Problem: pest?

[macdafydd]

A few of my cacti are showing what seems to be abnormal growth. This "growth" is always accompanied by a white substance, rather woolly, but different to the cotton that surrounds the "cochinillas de algodón" (I think that's mealybug in English) that attack bougainvillaea in this area. I have tried scraping the growth to see if I can find any creature lurking within, but have found nothing obvious. The final photo below shows a red "something" that I uncovered, though the photo is in no way good enough to perform any identification; there was, in any case, no obvious movement. As can be seen in one of the photos, one cactus can be attacked, while its close neighbours, even of the same type, remain unaffected.

Can anyone tell me what is wrong and what I can do to remedy the problem?

[DaveW]

Just looks as if the tip has gone monstrose Macdafydd. You often do get the woolly growth initially with that type of fasciation. It is often cut off when large enough and continues to grow into a monstrose plant as in Cereus peruvianus monstrosus in the link below:-

http://www.cactusmuseum.com/oplant.asp? ... 025&PgNo=1

Cactus seem to be more prone to monstrose or cristate growth than most plants.

http://www.tucson-gardener.com/graphics ... ested.html

It can be genetic or even caused initially by insect damage, anything that upsets the growing point.

http://www.cssainc.org/index.php?Itemid ... &task=view

DaveW

[macdafydd]

Thank you, DaveW, for the somewhat comforting information. Certainly the Cereus in the first link looks remarkably like the cacti that have lost their "wooliness" already. Hope that's all it is!

[Aiko]

A few of my cacti are showing what seems to be abnormal growth. This "growth" is always accompanied by a white substance, rather woolly,

I have noticed the same with my Euphorbia horrida and Euphorbia schoenlandii, in the top. It accompanies my E. horrida when it is in bloom.

It is not woolly, but more flaky. Or crusty and looks a bit like dried up white sap. I don't think it is some sort of fungus or bug. But what it is, I don't know...

[IanW]

Depending on the species it could be growing a cephalium, but I don't think that's the case here, and it doesn't look like a cephalium bearing species.

[macdafydd]

It is not woolly, but more flaky. Or crusty and looks a bit like dried up white sap. I don't think it is some sort of fungus or bug.

Yes, that's a good description, "dried up whie sap", that's just it. I hope it isn't a pest and DaveW's suggestion gives me hope.

[macdafydd]

Depending on the species it could be growing a cephalium, but I don't think that's the case here, and it doesn't look like a cephalium bearing species.

No, definitely not a cephalium.

[Mal H]

Maybe it is a pest.

I saw this quite a lot in Lanzarote while on holiday this year, and saw several branching columnars that had these white masses on every growth point and the terminal growth points became a mass of small heads.

The only conclusion I could come to was that since Lanzarote still has the world's largest cochineal farming industry (supposedly) these were infestations. I do not have any photos of these particular columnars but you can see the effect on the Echinopsis in the first photo. The masses also grew in the split of the columnar below and had some of those red flecks you unearthed. The last photo shows the cochineal farm - unfortunately the renowned Jardin de Cactus is sited right in the midst of the fields of manky opuntias and when I visited it in June, many cacti in the Jardin de Cactus were infested and showed this terminal fluff and subsequent multi-growth points as on the Echinopsis.

[Mal H]

[Mal H]