The MGS Forum

Gardening in mediterranean climates => Pests and diseases => Topic started by: ezeiza on March 17, 2012, 12:06:52 AM

Title: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: ezeiza on March 17, 2012, 12:06:52 AM
If the stems are cylindrical it is Oxalis pes caprae.

South African oxalises are potential weeds in mediterranean climates. They  can be easily exterminated with glyphosate with the glove method explained before.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 17, 2012, 11:32:27 AM
In much of Greece the single Oxalis pes-caprae ("bermuda clover" or "bermuda buttercup") is widespread and completely out of control, carpeting open spaces and olive groves to the virtual exclusion of wild flowers that bloom at the same time. As Alberto says, glyphosate does eliminate it, but those who rely on non-chemical methods find it virtually impossible to exclude this pest from gardens in areas that are infested with it.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Cali on March 17, 2012, 12:08:08 PM
Alisdair, I am relatively lucky in that I don't have that much, and what I do have I've controled with weeding while the soil is still soft.  (One of my pet peeves is with peolple who exclaim how beautiful it looks as it swarms accross the land sweeping everything in its wake....)
Thank you Pamela, Jorund and ezeiza.
Cali
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: ezeiza on March 18, 2012, 01:28:01 PM
The problem is that with such terrible pests there is not much to think. And, glyphosate can be very useful and its impact lowest if used the properly. You are solving a highly artificial problem with a natural method and it simply does not work. Pulling the clump while the ground is wet and soft is excellent but how can this be done when hectares of them are involved. Spot treatment now, instead of plane fumigation later.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: anita on March 18, 2012, 01:52:51 PM
O. Pes-caprae is a menace in southern Australia too. In broadacres glyphosate is the only way to go. However it can be eliminated in smaller gardens by being persistent. When I moved to my current home 11 years ago the garden was yellow in late winter/spring. I now have a patch left in the lawn but the rest have been defeated by persistent hand weeding. There are two key things pull them up early so as to exhaust the bulbs then repeat as the plant regrows. And then repeat again. The other important thing is to burn or very deeply bury the pulled plants. If you leave them on the ground the uprooted plants will form bulbils and you will be back at square one. If you are diligent the yellow peril can be defeated. The first years here I literally pulled out wheel barrow loads. Then it was down to buckets. Now I'm chasing the last little plants hiding in the lawn using just a 2 litre icecream container. The remaining plants are so tiny their stems are threadlike but I can't let them live or they'll recolonise.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 18, 2012, 02:05:02 PM
 (http://[/url)
Dear Cali
I, too have this double oxalis in a few places and I love it. I do not pull it out like the single version. It does have a pretty red hue.  Do you have this oxalis problem in Greece as well ?? I spend hours pulling them out. I really do not know how to get rid of them. Someone from SoCal told me you should always CUT them off at ground level rather than pulling them as this starves the bulbs which then die. Have you heard this?  
Pamela, commenting on the red double-flowered version mentioned here (http://www.mgsforum.org/smf/index.php?topic=726) by Cali and others, raised the issue of how to deal with the invasive single version. As this can be such a pest, I think it's best to treat is as a separate problem, under Pests and Diseases.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: pamela on March 18, 2012, 06:20:45 PM
Dear ezeiza
Thank you for your ideas.  When you say 'spot treatment' , how do you go about that?

Its impossible for me to use glyphosate as my Oxalis is between shrubs, bulbs and other plants. 
That chemical would kill everything near to it. It's just too risky.

