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Fighting tomato blight with pennies?

using a copper penny circa 2008 to fight blight with antimicrobial effect of copper


According to wikipedia there are molecular mechanisms within copper that can control a wide range of molds, algae, fungi, and microbes.

We've been cutting off new tomato flowers to divert energy to fruit and I thought it might be a good time to try an old wives tale I heard down at the hardware store a few years ago.

If it slows down the blight even a little it'll be worth the effort.



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Finally a great use for all of those old pennies we all have! I have read of several uses for them, but this is a new one for me. I look forward to hearing how well this worked! :)
Comment by Jami @newbiehomestead Sun Aug 26 14:09:15 2012
Just my 2 cents (ha,ha), you may want to use pennines that were minted before 1982, if possible. They actually have some COPPER in them! ;)
Comment by Wilder Family Sun Aug 26 14:25:25 2012

Jami --- We'll be sure to post a followup. I suspect this penny trick would be most effective if used early in the season before blight hits the patch.

Wilder Family --- Excellent point! Mark should probably go digging for an older penny --- I didn't realize modern pennies had no copper at all in them.

Comment by anna Sun Aug 26 14:58:55 2012

Copper is a well-known biocide, and was used as such even before the concept of bacteria and viruses was known. E.g. water transported or kept in copper vessels didn't develop a slimy layer on the inside of the container.

But is is not just copper. Its alloys can have the same antimicrobial properties, but to a somewhat lesser degree. What is really cool is that copper also works well against some viruses and fungi.

If you can't find copper pennies, use red copper water pipe. I'm not sure how common that is in the US; here most houses have copper freshwater pipes.

Based on this, I had another idea to protect your tomatoes; IIRC, you seem to have observed that the lower leaves are blighted first.

To protect your tomato plants (after you've tied them up) I propose you put some fine copper(-plated) mesh around the plant, parallel to the ground, a couple of inches up. The mesh should intercept dust particles as the rain splashes them up, while the copper wreaks havoc on bacteria and possibly spores that touch it. It also keeps the leaves off the ground.

Comment by Roland_Smith Sun Aug 26 15:31:26 2012

Roland --- Great ideas, as usual. By the way, I did a few seconds of research and found out that even modern pennies have a very thin coating of copper, which I'll bet is sufficient for the use Mark is putting them to. And I think we have some copper water pipe in the barn, too.

I wonder if it would work to have a circle of copper-plated mesh on little feet that you put a few inches above the mulch? I like your idea of focusing on the real problem, which is splashing up from the ground. I don't want to put the copper directly on the ground, though, because it could kill the important soil microorganisms. I'll bet there's a microbusiness product there if anyone wanted to test it out....

Comment by anna Sun Aug 26 18:55:49 2012
Pennies still have copper. That's why they appear to be copper. They are copper-plated zinc now instead of pure copper, but since the copper is still on the outside, new pennies should work just the same as the old ones for this purpose.
Comment by Angela Sun Aug 26 21:46:52 2012
I found out early in the year that "spraying" my tomatoes with copper(Sticky green stuff made for just this purpose) held the blight in check all summer. I have harvested so many tomatoes this year I'm going to have to resort to throwing them at things just to get rid of them.
Comment by Anonymous Sun Aug 26 21:47:16 2012

Angela --- Yep, that's what I eventually learned after I did some research. Lots of fascinating information out there on the internet about copper content of pennies!

Anonymous --- Spraying on copper is the mainstream "organic" way to prevent blight, but it's a very strong treatment that I don't really approve of. The copper ends up in the soil, where it kills essential soil microorganisms and can also build up to problematic levels for plants after a few years. That's why we work around the blight rather than spraying copper. Although I'm not so sure Mark's technique will do any good, it will also have the benefit of doing no evil since the copper is unlikely to end up in the soil in more than miniscule quantities.

Comment by anna Mon Aug 27 07:58:07 2012

Since metallic copper does not dissolve in water, I don't think placing copper mesh directly onto the ground will do much harm (as opposed to the soluble copper(II) compounds that are usually sprayed on plants)

But putting the copper aboveground just to be sure was exactly what I had in mind;

  • Make a U-shape out of three pieces of wood, each say 7" long, 2" wide and 1/2" think.
  • Lay the U-shap flat, and staple a 7"x7" piece of copper mesh onto the top of it.
  • Cut the mesh from the middle of the open end of the U-shape to the center of the mesh. Make a little hole at the end of the cut so the stem of the plant will go through.
  • Use the cut in the mesh to place it around your tomato plant.

