Diseased Cactus. Please help!

I've had this cactus for more than 10 years now, and in the past few months the top end surface of it started to develop this strange covering. Please see the attached photos for a better idea of what I'm talking about.

What exactly is causing this? Is there any way to save the plant?

Also, could anyone help me identify it?

Thanks!

 

it's probably fungul - you'll need to treat with a fungicide.

 

I'm not too sure that is fungal. I've had a few cacti over the years, and some of them have done that. Occasionally it was from too much direct sun. Don't get excited, some cacti have a hard time with too much sun at the hottest part of the day. Others did it without the above problem. I read about it, and as I recall the book said that if can happen naturally and called it something like 'corking'. Now I don't believe everything I read in books, or see on Google Image ;), but perhaps something other than fungal is going on here. Now, that said, that plant does not look happy, so a 'natural occurence' may be way off. Or I'm all wrong and the poor thing has a fungus.

 

I didn't think it was getting overexposed to sunlight since, as you can see from the photos, the blinds were always drawn. I'm not a gardening expert by a long shot, but the white stringy material growing at the top end of the plant does look like fungus (shown in second picture from the right). What I'd like to find out is whether or not the white stuff is related to the "corking" appearance spreading on the top half surface.

I guess I'll apply some fungicide just in case, and see how it goes. Do cacti require any special kind of fungicide? I have one that's used to treat roses and such.

Thanks again :)

 

i first thought of sunburn as well. that would normally only be on one side of the plant - not all around on every side. corking usually happens at the base, as far as i'm aware of.

the other thing about it being fungal is that there's that tiny branch growing at the top and that is still green even though the top part of the main part of the plant is discolored. if it were a burn, then the new growth would also be discolored.

also, i got in a couple new plants in the spring...looked nice and healthy - one even put out new growth after it rooted...the one that was already rooted never showed any new growth and, after about a month, both of them started to show the same look as the one pictured here - within a few days of each other, too.

i'd originally thought it was burn...and moved them back from the light. and then when it didn't get better, i thought the burn would be a permanant scar. i didn't think about fungal and didn't treat with fungicide.

in my case, it's definitely fungal - within another month of the initial showing both were completely covered and then i lost the one and the other is barely hanging on...and the fungus has spread to three other plants since :(

 

of the two that were the first to show signs of disease - one looks identical to yours and the other one has a whitish crusty coating like what is at the top of yours...what i have are two different species - another reason i didn't realize the problem was fungal...the one looks like a burn (like yours does) and the other one it was clear was fungal.

in over 30 years of having plants, i've never had any kind of issue other than mealy bugs. so, even though i knew about fungal infections, i'd never seen one - so i missed the opportunity to treat before it was too late for the one plant.

i can't remember the name of the stuff i got to treat...i'll post it later when i get home from work.

 

Couldn't hurt to try the appropriate fungicide, and then think about culture. Just reading your comment about the "blinds were always drawn"...

 

I am wondering if infact, you have or had a case of mealy bugs. The whitish stuff looks just like what they leave around when eradicated.

But I think what may be going on is meristem death. For some reason this plant is offsetting a new plant right at the tip. That usually only happens when the meristem or growing center dies. And mealie bugs can eat the meristem killing it. I have one cacti that is suffering with that problem right now.

 

Good call! Yesterday I picked off a tiny, white, oval-shaped insect from the new plant using a pair of forceps. At the time I didn't know what it was, so I just dismissed it. What I saw matched up with pictures of mealybugs I just googled up.

Is it too late to save the main stem? Is there any other way to control mealybugs other than using insecticides?

 

interesting!! i'd never have associated mealies with this!!! learn something new every day!!

i've definitely not got mealies though...hmm. guess i should go take another look, huh?

mealy bugs can be treated with q-tips dipped in rubbing alcohol - just touch the bugs with the wet q-tip and they'll die. if the infestation is bad, you can spray the r-a on. just don't do that in full sunlight and make sure to cover the soil with plastic to catch any that drips down. the r-a won't hurt the plant - it dries off before any damage can be done...you don't want it getting into the soil though as that will cause damage.

there are also mealy bugs that go underground and live on the roots. you may want to repot - remove all the soil, clean the pot well with bleach & hot water (and rinse very, very well to remove the bleach residue) or just get a new planter and then repot it.

 

Thanks joclyn! I'll give the rubbing alcohol a try.

EDIT: Another question: Do mealybugs burrow beneath the surface of plants? Other than the white waxy material and that one bug I picked off two days ago, there were no obvious signs of the bugs. There has to be more than one bug causing all this trouble...but where did all the others go?

 

yes, root mealies. if you don't see a lot of them and have severe damage, then the only answer (other than fungal; which may be a resulting issue due to the mealy damage reducing the plants health and making it susceptible to the fungus) would be the under-the-soil type of mealy bug.

repotting is definitely something that should be done!!

darn! i keep forgetting to get the name of the fungicide...

 

When you do the rubbing alcohol treatment, do keep the cactus out of the sun like mentioned, wait until it it dry, or the skin will turn white otherwise. Not good!

 

look real close, i wouldn't rule out thrips or spidermites

 

The plant is putting out a new shoot so the tip has stopped growing. Mealies and spidermite have beem mentioned.

Looks like the plant has either scale, a fungal problem (maybe a slow one) or some sort of "rash".
Some of my plants have devekoed rash from root mealies (damage root and then fungus can get into plant) or from too much sun/UV light. Insects (scale insect , regular mealies) might cause such a reaction in your plant. Find out the cause first. You may not require any fungicide or insecticide.

Good luck