Advice please: disease or corking?

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SpikyMike
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Advice please: disease or corking?

Post by SpikyMike » Sat Nov 17, 2018 4:25 pm

Hi. I have a small Gymnocalycium ladefense. It has a brown discolouration appearing circumferentially around the base of the plant. Looks healthy otherwise. I’ve not seen any mealy bugs or red spiders. Not sure if it is disease (possibly fungal? Some sort of rust fungus?). or if is merely natural corking. Should I be isolating? Treating?
Advice gratefully received!

Thanks. Mike
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Mike Walton
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habanerocat
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Re: Advice please: disease or corking?

Post by habanerocat » Sat Nov 17, 2018 5:45 pm

I certainly would be worried about Red Spider Mites. The are too small to see.
I'd isolate and spray it asap.
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Ali Baba
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Re: Advice please: disease or corking?

Post by Ali Baba » Sat Nov 17, 2018 6:28 pm

The scarring looks suspicious for flat mites (brevipalpus russulus) which cause a disproportionate amount of damage relative to their numbers, and hence are very tricky to spot. They are also smaller than red spider mites. I would have it out of its pot and have a good look at the base of the plant with a magnifying glass. You might see the red egg cases even if you don’t see the adults.
If you find evidence I would dip the whole plant in a plant oil based insecticide and leave it to dry in a warm place.
Dipping is much more effective than spraying as they lurk in crevices, and plant oil treatments are more effective than acaricides as resistance is less of a problem.
Isolate and repeat in a week or so to kill any escapees. You will need to have a good look at any plants in close proximity too.
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SpikyMike
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Re: Advice please: disease or corking?

Post by SpikyMike » Sat Nov 17, 2018 6:58 pm

Thanks Ali! You mention ‘plant oil based incecticide’. Can you elaborate? I’ve heard of something called ‘neem oil’ (for mealy bug). Is this what you mean? Or something else? And where can one buy it in UK? Thanks mate!
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Re: Advice please: disease or corking?

Post by MikeT » Sat Nov 17, 2018 7:35 pm

The position of the damage low down at the base of the stem is typical for natural 'corking'. RSM tend to go for the softest tissue, the newest growth in the top of the plant. As far as I can see from the photo, the newest growth looks fine - in which case I don't think you have anything to worry about.
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Ali Baba
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Re: Advice please: disease or corking?

Post by Ali Baba » Sat Nov 17, 2018 8:14 pm

It could be corking but the colour is a bit odd, in my experience natural corking is usually a pale buff colour. Flat mites often feed low down at first and can be missed, so I’d have a look to be on the safe side. Hopefully Mike is correct!😀
Oil based insecticides are probably withdrawn now in the uk although I still have a few bottles left (don’t tell anyone).
There are plenty of recipes on the internet though, just an emulsifier like soft soap, rapeseed oil and water. The oil emulsion blocks the breathing pores of the bugs and they die
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Re: Advice please: disease or corking?

Post by Peter » Sat Nov 17, 2018 8:25 pm

I just hope that there's some decent roots and not a mushy mesh due to over watering.
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Re: Advice please: disease or corking?

Post by gerald » Sat Nov 17, 2018 8:32 pm

Mike's right in that most mites tend to feed on the new, tender growth at the meristem. But this does look like mite damage, even though it's near the base.

Despite that, you can't rule out mites, so I would follow the above advice ie quarantine and treat as if it were mites. Throw the soil and pot away. Neem oil should do the trick.
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Re: Advice please: disease or corking?

Post by habanerocat » Sun Nov 18, 2018 10:50 am

The offsets are too young to have corking. It has to be some sort of an imposter.
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Re: Advice please: disease or corking?

Post by iann » Sun Nov 18, 2018 9:07 pm

Flat mites prefer the base of most cacti, and they prefer the shady side also. They don't like too much exposure. Damage tends to be mottled and will appear rapidly, usually a lot of damage by the time you notice anything. You'll need a lens to spot them, half the size of spider mites at most, always orangey-red, a similar colour to plastic plant pots but somewhat translucent. They can be especially dangerous over winter when they enjoy the humidity, lack of sun, and lack of ventilation. They will grow slower at low temperatures, but 4-6 months without checking over your plants gives them plenty of time to wreak havoc.
Cheshire, UK
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