This should put the copper mesh 2" above ground. You could even fill the space under this contraption with straw as an extra mulch to keep the competition out.

Comment by Roland_Smith Mon Aug 27 10:15:36 2012
Roland --- So, would you use something cheap like this or do you think you need copper screen?
Comment by anna Mon Aug 27 16:33:50 2012

Hmm, I can't seem to find a composition for the stuf-fit, other than that it of composed out of "various metals". And it looks like its braided rather than woven, so it might come apart when you cut it open to lay it flat.

The more expensive stuff is 90% copper with 10% zinc, so technically a brass. Presumably to keep it from oxidizing quickly. That seems like a good idea.

I would go for a relatively fine woven mesh, say 20 wires/inch, like e.g. this one. I think you could find stuff like that at an arts & crafts store, or at a place that sells electronics (as faraday shielding).

Bottom line: go for a high copper content (but probably not pure copper; brass corrodes less quickly AFAIK), and a relatively fine mesh.

Comment by Roland_Smith Mon Aug 27 17:43:31 2012

Of course the way to learn the most is to do a carefully controlled experiment with different meshes, but that almost goes without saying, I guess.

  • Use two (or maybe three but not more) different meshes. Choose one that you expect to perform well and one that you think might perform poorly. Realize that the more variables you add, the bigger the combinatorial explosion of possible interactions is, and the larger the number of experiments that you need.
  • Use them on plants close together, to exclude other variations such as sunlight, soil condition, water, as much as possible.
  • Confine the experiment to one kind of tomato plant, again to exclude unintended variation.
  • Use controls (without mesh screens) for comparison purposes.
  • Use as many plants as possible to get statistically sound data (at least 5 but preferably more for every kind of mesh).

For more info, read up on "design of experiments" (DOE).

Comment by Roland_Smith Mon Aug 27 18:08:37 2012

Roland --- Our terrain is so varied that if I wanted to get any semi-definitive results, we'd have to stick to one experimental treatment and a control, alternated throughout the garden beds. That's why I was wondering which type of material you recommended --- sounds like the twpinc one might be our best bet.

Now lets see if I remember I wanted to try this come next April.... :-)

Comment by anna Mon Aug 27 19:22:37 2012
I love this! Although DH would certainly think that I have lost my marbles:) (Which is ok, because almost everytime I dig in the garden, I find marbles! Literally:D)
Comment by MamaHomesteader Tue Aug 28 00:15:00 2012
Making some of these sounds like a good job for a winter day, so you can get them ready before planting season.
Comment by Roland_Smith Tue Aug 28 03:07:58 2012

MamaHomesteader --- There was a marble factory close to where my father grew up, and my memories of visiting my grandmother involve a lot of digging up marbles. But maybe your yard just housed marble-playing kids before you?

Roland --- Good idea. :-)

Comment by anna Tue Aug 28 14:12:23 2012

Interesting, never heard of this before! I've got some scraps of 2-conductor electrical wire (the stuff that is used to wire up your outlets, etc); I'm thinking the solid copper conductor, snipped off with a wire cutters, will have a nice pointy end that could be easily embedded into a stalk - I think I'll try this next year!

Comment by Bob W Fri Aug 31 10:38:53 2012
Bob --- I'll be curious to hear what happens if you try it out!
Comment by anna Fri Aug 31 19:28:05 2012
I had a mold/fungus problem with our peach trees this year. Thoughts on putting pennies/copper on branches?
Comment by Glenda Tue Oct 2 12:21:41 2012
seems that it might help there as well. can't wait for next spring to try!
Comment by Anonymous Tue Oct 2 13:24:21 2012
i love to read and learn about the many ways to protect what you grow and harvest...please continue as i find this so helpful in my efforts to keep fresh produce and products for canning available and in abundance..thanks everyone!!!!
Comment by Diane Tue Oct 2 15:11:31 2012

I friend sent me this link:

http://www.lenntech.com/periodic/elements/cu.htm

Any comments?

Comment by Carol Bland Tue Oct 2 15:33:12 2012

Glenda --- It might take a lot of pennies to protect a whole tree. But Roland's suggestion in the comments might work --- some kind of copper netting.

Anonymous --- If you give it a try, I hope you'll come back and tell us about it!

Diane --- Glad we could help.

Carol --- That's related to the reason I'm not a fan of the copper sprays that are allowed in organic production. The benefit of using something like a penny instead is that the copper shouldn't end up in your food (and in the soil) --- the metal stays put where you place it. Of course, the question is, does it do any good?

