Author Topic: Bordeaux mix as Fungicide  (Read 381 times)

fruitnoob

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Bordeaux mix as Fungicide
« on: March 14, 2023, 09:53:26 PM »
I have not found much about Bordeaux mix in this forum and was wondering if it is not effective as a fungicide? The internet claims that Bordeaux mix is a good organic fungicide that has been used since the 19th century.
Has anyone used Bordeaux mix as a fungicide for their trees?
Tom

pagnr

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Re: Bordeaux mix as Fungicide
« Reply #1 on: March 15, 2023, 02:45:11 AM »
The advantage of Bordeaux over copper spray is that it sticks better, and doesn't wash off as quickly in rain.
That should mean less copper applied.
I would still recommend PPE, mask and gloves, eye protection,  when mixing and spraying.
Certainly have used copper and a version of Bordeaux on grapes and Citrus.
Mostly used as an early season preventative spray than are cure spray.

ScottR

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Re: Bordeaux mix as Fungicide
« Reply #2 on: March 15, 2023, 10:46:52 AM »
Lime x Sulphur mix I know my father in law used to make his own but don't know ratio's.

Finca La Isla

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Re: Bordeaux mix as Fungicide
« Reply #3 on: March 15, 2023, 04:29:11 PM »
Copper sulphate with calcium carbonate.
The ratios would depend but I donít think itís very critical.  Iíve used a very C rich mixt to make a paste for treating wounds on trees.  It can be used as a foliar spray.  If youíre interested in using whatís allowed within organics this classic combination is worth experimenting with.
Peter

cbss_daviefl

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Re: Bordeaux mix as Fungicide
« Reply #4 on: March 15, 2023, 11:07:57 PM »
Copper sulfate is used as an algicide and root killer. When using it as a fungicide, it is important to neutralize its acidity (3 to 4) with lime or other plant friendly pH raising agent to a pH of 7. Low pH increases absorption by plants to possibly toxic levels. I believe copper sulfate has been replaced with other copper molecules because it is inefficient and leads to excessive copper accumulation in soil, which at high toxic levels is harmful to roots, blocks iron absorption and disrupts photosynthesis. Copper soaps (Cueva) and copper oxide (Nordox) work similarly as a fungicide with less copper and less worries about pH and toxicity.
Brandon

Finca La Isla

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Re: Bordeaux mix as Fungicide
« Reply #5 on: March 16, 2023, 09:21:17 AM »
Weíve used this Bordelaise mix very infrequently. Microorganisms have worked well for us in most cases for dealing with fungus.
Peter

pagnr

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Re: Bordeaux mix as Fungicide
« Reply #6 on: March 16, 2023, 02:45:29 PM »
Copper sulfate is used as an algicide and root killer. When using it as a fungicide, it is important to neutralize its acidity (3 to 4) with lime or other plant friendly pH raising agent to a pH of 7. Low pH increases absorption by plants to possibly toxic levels. I believe copper sulfate has been replaced with other copper molecules because it is inefficient and leads to excessive copper accumulation in soil, which at high toxic levels is harmful to roots, blocks iron absorption and disrupts photosynthesis. Copper soaps (Cueva) and copper oxide (Nordox) work similarly as a fungicide with less copper and less worries about pH and toxicity.

Thanks, you raise important points.
Copper Oxychloride is used heavily on grapevines around here, the Cu issues are a concern after decades of use.
As Copper Oxychloride washes off with rain, several sprays are required per season. Overhead irrigation will be the same.
If Bordeaux spray persists better, less sprays may be required per season.
That may or may not be less actual Cu Copper applied over time, depending on the chemical formulation and spray formulation.
The same for the other copper products.
I have used Copper Oxide, seemed similar holding to Oxychloride, but that is just a just an observation.
The Bourdeaux mix proportions of Copper and Lime will affect activity of the Copper, probably the persistence on the leaves and ease of spraying through nozzles.
Highly efficient low volume spray nozzles will allow good leaf coverage without using too much spray mix. ( for all  Copper sprays ).
To dilute the amount of Copper applied and increase the stick, I used Copper Oxychloride and powdered milk as a painted paste on trunks and wounds.
Somewhere between 30% Copper & 70% milk powder to 50/50 each.
As for Copper toxicity issues, those with a few trees sprayed can collect the fallen leaves and dispose or burn/ compost and spread more widely around than just under the same tree.

cbss_daviefl

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Re: Bordeaux mix as Fungicide
« Reply #7 on: March 16, 2023, 03:15:30 PM »
If copper is sprayed only 3 or 4 times a year using copper soap or copper oxide, there is no reason worry about soil accumulation. Copper is a vital nutrient to plants. It is sometimes added to fertilizer and trees that are never or rarely sprayed may suffer from copper deficiency.

I agree using a spray sticker in the fungicide is important to extend the time of the fungicides effectiveness and keep the copper from washing off at the first rainfall. Nu Film 17 or Nu Film P are products that help with this.
Brandon

fruitnoob

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Re: Bordeaux mix as Fungicide
« Reply #8 on: March 16, 2023, 11:15:56 PM »
This may not work for me. Bordeaux mixture is a dormant spray and may/will damage new growth. I am OK with horticultural oil for dormant spray. I am looking for an alternative, preferably organic solution to use during active growing season (to prevent anthracnose.)   I am using copper fungicide and I am concerned about copper buildup over the years to come.
 
I will need to read more about this.
Tom

pagnr

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Re: Bordeaux mix as Fungicide
« Reply #9 on: March 17, 2023, 02:40:28 AM »
If copper is sprayed only 3 or 4 times a year using copper soap or copper oxide, there is no reason worry about soil accumulation. Copper is a vital nutrient to plants. It is sometimes added to fertilizer and trees that are never or rarely sprayed may suffer from copper deficiency.

Fertilisers with trace elements contain a Copper addition. That is at a rate usually sufficient for growth.
Straight NPK fertilisers probably have zero Copper.
Spraying supplies extra Copper, it may add up depending on other fertilisers or natural levels in the soil.
Copper sprays are well known, but that may not mean you can't overdo it.
If you can, spray the least effective amount, either by formulation, stickers, or spray nozzles.
Plants in containers with pot mix might be more at risk from excess copper than plants in the ground, where the soil can act as a bigger buffer.
I once collected a lot of grape vine canes for basket weaving, but borers got to them.
When I burnt them I was impressed by the beautiful blue green tint to the flames, I guess from the previous copper sprays ?

Plantinyum

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Re: Bordeaux mix as Fungicide
« Reply #10 on: March 17, 2023, 03:04:51 AM »
I have been using bordeaux copper sprays for several years, i do several dormant sprays each year, 4 sprays in total ,2 in the fall and 2 in the spring. I think it has a good effect at keeping away most of the fungal issues on stonefruit, doesnt work quite well on apples in my experience. My peach and nectarines have always been very leaf curl free and fungal free in general, whereas i see other peoples peaches that look like garbage in the summer, leaf curl is a big problem here, without spraying.
Definitely should not be used on leaves ,especially on peach and nectarine, i was constantly spraying my peach several years ago,during summer. I was puzzled as to why the leaves were falling off green and looking sick overall. The tree almost completely deffoliated that year. Later i did a research and found that copper is toxic to leaves so it was burning my peaches leaves, i found this on my own , the lady at the agro store just kept selling me the bourdeaux solution, without telling me about the effects it had.....

 

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