Oxalis Control?

[DaveW]

I would be interested in the more chemically knowledgeable's opinion on this article "Weed Control in Greenhouses: How We Learned to Love Herbicides" a claimed method of killing Oxalis and whether cacti are in fact immune to Roundup? I have heard of similar systemic weed killers being applied to Oxalis leaves with an artists paint brush to hopefully kill the Oxalis but to avoid getting it on the cactus, but never by just spraying it around the plants themselves:-

http://www.tucsoncactus.org/pdf_files/May14.pdf" onclick="window.open(this.href);return false;

Obviously it would need to be sprayed on some cacti that did not matter as a trial, but Oxalis being such a pest it would be a godsend if it were safe. I used it on some Creeping Buttercup that spread everywhere in the garden that I had failed to eradicate by other means and it worked a treat.

[iann]

Immune no, but slow metabolism and a large volume compared to surface area offers some protection. Glyphosate requires an active metabolism to move within the plant, and interferes with the plant chemistry in such a way that it essentially poisons itself. Plants that aren't growing don't poison themselves. Because of this it is most effective on vigorous plants. You can even spray a Dandelion in winter and it is likely to survive. If you're lucky ... or unlucky?

[iann]

Not having stomata open during the day probably helps too.

[DaveW]

I was told years ago Ian somebody used to kill Oxalis around cacti by dabbing the leaves with Paraquat

"Paraquat is the trade name for N,N′-dimethyl-4,4′-bipyridinium dichloride, is the organic compound with the formula [(C5H4N)2]Cl2. It is classified as a viologen, a family of redox-active heterocycles of similar structure. This salt is one of the most widely used herbicides. It is quick-acting and non-selective, killing green plant tissue on contact. It is also toxic to human beings and animals. It is linked to development of Parkinson's disease."

It was banned in the UK in 2007 and I think the rest of the EU?

"Use of paraquat has been banned in 13 countries including Sweden, Denmark, Austria and Finland. Following the court decision Germany have also decided to suspend registration of paraquat containing pesticide products."

Therefore I was wondering if Roundup would work the same?

[cactushobbyman]

I use Round up around my outdoor cactus. Mostly in early spring to knock down the early growth. I do get some on the cactus and so far no death. I spray Round up on the Bermuda grass but my cactus beds is fairly clear of Bermuda. Never use it in the greenhouse.