Comment by anna Tue Oct 2 16:26:27 2012
use stranded copper wire just unravel and take a strand and insert it into your tomato a lot better than useing a penny.
Comment by silver Tue Oct 2 18:18:22 2012

thanks people our growing season is just beginning and i'm growing in a new area, CBD auckland NZ, the neighbours are not gardeners, this blog has been sent by the vege Gods.

Mauriora = health and wellness to you

Comment by therese Wed Oct 3 01:37:28 2012

Silver --- That does sound like a good alternative to experiment with.

Therese --- So glad to help you find an online community! We are definitely passionate about gardening here. Love your "vege Gods" comment. :-)

Comment by anna Wed Oct 3 13:08:53 2012
Copper also kills the good bacteria and funguses in the ground and apparently you have to work years to get them back. A viable alternative is Milk or aspirin. New Zealand Agricultural uses milk in a 1 pt to 9 pts water solution and I have had good results with it as well... oddly enough if you put milk on a child's eye who suffers from pinkeye the milk will kill that fungus too. I am not sure about the aspirin solution but it is used to keep black spot and other funguses off of roses. You could look that up easily as it seems to be a common practice.
Comment by Anonymous Wed Nov 21 10:18:17 2012

The copper penny or wire is better than sprayed copper. As the copper oxidizes from the penny or wire the rain or water will leach it into the soil. There is less chance of soil contamination from copper this way. But the better way is building up the lacto-bacteria by adding milk or milk products and then you get calcium too.

When I plant my tomatoes I add two tablespoons of powdered milk, green sand, bone meal and epsom salt. Later if there is any sign of blight keep sprinkling powdered milk on and around the plants. It promotes the lacto-bacteria that attacks the blight.

One of the best things you can do though is to stake the plants and keep the bottom leaves trimmed up so that they don't touch the ground and are high enough so that soil doesn't splash up on them. The lower leaves are not a big sacrifice for the plants.

Comment by Judi Tue Feb 5 09:42:53 2013
I just read your comment about BLIGHT on tomato plants, what is tomato blight ?
Comment by JANET Thu Feb 7 18:31:27 2013
I really think the powdered Milk dusting would be the best, and I'm sure gonna try it to find out.
Comment by Sarah Thu Feb 7 18:57:38 2013
Can't wait to try out this idea.
Comment by Vicki Hudson Thu Feb 7 19:15:53 2013
Janet --- The term blight is used to refer to any one of various kinds of fungal diseases. You can read our main techniques of fighting blight here. Pruning definitely slows things down....
Comment by anna Thu Feb 7 19:24:25 2013
Could you spray the copper spray onto a brush and brush it lighting on the stalk of the tomato plant? That would keep it out of the soil.
Comment by CarolAnn Thu Feb 7 20:13:02 2013

powdered milk is great for tomato's. It puts calcium in the soil. Here in Texas we have some intense heat in the summer, I put my tomato's out in February same time you cut back your roses,2-14. I get a large amount of tomato's in the spring, when summer comes I water in the powdered milk, because tomato's need extra calcium when they are stressed by the heat, they kind of go dormant in the summer, then when it cools down I get another flush of tomato's until we get a frost if I don't cover them, I will lose them, but they grow almost all year here. Another good thing is milk of magnesia, it puts magnesium back into your soil, which is what is lacking if your leaves start to yellow, also works on roses. I know this because I am a Master Gardener here in Texas. So these things do work.

Comment by Judy Thu Feb 7 20:34:15 2013
jut a thought maby use copper tubing for irrigation
Comment by kevin Thu Feb 7 20:38:01 2013
I have been gardening for years, and have fought tomato blight just about as long. Copper is expensive, and since Ive cashed in all my pennies, I would like to give you my 2 cents worth. Blight is caused from bacteria being splashed back up onto the plants when it rains. Several years ago, and with lots of research, this is what I do. When setting out my tomato plants, the first thing I do is cover the row with black plastic, securing the ends with something solid. Cut slits into the black plastic, set my tomato plants into the ground where I cut the slits, and cover the entire row with straw. The plastic creates condensation, so you never have to water after the initial planting, and the straw helps prevent sunburn, no weeds, and no blight.
Comment by Shirley Braley Fri Feb 8 10:50:00 2013

To respond to the comment about using black plastic to prevent blight, this is true and effective to prevent soil borne blight. But late blight comes with the rains, it can be carried on the winds so you need the powdered milk solution or the copper solution.

