-line, including some good descriptions of fungal pathogens infecting cacti. I did download this a long time ago, but do not know exactly, where I filed it. The source of that material was the Texas A&M University, College Station, Texas, if I recall it correctly.

Harald
dvdmsy
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Re: Grey-ing opuntia

Post by dvdmsy »

Thanks, Harald. Yeah, I fear you're right about needing to discard it and one other that has similar markings. Of course, I have an emotional attachment to this plant, but if there's a chance that it infects my other plants, then it's not worth keeping it. If there's no harm in letting it go through the summer, then I might do that.
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hegar
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Re: Grey-ing opuntia

Post by hegar »

You could isolate this plant from other cacti and observe what happens. Prickly pear cacti are usually very tough, but with those lesions covering almost the whole plant body I do not see a very good chance of recovery for your plant.
Even if the disease does not consume the interior of your cactus, I think, that it will be having a great problem with the process of photosynthesis, because the pathogen takes up almost all the surface area.
It would be nice, if there was at least a decent-sized piece without any lesion. Then you could go ahead, give that part a fungal treatment, i.e. if this is indeed a fungus, and then try to root it. But with a plant of low monetary value, I would not even consider this. The treatment would exceed the cost of a new cactus pad.
Do you have anything like a cactus club in your area? If so, I am sure, that any member who does grow Opuntia spp. will be more than happy to give you a cladode or even several of them.

Harald
dvdmsy
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Re: Grey-ing opuntia

Post by dvdmsy »

It's not really a monetary issue. When I travel, I bring home a plant as a souvenir, a connection to the place (this is of course a common practice across human history, from Ancient Rome to Imperial India and beyond). So that's the only value that the plant has -- that and the time it's taken to root it, grow it.
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hegar
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Re: Grey-ing opuntia

Post by hegar »

If you brought this cactus pad from a foreign country without declaring it to the Customs and Border Protection Service officials, you did something rather risky and potentially quite expensive. Most plants do require a certificate of health (phytosanitary certificate), some are outright prohibited, because of a quarantine, and others, including cacti, require CITES documentation in order to be permitted entry into the U.S.A.
During my time "in the trenches", we could assess spot fines, that needed to be payed immediately ranging from $25 to $100.00. The higher amount was charged, if the plant or plant product was concealed. Now the fines are already at $300.00. I am not sure, if something that was neither declared nor concealed can result in a $300.00 fine, or if this is the upper limit for a concealed item.
At airports in this country, trained dogs are on duty, which can indicate, if things of agricultural importance are present, even in closed luggage and containers. Also, you probably know, that hand-carried luggage is usually x-rayed and oftentimes opened by TSA agents.
So, bringing a souvenir from the animal or plant kingdom could become a very costly decision. I personally would not take that risk.

I do understand, that things purchased or obtained for free in another country do have a sentimental value based on the association with the place visited. However, it would be wise, not to bring anything that could result in substantial fines. In some countries for example, it may be totally legal to own ivory items made of elephant tusks. Bringing them into this country though is illegal and will cause anybody who is detected with that item a major headache i.e. delays, fines, or even a jail term, if the quantity is high enough.

Harald
dvdmsy
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Re: Grey-ing opuntia

Post by dvdmsy »

The cactus is from California...
A. Dean Stock
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Re: Grey-ing opuntia

Post by A. Dean Stock »

To a "Texan", California probably qualifies as a foreign country !!! I know, I lived in Texas for some time and indeed it takes a day or two to drive out of it. I agree that the infection in this Opuntia is very odd. I've never seen anything quite like that except for certain virus diseases of cactus. I fully agree with Harald, dump the cactus and get another one (or more).
Dean
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hegar
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Re: Grey-ing opuntia

Post by hegar »

Hello dvdmsy,
what "threw me off" was your statement about travel to ancient Rome and imperial India. So I had the feeling, that the prickly pear pad was actually imported into the United States of America, although I wondered, why someone would bring in this kind of cactus from a foreign country.
When I used to inspect vehicles and pedestrian luggage of people coming from Mexico, finding Opuntia sp. cladodes and fruits was a very common thing. We did allow the fruit and new pads for consumption into the country, but the more mature pads were seized and destroyed.
Dean is correct. Texas is a huge state, second to Alaska in size. With my prior home country in Europe, this state covers the area of several small countries in Europe. I would always tell students, that the state of New Mexico is about equal in size to the country of then West Germany!

I am glad, that you took this prickly pear pad from somewhere in California. The only violation you could have made is, if you cut a cladode off a plant growing in a State or National Park. I do know of a case, where a couple from Europe collected cactus seed inside a State Park and the U.S. Fish and Wildlife Service agent wants to prosecute this case in court!
I do not want anybody to get into trouble with the law and that is the reason I am warning people here on the forum.

Harald
dvdmsy
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Re: Grey-ing opuntia

Post by dvdmsy »

Thanks Dean and Harald for your replies. I think the humidity of the Northeast (I live a block from the East River which, as you might know, is not a river at all but a tidal strait and therefore salt water) might have something to do with my West Coast plants having a difficult time adapting to their home on an NYC fire escape. We have only one native opuntia (humifusa), and as much as I appreciate it, I like to diversify. Trial and error to be sure.
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