I was interested in how Anita has solved her problem.
Do you start pulling as soon as they appear?  I was told to wait for the flowers......
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: ezeiza on March 18, 2012, 11:47:13 PM
"Spot treatment" is very easy: prepare a 10-20% glyphosate solution in a plastic container (can be a half soda bottle, etc.). Now put on latex gloves. Dip the tip of your fingers (or that part of them that face the palm) in the glyphosate solution. Gently grab the plant you want to kill with your herbicide soaked palm/fingers and move your hand towards you. This motion actually paints it with the herbicide and the method is based in the principle that if you apply the herbicide on part of the plant the whole will be affected. Once you get the knack it is very simple and fast to paint many plants in a few hours and this will not affect neighboring plants (if you do not touch them!). One common mistake with glyphosate is to use doses so high that the tissues are actually burnt without the plants absorbing the herbicide. But, this has been mentioned before. Latex gloves must be discarded afterwards or well washed with warm soapy water.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: David Bracey on March 19, 2012, 09:34:21 AM
I use a small/large paintbrush depending on the size of the problem.  Add a squirt of washing up liquid which will help the "sticking" process.  The treated plants wilt quite rapidly, after 24 hours but the full effect will rake the best part of 2 weeks. A 10% solution is ample. .
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 19, 2012, 10:43:40 AM
Like David, we use a paintbrush too in areas where bermuda clover is invading planted areas, which does work well but is not quick. So I aim to try Alberto's glove method - much as I hate wearing latex gloves! (I'm hoping I can persuade Helena to do it instead as she's quite inured to them.)
Alberto's point about avoiding too high a concentration is important - counter-intuitive but true, that higher concentrations can actually be less effective.
If you have a good sprayer you can spray glyphosate very close to vulnerable plants without damaging them, so long as you keep the spray pressure as low as possible, and spray in cool calm conditions to avoid drift. Also, at least in my own experience glyphosate doesn't damage mature wood.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: JTh on March 19, 2012, 10:56:15 AM
I don't like to use these weed-killers, but the few times I have done so, I also preferred the spot treanment. I put a pair of cotton gloves on top of the latex gloves, they are more absorbent and there is less chance of accidental dripping on other plants.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: anita on March 19, 2012, 12:38:26 PM
I was interested in how Anita has solved her problem.
Do you start pulling as soon as they appear?  I was told to wait for the flowers......
Pamela, I start pulling them out as soon as they appear. I've found that by the time they flower they are already setting new corms. So I weed as soon as they are big enough to grasp. I've used JTh's method with cotton glove liners worn outside latex gloves and it is quick and effective but my garden had been near abandoned for five or more years and when the autumn rains came I had oxalis everywhere and it was risky to use the glove method amongst perennials. It's not the world's easiest solution as you have to repeat the weeding until the corms are exhausted.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: pamela on March 19, 2012, 03:54:10 PM
Well, this is all very fascinating.  I have never used weed killer in my garden in fact I don't have any on the property. But, possibly I might brave it and use glyphosate in these very controlled conditions. It could be an answer.  Two more questions:  Can I have a reliable brand name or several brand names please?.  Does the 'painting' of the leaves kill the corms/bulblets as well, meaning that plant won't come up next year?
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 19, 2012, 04:26:22 PM
In Europe as in the USA Monsanto, the original developer of this weedkiller, is still the main supplier of glyphosate, even though their patent expired some years ago. They supply it under the brand name Roundup; this includes a surfactant and spreading agent, which help in applying it.
If the glyphosate is applied to the leaves of a bermuda clover plant, all parts of the plant including the attached underground bulbils will die. But any detached bulbils which do not have any above-ground parts will survive (glyphosate is inactivated by contact with the soil).
Glyphosate is not a magic potion (in the UK some weeds of farmland such as willowherb have developed strains that are highly resistant to it, and the same has happened in the USA; there seems also to be some evidence that its use on the same spot year after year, as happens on many arable farms, may in the long run damage soil structure). But as weedkillers go it is remarkably non-toxic - one formulation is even authorised here in the UK for use on wetlands and water plants, although stream and pond creatures are very highly susceptible to almost all other herbicides and pesticides. Used carefully and for specific hard-to-deal-with problems - such as Oxalis pes-caprae - glyphosate can be a real boon.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: ezeiza on March 19, 2012, 05:54:47 PM
Well, Alisdair has answered the detached bulbil question. As for formulas, those aimed at gardens are a lot more diluted than the ones used for crops.

