New & Improved Calcium for Botrytis Thread

michaelg(7a NC Mts)September 12, 2007

The other thread has enough mistakes and false starts to get Thomas Aquinas all confused, so let's start over.

--There is ample scientific evidence that getting extra calcium into rosebuds reduces botrytis flower blight in cut roses by 2/3 to 4/5 and increases vase life by 1/3. Only greenhouse hybrid teas were studied, but the findings should have some pertinence for gardeners.

--Botrytis causes balling and rotting of flowers, red-spotting and brown rotten spots on petals. It also causes black cankers and dieback of green canes and gray mold on cuttings. One study found that extra calcium as a spray reduced botrytis stem lesions on tomato. Calcium has also been shown to control several other fungal diseases, especially on fruit.

--Calcium strengthens resistance to fungal attack by strengthening cell walls. It slows the aging of flowers and reduces production of ethylene gas. In one study, the high pH of calcium sprays was thought to reduce germination of botrytis as well.

--In various studies, extra calcium (beyond normal nutrition) was successfully applied in three different ways: through vase water solutions, by spraying buds before harvest, and by feeding through the roots. However, in fertigation experiments, little extra calcium reached the flowers when normal levels of potassium and magnesium were in the nutrient solution. This finding suggests that applying calcium to the garden soil wouldn't accomplish the full benefit.

--Calcium is not very mobile in plants and would not be translocated much if any from leaves (which would be a "downward" movement from leaf to stem), so buds and their stems need to be treated directly or from the roots.

--Various calcium salts were effective in the experiments, including calcium sulfate, calcium nitrate, and calcium chloride.

--Calcium sulfate--

I have been experimenting with garden gypsum, which is impure calcium sulfate dihydrate. It is slow to dissolve and will not form a strong solution. However, there is a convenient way to get a solution. Put 1 tb. gypsum in 1 gallon of water (for example, a clean water jug) and let stand for a week at room temperature. This should produce a solution suitable for spraying (10 mM to 25 mM). Pour off the solution, leaving the sediment. It's a good idea to measure the sediment at least once to see how much is dissolving, which will vary according to the purity of the gypsum and the fineness of particles. I recovered 1 tsp of sediment after a week, so 2/3 of the gypsum dissolved. If you get more than 1 tsp sediment, start with 4 tsp/gal next time so that at least 2 tsp dissolve in a week. The pH of my solution, without the spreader, is neutral.

I have sprayed this solution three times on some stems with no mechanical problems or damage to petals or leaves. Once I combined it with sulfur fungicide. A surfactant (spreader) is needed. I used one tsp/gal of insecticidal soap or dish soap. The scientific studies used a non-ionic surfactant, Tween 20 (polysorbate 20).

One could spray the whole garden or just spritz buds and flowers with their stems, especially those intended for cutting or exhibition.

For vase solution, dilute the spray solution with 3 parts water.

We haven't had much botrytis weather since I took this up. I have been comparing recently-sprayed with unsprayed-for-17-days buds of the same susceptible varieties. I wet them one evening before a cool night, 5 days ago. Although there is no severe botrytis on the control group, most flowers have minor symptoms. The recently-sprayed flowers are almost entirely clean. These stems were sprayed 3 times so far at weekly intervals, but there is probably little benefit from the older sprayings. Sprayed flowers seem to last longer as cut flowers.

--Calcium chloride--

This is available as ice melting and dust control products. Agricultural grade calcium chloride would also be sold in farm stores in areas where apples and other fruits are grown. Calcium chloride has more calcium than the other forms. Although it is more phytotoxic, it is commonly used in agriculture because it dissolves easily.

I haven't tried spraying calcium chloride, but I have used an impure form sold as ice melter in vase solutions. It seems to extend vase life.

Vase solution: 1/8 teaspoon/quart. Do not combine with bleach.

Spray: I would try 1 or 1-1/2 tsp/gallon, with a spreader. Solutions of 3-4 tsp/gal are used on apples, but are said to be phytotoxic to apple foliage above 81 F. Calcium chloride is said to be compatible with fungicides normally used on apple.

--Calcium nitrate--

Commonly available as fertilizer, it dissolves readily with a small amount of sediment. A fully soluble or greenhouse grade is also produced, and this could be used if there are any mechanical problems with the fertilizer. I have not experimented with it.