Another possibility is using compost tea. Compost tea has a plethora of bacteria and some of them fight blight, plus compost tea is super for the soil both nutrient wise and adding beneficial bacteria to the soil.

I have also seen people using copper wire strung along the top of the stakes or tomato cages, to allow copper to be gradually oxidized and released into the soil. This way only minute quantities are released into the environment, but enough to be effective.

Comment by Judi Fri Feb 8 12:23:10 2013
How about using wire from old applicance? Perhaps rolling it around the stems a coulple of times rather that tossing out the appliance. Good way to recycle?
Comment by phylis Fri Feb 8 18:47:48 2013
I'll try the penny trick on my tomatoes to fight blight this year!
Comment by Tom Sellers Fri Feb 8 19:20:45 2013
This has nothing to do with tomatoes, but if you put copper in a water tank for animals it keeps the water clean. We use it for our horses
Comment by PAULA CLOAT Fri Feb 8 21:12:50 2013

Thanks to the power of Facebook I got to read this article and am fascinated.

Perhaps by inserting the penny, or other copper item, in the main stem of the plant, the effect could be dispersed throughout the plant allowing fast and efficient protection without too much investment. Will be great to read updates through the season, though hopefully it won't be a blight affected year. Thanks for documenting.

Comment by sam Sat Feb 9 02:44:07 2013

The contributors thus far have taken two positions on copper- that it doesn't dissolve in water, and that it will travel through the tomato plant and inhibit blight. It can only do that if it is at least a little soluble in water.

I see a lot of speculation, but not so many that have said that it worked for them. Are there more people who have tried it, maybe on some of their plants and not on others, and what happened?

Comment by Halhurst Sat Feb 9 15:20:45 2013
Warning copper makes an excellent ground..... and could make for a good lightning rod when using copper mesh and the like.... if your area is prone to lighting.... keep that in mind in case of storm....
Comment by JB Tue Feb 12 21:49:11 2013
Copper Pennies, who Knew??? Glad you did!! I love tomatoes now I will Love them a whole lot more!! Thank You!
Comment by Tammy Lunsford Sun Feb 17 18:59:01 2013
My grandpa used to plant a penny in the ground under the root of the tomatoes every year. I thought he did it just because. Well, I plant tomatoes in big totes on my porch as I cannot bend down to plant in the ground. I always put a penny where I dig the whole to plant the tomatoes. It seems to work as I never have problems and it doesn't go into the regular ground and I never have weeds and I have big good tasting tomatoes. To keep the potato bugs off those and the roses, I used flour and have the old fashioned sifter and I sift the flour on the plant. Works every year. No bugs and the bees still come around to do whatever they are supposed to do.
Comment by Judi Sun Feb 17 20:55:32 2013
If you want free copper consider new construction sights. Most electrical contractors leave behind there scrap after completing a project and may take kindly you to picking it up. I would ask permission first and also understand you will need to strip the wire of any insulation. Maybe 6" lengths hooked at one end and decorate your tomato plant like you do your Christmas tree.
Comment by James Tomato Tue Feb 19 13:49:07 2013
A penny can be used to made a blown fuse work again in most cases. When one of your round fuses blows, unscrew it and put a copper penny in the socket them re-screw the bad fuse back in. Most of the time it will work until you can get a replacement. I have used it many times since the 1070's.
Comment by deborah Fri Apr 5 19:20:40 2013
Copper was used in paint on the bottoms of boats that sat in a marina to prevent marine growth. Then it was discovered that all the copper that leeched out of that paint ended up in the mud beneath all those marinas. Needless to say, copper is no longer used in marine paint.
Comment by FYI Fri Apr 5 20:59:07 2013
I have found that a few pennies in a plastic bag of water hung on the back porch keeps some of the millions of flies away from my grill etc.
Comment by Anonymous Sat Apr 6 06:50:48 2013

Since 1983, US pennies are made from zinc, which is only copper-plated. So the copper content is only 2.5%.

Pure copper itself doesn't dissolve in water. It does slowly oxidise in water containing oxygen and carbon dioxide, which leads to copper ions on the surface that readily dissolve. The mechanism is explained in this paper. This will dissolve up 30-50 mg/m2/day depending on the oxygen content of the water. In other words, it will take a year for at most 280 grains of copper to dissolve from 10 square feet of copper!