As usual, the glove method is criticized without having even tried it. No paintbrush can be more versatile than the fingers.

As for woody plants, glyphosate affects young ones, just by spraying it on the bark. For larger, older trees, a cut (like with a small axe or a machete) that affects the bark and pure glyphosate on it usually kill them.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: David Bracey on March 19, 2012, 10:20:15 PM
There are several mis-conceptions.

Glyphosate is translocated in the phloem which is why the chemical is effective on perennial weeds; it is tranlocated to the growing tips.  In my experience however it is never truly 100% and a follow-up treatment is generaly necessary.

The herbicidal activity of glyphosate was first reported by Monsanto in 1971. There are several manufacturers of this molecule to-day and it is widely available mainly under the brand "glyphosate". There is no "best" product however some formulations have a higher concentration than others,(ie 120gm to 360g/litre) so read the label for the dosage. To complicate things further there are several salts of glyphosate available. Unfortunately the dose is often referred to as litres (of glyphosate)/hectare rather than as a percentage of dilution. I am trying to check the dilution and will post it tomorrow.

Glyphosate can be safely used around plants with bark.  Glyphosate will only kill plants with chorophyll; it acts via the chlorophyll.

I know of no scientific evidence that the continuous use of glyphosate damages soil structure however there are rumblings in some quarters. It probably revolves around how you classify soil structure. It is true that resistant species have appeared over time including rye grass, Lolium species.

I happily use a knapsak sprayer using standard pressure and a small needle point jet .  This allows you to accurately hit the target without damage to adjacent plants.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: JTh on March 19, 2012, 11:30:12 PM
Glyphosate is supposedly one of the least toxic pesticides around, but there seems to be increasing evidence that it may lead to hormonal disturbances at least in snails and aquatic organisms, and maybe also in humans?
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: ezeiza on March 19, 2012, 11:53:47 PM
In my country, Argentina, and due to the widespread cultivation of transgenic crops, immense quantities of glyphosate are used. Yes, it provokes miscarriage in mammals (most kinds of farm animals) as the wind carries the chemical sprayed by planes. No evidence of soil damage so far but it has been found inside the grains. Small wonder the Chinese and other customers feed the transgenic soybean to animals.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: David Bracey on March 20, 2012, 09:28:55 AM
As promised yesterday............ I use a generic glyphosate containing 360gm/litre.  The recommended use for "easy to control annuals"
is : 50ml in 5 litres of water ie 1%.  The recommended dose for perennials is 70ml in 5 litres of water ie1.4%.  If you use a stronger or weaker product than you need to use proportionally more  less.

I have read Ezeiza`s comments and while it is true that "immense" quantities of glyphosate are used I have serious doubts that there are miscarriages due to its use.  This is an old chestnut.  The agrochemical world is very small and serious problems like this are soon identified and remedial action taken. There are many checks and balances at government and industry levels. 

JTh mentions hormonal damage; what hormone and what damage?  Its too easy to make statements like this without quoting the reference and being serious in a Forum which maintains a very high level of knowledge.

Glyphostae is toxic to most aquatic species and should not be used therefore around ponds, lakes, rivers and run-off areas.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 20, 2012, 09:56:00 AM
David, I don't think you are entirely right to say that glyphosate in itself is toxic to aquatic species, though if other chemicals are added to it - as perhaps they may be in non-Monsanto formulations - these other chemicals may themselves be toxic.
Glyphosate is approved for use around ponds and watercourses in the UK (and I believe in the USA) on the grounds that any toxicity is negligible. One glyphosate formulation - Roundup Pro Biactive - is specifically designed for such use; the glyphosate it contains is the same as in the normal products, but the adjuvants are slightly different.
The reason that glyphosate does not harm non-plant aquatic creatures is that - like all land-based creatures - their bodies do not contain the plant enzymes which glyphosate works by blocking.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: David Bracey on March 20, 2012, 10:04:20 AM
There is an excellent paper entitled "Glyphosate Resistant (GR) Weeds" by Nandula, Reddy et al from the University of Mississippi.