Vase solution: probably 1/4 tsp/quart.

Spray solution: probably 2 tsp/gallon, with spreader, dissolved separately before adding to the tank without the sediment.

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Thanks Michael for the great summary. Right now it is raining (I hope it will rain for several hours) so after it clears I will (need to )try this solution.

    Bookmark   September 12, 2007 at 3:44PM
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I made my way through all of the last thread. Thank you for updating this and for the info. Annie

    Bookmark   September 12, 2007 at 5:28PM
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It works! It definitely, positively works! I will apply it again on the coming weekend. Now, however it's time to try to locate calcium chloride for my roses - after the end of October I usually do not give them nitrogen, so I am a bit afraid that calcium nitrate would push new growth.

Thank you MichaelG for posting those papers and thank you for the summary. I truly appreciate it.

    Bookmark   October 11, 2007 at 1:46AM
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I'm going to try it as I have a few plants that consistently have ruined blooms due to botrytis. Thanks for your experiments!

    Bookmark   October 11, 2007 at 7:04AM
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michaelg(7a NC Mts)

It does seem to work, and if you aren't adding it to fungicide, it works to just spritz budding stems, buds, and flowers, especially the green stems below buds. As I understand it, calcium taken up by the leaves can't reach the flowers, but calcium absorbed by the stems can do so. However, it's possible that extra calcium in the whole plant might increase resistance to other fungi (no evidence for that).

I have been planning to SP Hawkeye Belle because 95% of the flowers are ruined by botrytis. I've been getting clean flowers ever since I started using gypsum solution. We have had some weather conditions that would spread the disease. Incidentally, symptoms seems to appear on the fourth day after wetting that is followed by cool to moderate temperatures.

On the other thread, I mentioned a fine filamentous material that sometimes "grows" at the bottom of the gypsum solution. This seems to be very fine crystals coming out of solution, and if shaken it doesn't clog even a mist sprayer.

Ceterum, why don't you use gypsum instead of calcium chloride? It isn't inconvenient if you follow the instructions in the original post. But you could probably find CaCl2 ice melter in the Piedmont cities during the winter months.

    Bookmark   October 11, 2007 at 9:44AM
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I checked for gypsum at Lowe's where they usually sell it in 3-5 lbs bags but they do not have it know - garden stuff is out, Christmas ornaments are in. I do not want to buy 50lbs at Farmers supply stores because I do not have space to store it. I was thinking to make a trip to Raleigh for C. chloride but I think they will not have it now and by the time they sell it, I will not have buds to spray. But I will figure out something, it really works. Maybe I will not even SP/give away Clotilde Soupert (among others)if I find an easy solution to spray her regularly.

    Bookmark   October 11, 2007 at 11:16AM
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michaelg(7a NC Mts)

In your climate, I doubt if you would have any serious consequences if you continued with the calcium nitrate. I'm very glad to hear you feel you got positive results.

    Bookmark   October 11, 2007 at 1:09PM
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Wow,thanks for the info. It is too late for this year here-well I suppose Clotilde Soupert will ball a few flowers yet- But I will difinitly try this next spring. botrytis has to be the worst problem here...


    Bookmark   October 11, 2007 at 1:25PM
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michaelg(7a NC Mts)

Ceterum, what exactly did you do with the calcium nitrate fertilizer? How often? How are you judging the results?

    Bookmark   October 11, 2007 at 3:26PM
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Michael, I am at the beginner stage. I filled up 7 or 8 one gallon milk and similar jugs with water added to the calcium nitrate per your instructions (2 teaspoon per gallon)* about 10 days ago or so. First I tried to use a misting bottle (about two weeks ago) but that wasn't good enough because I could not spray/mist the climbers or some of the very tall HTs like Folklore, Impeartrice Farah, etc. Needless to say before I could follow up with the Rocket sprayer we had a sprinkle (didn't qualify to call it rain) the next night and the blooms of Marechal Niel, cl. Peace Imp. Farah, Elina and you name it balled terribly. (Not that I needed any sprinkle in that thick humid steam bath with regular dews every morning we had for weeks to see almost everything ball).

