cactus grubs

[Heretic]

I have recently aquired some trich specimens from a commercial ethno vendor [ NOT SAB ] . One of the cuts has black discolouration on its skin that appears fungal : inside it there appears to be some sort of grubs that I suspect may be cactoblastis larvae . Wondering if in fact cactoblastis will go for trichs and other species apart from prickly pear which they control well . If so , are these insects capable of devastating cacti collections , and capable of hitting lophs ? . I have cut out as much of the damage as possible , but am now left with a few small mutilated bits that I suspect I ought to get rid of rather than risking my other specimens . A commercial nursery that once employed me used to regularly spray their stock with a dimethoate [ Rogor ] / chlorpyrifos mix to control pests , but this is way too toxic for me to consider . Any ideas ? Apart from termites I have had very few problems with cacti pests in the past , nevertheless I am very concerned . Wondering if these larvae might have a local predator , rather than resorting to sistemic poison to eliminate them if encountered in future . [ BTW - I am gobsmacked that the vendor did not spot the blatant problem before sending , or perhaps they dont care ? In hindsight , I should have complained and returned the item , but I had mutilated it before thinking of this ] . any advice and suggestions are indeed appreciated , Tom .

[mutant]

its common, usually not leathal . search for 'black rot'. no cure

[Sir Jeans]

its common, usually not leathal . search for 'black rot'. no cure

 

I thought that black rot was not associated with insect activity.

The few times I have cut into a weeping black spot on a trich, I have never found any evidence of insects.

MajorTom, are you absolutely sure there were insects inside? A photo might help some of the more expereinced members help you out.

[Bread Filter]

I recently bought some "Achuma" cuttings from a guy on ebay. The cuttings arrived fully spined sitting on top of each other in a box with NO packaging. Obviously the spines gouged deep holes all through every cutting which have now turned black.

Any chance this is the same problem?

[tripsis]

Rot is separate to insect damage, but insects can lead to rot creating wounds which leads to infection.

I recently had a few grubs attacking the tips of my cacti. One resulted in a patch of rot, but I let it heal itself rather than cutting it out. Generally speaking, these grubs are not much of a problem and looking at your plants regularly is sufficient to control them. I've only ever had a few a year. Looking at what Cactoblastis larvae look like, I'd say the ones I have had are different. Whatever they are, they do burrow into the flesh and cause a fair bit of damage for their size. I wouldn't worry about them overly.

[Fluss]

I have found that dehydrating the cacti halts the devil himself when he creeps on my poles

[Heretic]

Thanks guys . Sorry , I dont have a camera to show you what has occurred . The damage is a black spot on the skin , and what appears to be black ' streaking ' on the outside from base to tip . Beneath the spots , which I thought were stings is rot inside the flesh . After gouging it out hard to tell what it actually is . I did not think of the black rot fungus because there has not been rain in my area for several months , but I dont know if this is the case where the cactus came from . I actually have not experienced much black rot on trichs where I live , even in wet seasons . They live in pots outside on a balcony all year happily without problems at all . My main concern is contamination to other cacti . In the past the only real damage has been yellowing from too much sun which I have no control of .

[Sir Jeans]

I think its unlikely you have anything at all to worry about. All my bridgesiis have the same thing, as do most other peoples from what I gather. Seems like a fairly benign thing that generally doesn't harm the plant or spread. But then again, its hard (at least for me) to be sure without seeing a photo. And yeah, are you sure there were insects inside? If so what did they look like?

[mutant]

this 'black rot' thing, which is actually a bacteria rather than rot, it seems, appears to live in the clone. Once it has it you cannot cure it, but it doesn't seem to spread and it doesnt seem to normally kill a plant.

There are ways to minimize the damage, that is minimise stress factors , including cutting , propagating, extreme wetness, surface damage.

each clone you will produce of the infected plant will have it.

but dont worry

EDITED BY MODERATOR! NO DISCUSSION ABOUT POTENCY AND INGESTION!

Edited November 27, 2011 by Evil Genius

[zelly]

I had a tricho that developed some sort of internal rot that extended upwards a good meter. There were no perforations of any kind to the exterior, just this internal rot. I found it when the column snapped over one day. My solution was to dig the plant up, roots & all, & toss it.

according to my theory all the 'best' clones in the world scene has it,

I think your theory is poppycock.

[tripsis]

Interesting you say that zelly, I have one presently which appears to have rot under the skin, but no obvious sign of external damage. Been watching it over the last few days wondering what it will do, whether it will spread and whether I'll have to cut it.

Edit: on closer inspection, it seems then are several pin prick type perforations on the epidermis. I suppose they are the site of infection.

Edited November 26, 2011 by tripsis

[CβL]

I have checked over 50 clones, and only the ones that came from abusive homes have black mould (not rot). That amounted to about 1 clone from memory.

I somehow don't think that 98% of my plants are average.

[Heretic]

I guess it is just the apparently common black infection , whatever it may be . I jumped to a grub conclusion because it appears to originate from spots on the skin , but is worse internally - sort of like an apple with a grub inside . I live in QLD and have been told that authorities still maintain the prickly pear control programme , and that the bugs can hit other genus besides opuntias . Whatever it is , I think I ought to toss the infected one . Many thanks for the opinions .

[mutant]

according to my theory all the 'best' clones in the world scene has it,

I think your theory is poppycock.

poppycock? what the heck is this?

apparently

two of the most famous ozzie clones, eileen, psychoo, got it.

EDITED BY MODERATOR! NO DISCUSSION ABOUT POTENCY AND INGESTION!

Edited November 27, 2011 by Evil Genius

[GoOnThen]

I had this for the first time last year only on bridgesii and only on about five plants

These are some photos taken last year before the welts started weeping

They now have scaring where the welts were but otherwise they are healthy

The other thing of note is the welts are all on the same north east side of the plants

Cheers

Got

[mutant]

I continued some experiment of mine.

the subject was a standard bridgesii, black rot positive,

I took a scarred piece, about 15 cm tall, mid section and sliced it numerous times vertically to see what was happening under the scars.

Apparently there is a fatter green flesh area underneath the scars and less often there are random green-fleshed 'tunnels' near the scars

EDITED BY MODERATOR!!! NO DISCUSSION ABOUT POTENCY AND INGESTION!

Edited November 27, 2011 by Evil Genius

[tedzr]

I've found this happens on most of my trichs (only 10-15 plants), especially when I take a cutting. It usually appears near the cut site but sometimes shows further up the stems. I just keep it dry and it normally goes away in a couple of weeks, leaving some scarring at the site.

A few years back when I first started growing cacti however, I noticed some at the base of a very nice TBM, about 10" high with many branches that I picked up for a steal. Being a greenhorn, I got alarmed thinking, 'omg I hope this doesn't spread - I must DO something about it' and cut the black chunk out with a clean blade and treated the plant with sulphur and fungicide. Subsequently over the course of the next few days the cactus turned to little bags of mush. I now have the literal shell of a TBM sitting in a laundry somewhere.

With regards to the 'black dots' from spines of branches penetrating the flesh of other branches, my advice would be to just let it dry out as much as possible and don't really worry about it. They stay around for a while but don't seem to cause serious damage to the plant. Apparently you can use cactus spines as an adhesive in grafting without detriment however I have not tried this.

Regards.