They review the GR problem around the world and identify 7 weed species "naturally resistant" to glyphosate including C. arvensis, Commelina, C. album and A theohrasti.  From my experience I would also include Portulaca oleracea.

"Evolved resistance" due to continuous glyphosate use lists Ambrosia, Conyza species, Eleusine, Lolium , Plantago, Amaranthus tuberculatus.  In general these are not serious weeds of mediterranean areas.

The authors go on to say that if continuous glyphosate use is mainatined there is a good possibility that the usefulness of glyphosate will be diminished.  They go on that the answer is Herbicide Rotation, which of course is good agricultural practice.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: David Bracey on March 20, 2012, 10:13:12 AM
Alisdair you may well be correct that the adjuvants are more toxic to aquatic species that glyphosate.  However  if I read the literature and the French label it definitely states not to use glyphosate around water. 

Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 20, 2012, 11:03:37 AM
I don't know about David's French glyphosate formulations, but anyone wanting to use Roundup safely on or around water will find these detailed instructions (http://www.monsanto-ag.co.uk/content.output/180/180/Roundup/Aquatic%20use/Aquatic%20Weed%20Control.mspx) helpful.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: JTh on March 20, 2012, 12:58:19 PM
I should have been more specific and said that there are some indications that glyphosate  may cause disruption in hormone signalling, here are a few references:

‘Rana pipiens tadpoles chronically exposed to environmentally relevant concentrations of POEA or glyphosate formulations containing POEA showed decreased snout-vent length at metamorphosis and increased time to metamorphosis, tail damage, and gonadal abnormalities. These effects may be caused, in some part, by disruption of hormone signaling, because thyroid hormone receptor beta mRNA transcript levels were elevated by exposure to formulations containing glyphosate and POEA. Taken together, the data suggest that surfactant composition must be considered in the evaluation of toxicity of glyphosate-based herbicides. (see Toxicity of glyphosate-based pesticides to four North American frog species. Howe CM, Berrill M, Pauli BD, Helbing CC, Werry K, Veldhoen N.  http://www.ncbi.nlm.nih.gov/pubmed/15352482)

There is an interview during a meeting in Denmark with Prof. Gilles-Eric Seralini, where he says that ‘My team has noticed that Roundup disrupts hormones (chemical messengers) which are modulating the oestrogen synthesis. Oestrogens are known as female hormones, but today we know that they are important for bone growth and testicular function at very low doses. So a modulation of oestrogen synthesis could account for sperm decline, increase in cancers and sexual malformations. So we have to be careful with the hormonal effects of GM crops and the associated herbicides.’ see http://www.ecochem.com/ENN_glyphosate(2).html

Walsh, L.P. 2000. Roundup inhibits steroidogenesis by disrupting steroidogenic acute regulatory (StAR) protein expression. Environ. Health Persp. 108:769-776. is another  study on effects on hormones. These scientists at Texas Tech University studied the effect of a glyphosate containing herbicide on hormone production. They looked at hormone production by Leydig cells, located in the testes, which play a crucial role in male reproductive function. The scientists showed that exposure to a Roundup herbicide reduced sex hormone production in these cells by 94 percent.

R. Hokanson et al. in their study: Alteration of estrogen-regulated gene expression in human cells induced by the agricultural and horticultural herbicide glyphosate (Human and Experimental Ecology (2007) 26,747—752 wrote: ‘Gene expression is altered in mammalian cells (MCF-7 cells), by exposure to a variety of chemicals that mimic steroid hormones or interact with endocrine receptors or their co-factors. Among those populations chronically exposed to these endocrine disruptive chemicals are persons, and their families, who are employed in agriculture or horticulture, or who use agricultural/horticultural chemicals. Among the chemicals most commonly used, both commercially and in the home, is the herbicide glyphosate. Although glyphosate is commonly considered to be relatively non-toxic, we utilized in vitro DNA microarray analysis of this chemical to evaluate its capacity to alter the expression of a variety of genes in human cells.’