So, last weekend DH sprayed the roses with Bayer+ Response+Avid in the morning and when the roses dried of that treatment, I filled up the Rocket sprayer with the calcium nitrate solution with some dish soap added, and sprayed all roses - only the top third or where I saw buds and yes, even open flowers. I needed to bring a huge bouquet to the garden club on Tuesday and I was curious if some of the already open flowers would hold on from Saturday to Tuesday. They did and they didn't even look tired.
I also cut a few blooms for my desk - some were fully opened; I would not bother to cut flowers in that stage to bring in as a rule but I was curious.

On Tuesday I cut pristine cl. Peace blooms, Elina, Folklore, Imp. Farah and Buff beauty for the garden club bouquet and I enjoyed seeing Clotilde Soupert, Great Century with perfect, clean blooms. The wide opened Memorial Day bloom I cut Saturday evening lasted till today. The cl. Peace blooms that opened are in sharp contrast with all those that I had no time to deadhead yet and were not sprayed with calcium nitrate prior to Saturday.

I didn't check Marechal Niel but looking out my study now I see open, clean blooms; no brown 'mop heads', no red spots, circles or stripes on the newly opened blooms. And the buds of Belindas dream that opened after Saturday are not rotten brown but pink and healthy.

I am aware that this is not a long enough experiment to qualify it any way to call it 'scientific' but I was thrilled that I could see unblemished blooms at long last.

I didn't do any control this time because I was just sick and tired of seeing only blemished blooms in the last month or so. I know, I know that I should have but I just could not stand seeing any more rotten blooms. Sorry about that.

For sake of comparison: DH sprayed 25 gallons of Bayer and al to treat all roses, I sprayed 5 gallons of calcium nitrate, 6 would have been better and enough; because of the drought I do not have that many flowers as I should in mid-October.

* I expected that I should use a filter not to clog the sprayer but there was no need for that, the calcium nitrate dissolved perfectly.

    Bookmark   October 11, 2007 at 7:09PM
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michaelg(7a NC Mts)

Ceterum, since the calcium nitrate dissolves so much better than gypsum, maybe you don't need to be messing with the jugs. You could dissolve 4 TB in a half gallon and add it to your 5 gal of spray.

    Bookmark   October 12, 2007 at 2:54PM
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Yes, but I wasn't sure how well it would dissolve. When I made the first solution many weeks ago (after your first thread-post to use it for cut flowers in vase, I found a bit of sediment on the bottom; but I didn't wait enough plus I used too much, 2 tablespoon - not for a gallon but for a bit more than a quart. You may remember I terribly burnt the flowers with that stuff. So I thought I should be more careful this time and print out and follow the instructions step by step. Besides, I wasn't sure how much I would need. It is not a big deal to fill up several jugs anyway. I didn't store them in hot sun however.:-)

    Bookmark   October 12, 2007 at 3:38PM
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Michael, I'm wondering if you are comparing improved vase life in your flowers with ones that were in, say, a commercial preservative (like Flora-life, which is what I normally use), or with ones that are in only plain water. Or in other words, do you think it is worth it to add calcium to water that already has a preservative in it, or is that overkill (no pun intended).

    Bookmark   October 15, 2007 at 10:49PM
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michaelg(7a NC Mts)

I was comparing with plain water and so were the scientific studies. One study compared calcium with particular ingredients in standard preservatives, but not with the combination.

    Bookmark   October 16, 2007 at 9:43AM
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Thanks so much for this info. I deal with an ongoing case of botrytis pretty much year round on some of my more suscepible roses in recent years. I will definitely try this.

SB Susan

    Bookmark   October 18, 2007 at 11:37PM
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pkapeckopickldpepprz(z9 a/b FL)

bumping this thread seeing if Michaelg still sees this as a working solution for Botrytis?

Ceterum, is thios still working for you as well?

Where can one buy Calcium Nitrate, Sulfate or Chloride cheaply in bulk?

    Bookmark   July 5, 2010 at 10:13AM
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pkapeckopickldpepprz(z9 a/b FL)

Any updates I want to try the Calcium Nitrate but don't want to buy a 50# bag if it doesn't work well.

    Bookmark   July 14, 2010 at 2:34PM
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I may have missed something, but there are calcium sprays you can buy - for tomatoes, say, and hydroponics. Are they impractically expensive? Excuse me if this was discussed earlier.

    Bookmark   October 8, 2011 at 2:53PM
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