Comment by Roland_Smith Sun Apr 7 11:38:31 2013
Copper fungi side also known as Bordaux mixture , found accidentally in the 1840,s when mixing lime in copper vessels to spray on grape vines
Comment by Bullnettle Tue May 28 21:27:03 2013
You need to make sure the pennies are copper and not the zinc ones.
Comment by Rickb Sat Jun 8 19:11:26 2013

I actually bought some of these copper scouring pads in order to do this. I am planning to cut the pads and wrap a few strands around the plants. Will try the powdered milk too. Blight has been a huge problem in our area. http://www.yaysave.com/catalogsearch/result/index/?cat=1215&q=copper+scouring+pads

Comment by GPeterson Sat Jun 8 23:48:42 2013
You can try the pennies but research copper deficients in soil. A fungicide that is available and is also used by some farmers to fight bacteria in barns is wood mulch. The wood begins to rot and this releases fungicides which are also anti bacterial. Try also using wood chips for mulch in your tomato garden. Also check out how magnesium enters in blight control . (epsom salts) and other minerals. Research complimentary plantings as well. I.E. Marigolds are great to control Japanese Beetles on Green and yellow beans. In many new , old housing developments there is great imbalance of mineral content in soils. Remember to search for tomato varieties that have best blight free histories.
Comment by Anonymous Sun Jun 9 16:49:04 2013
As co-owner of a construction business I must also comment to the post about putting pennies in fuse boxes. This is a very dangerous practice and can cause a fire very quickly as it will get very hot very fast especially if you are having fuse problems and the fuse box/wires are already compromised. I have seen many burn spots in old fuse boxes that very well could have started a fire inside the wall.
Comment by Lisa MAllory Mon Jun 10 13:11:53 2013
My husband works at a flour mill so we have plenty to use on the garden.It constipates the pests and I also use powdered milk.works great.
Comment by laurene Sun Jun 16 16:35:20 2013
Instead of using pennies to fight tomato blight,  you may opt to use Liquid copper!!!  It is available at most garden supply stores or a store such as Lowes!
Comment by Sammy D. Ellzey Mon Jul 1 19:14:17 2013
So, how many pennies per plant do you use? And where do you put them? A little more info on this is done would be helpful. Thanks! (If I missed a post on this between the use of the copper mesh, etc., I apologize)
Comment by fdlstyx Tue Jul 2 18:31:12 2013
Or you could just use natural fungicides. The products I use in my gardens are all derived from plants, some are indeed toxic, but not like regular store bought chemicals.
Comment by Anonymous Tue Jul 2 18:44:32 2013
For a natural fungicide try neem oil, said to be great in controling stink bugs too.
Comment by Tim Wed Jul 3 22:34:53 2013

copper will do some thing that is sure. my antenna for my radio hung over the roof of my house, and directly under the antenna there was no fungus growing, but off to each side the roof was black with it now the shingels looked just like new where the antenna hung over it I will try to see if some copper wire will help on tomato blight .

Comment by michael Fri Aug 2 21:44:57 2013
I had never heard of doing this before, but I am going to try this method to see if it works for me :)
Comment by Diane Avans Fri Mar 7 09:15:24 2014
Hi, just found this site and thought I would share something that works great for me. When you set out your tomatoes, add a Penny, (I boil mine first....just to get rid of whatever germs are on it), and add one or two Tums or Rolaids in the hole. Blossom end rot is due to a calcium deficiency and Antacids are calcium supplements. Since doing this 4 years ago, I went from having B.E.R. every season to not having any plants suffer with it!! Simple, effective, cheap and easy. Try it! Also, when using this method I've consistently gotten 2-3 lb Mortgage Lifter tomatoes every year since!
Comment by Craig Thu Apr 10 03:01:05 2014

I just came in from placing pennies in my tomatoes. While the blight hasn't been as bad as previous years, it still has affected my tomatoes by "creeping" up the vines after lower tomatoes have been picked. my vines are over 7 ft. tall and producing very well. This is first year that I haven't had blossom end rot and I attribute that to the amendments I used all season so far - a boron (borax), Magnesium (Epsom salts), and Dolomite lime mixture I read about online. I have exceptional results in my raised beds and Earth Boxes! However, my tomato vines are getting "leggy" as I keep getting rid of leaves and limbs showing the blight. I still have huge tomatoes on my Beefsteak and Mortgage Buster tomatoes. I'm going to try the powdered milk in addition to the pennies and I'll try to let you all know how it goes. I'm also going to put a penny near the roots of my Roma tomatoes that are just beginning to bear fruit. Thanks to everyone for their input here. Much appreciated.

Comment by Sharon Mizell Fri Jul 25 16:00:29 2014