It is probably not glyphosate alone, but the cocktail of this and other factors that may constiute a threat, among them modified insecticidal Bt toxins that are produced by GM plants which have developed resistance to glyphosate, ref. Mesnage R, Clair E, Gress S, Then C, Székács A, Séralini GE. Cytotoxicity on human cells of Cry1Ab and Cry1Ac Bt insecticidal toxins alone or with a glyphosate-based herbicide. J Appl Toxicol. 2012 Feb 15. doi: 10.1002/jat.2712. From the abstract:
‘ In these results, we argue that modified Bt toxins are not inert on nontarget human cells, and that they can present combined side-effects with other residues of pesticides specific to GM plants.’

In a study by Céline Gasniera, et al: Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines. Toxicology Volume 262, Issue 3, 21 August 2009, Pages 184–191, http://www.sciencedirect.com/science/article/pii/S0300483X09003047) they say that it is probably not glyphosate that is the most toxic component in various Roundup formulations, but  that other ingredients in the formulations  disrupt hormone function more efficiently than purified glyphosate. The findings show that the formulations act against the hormones to produce anti-estrogenic and anti-androgenic effects. There is a synopsis of this article here: http://www.environmentalhealthnews.org/ehs/newscience/roundup-mix-more-toxic-to-liver-cells-than-glyphosate/
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: pamela on March 20, 2012, 02:30:16 PM
Thank you Alisdair, Anita, Ezeiza, Jorun and David, I now have a much clearer picture of this. Everyone has been most helpful.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Hilary on March 15, 2020, 09:47:59 AM
Oxalis pes-caprae, Bermuda Buttercup

Looking through THE MEDITERRANEAN GARDEN number 84, April 2016
 I came across an article by Fleur Pavlidis.
 Oxalis pes-caprae: AN INVASIVE SPECIES

This is a very detailed article, about how she copes with this invasive plant in her garden, which I think would be very informative for you who have gardens

Since I don't expect to have a postage stamp depicting this flower, I thought I would go out for a walk looking for the Bermuda Buttercup at the base of trees in the pavement, against walls and in the, mostly untended, beds near the sea. It was a very hot day, for the season, mid-March and in some places the leaves were turning yellow

In the evening I discovered that I did have a stamp and had used it in.this very  Forum.
http://www.mgsforum.org/smf/index.php?action=search2

There is a long discussion about the problem of invasive Oxalis pes-caprae which is where I am going to post this
Since all the places I snapped the Bermuda Buttercup were untended, the feeling that they were invasive and to be destroyed immediately was  missing and they made a cheerful sight.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Charithea on March 16, 2020, 05:06:06 PM
Oh Hilary. The hours I spent removing these Pests.
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Hilary on March 16, 2020, 05:25:18 PM
Yes, but you must admit that under some circumstances they look pretty
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Caroline on March 16, 2020, 11:06:02 PM
Couldn't possibly concede that! Extermination the only answer...
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Alisdair on March 18, 2020, 09:20:26 AM
Hear hear!!!
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: Umbrian on March 19, 2020, 07:47:17 AM
Have to agree with Hilary on this one! ....... but then I have never experienced being overrun with it........let's hope we gardeners have the same staying powers during this crisis :)
Title: Re: Controlling Oxalis pes-caprae (bermuda clover, bermuda buttercup)
Post by: TROPICBIRD on March 21, 2020, 10:15:56 AM
In much of Greece the single Oxalis pes-caprae ("bermuda clover" or "bermuda buttercup") is widespread and completely out of control, carpeting open spaces and olive groves to the virtual exclusion of wild flowers that bloom at the same time. As Alberto says, glyphosate does eliminate it, but those who rely on non-chemical methods find it virtually impossible to exclude this pest from gardens in areas that are infested with it.
Alisdair - did we see that Jordan [MGS trip March 2020] is almost free of Oxalis ?  Here in Cyprus it is now spreading and flowering yellow everywhere at this time of year. What to do? Lilian, Cyprus. xx