Fungicide findings for damping-off

General Discussion
1

Over the past few years I have had terrible problems with damping off. Last year I lost everything. This year I tested several methods of control.

I grow my seedlings under lights (16 hours on, 8 hours off) in a basement. The temperature varies from 45 - 65 degrees. I used a sterile medium, Horticubes, for the experiment. My tap water appears to be packed full of fungal spores, so just watering innoculates the medium. I suspect the culprit to my problems is some form of Pythium.

What I used:

Hydrogen Peroxide – .15% (5% of the 3% store-bought variety) at every watering, generally once a week.

Captan – 1 tbs per gallon every 2 - 3 weeks.

Benomyl – 2 tbs per gallon every 2 - 3 weeks.

Banrot – 1/2 tsp per gallon every 3 weeks.

Here are my findings:

Hydrogen Peroxide, Captan and Benomyl were completely ineffective. 100% of the these seedlings suffered from root rot and/or stem rot. Only those that germinated within 2 weeks survived (before the fungus could take hold). Any seeds that germinated after 4 weeks, died within days.

Banrot on the other hand, was completely effective. No stem or root rot was apparent. Some of the leaves of the seedlings did yellow, but the seedlings survived. To see if Banrot worked in curing damping off as well as preventing it, I applied it to several flats where damping off/root rot was already widespread. It worked perfectly. Roots that had almost completely rotted, were quickly replaced with new, white, healthy roots. It even saved a few seedlings that I thought were lost.

Since others have used Hydrogen Peroxide with success, I suspect it works if better conditions are provided. Horticubes hold way too much water and my basement has minimal air circulation, despite a small fan. I also suspect, that certain varieties of fungus are less affected by hydrogen peroxide.

Since Banrot contains two probable carcinogens, I would like to use it only when absolutely necessary. Next year I will use a better draining medium and buy a bigger fan. I want to try SoilGard and/or RootShield. It is nice to know, however, that there is something that works in case these other methods fail.

Anyway, hope that helps someone. Just remember, what works for my fungus problems, may not work for yours. Also, if you use Banrot, be VERY careful.

2

I wonder if your once a week watering is the problem. I water every 2 to 3 days. If I tried to add enough water for a week, the soil would be saturated.

3

Hi Henry. I should have pointed out that, for this test, I saturated the medium every week on purpose to see what worked under overly wet conditions. With better airflow, lighter and more frequent waterings, and a better draining growing medium, I think the results would have been different.

Henry, thanks for all your pointers and help.

4

Thanks for doing the experiment and communicating your results with us Shane. There are three main genera that cause damping off- Pythium, Rhizoctonia (may not be spelled exactly right), and Phythophora. Banrot is effective against all three, but the other standard fungicides are only effective against two of the three. Your results may reflect the organisms you had as well. In any case your results highlight that Banrot is an effective choice.

David

5

I have been hybridizing roses for about 35 years now and raised about 15 to 20 thousand seedlings over the years.

Never ever did I have problems with damp-off. I may have lost one in a hundred at times.

The only seed-parent which gave me

6

Sorry, “Rose Rage interviews George Mander”…

is not on my Articles-Page, but on my links-page.

This article covers many tips on hybridizing, raising seedlings etc. and has the most comprehensive information of any article on this site and is ideal reading for the beginning hybridizer.

Link below.

Link: www3.telus.net/georgemander/articles/roserage.html

7

“Rose Rage interviews George Mander”… now on Articles-Page, and back where it belongs.

My son who is maintaining and updating my site has just changed the link.

You may have to Refresh or Reload if you have been on my site before.

Link: www3.telus.net/georgemander

8

Extract from “Rose Rage interviews George Mander”

How do you prepare your seeds prior to stratification and planting?

I extract the seeds right away and soak them in a disinfectant solution (for 1hr) before I store them temporarily in moist paper towels in the fridge at approximately 40 degrees F.

Usually within 4 to 5 weeks all seeds are harvested. I will then soak the seeds again in this special solution for about 2 hours prior to planting them into 2" high seeds trays. The disinfectant that I use was recommended by the late Wilhelm Kordes in his book Roses. The name of the product is ‘CHINOSOL’ and it comes in water soluble tablets. I get it from Germany and the active ingredients are 8-Hydroxychinolinsulfate and Kaliumsulfate.

Wilhem Kordes also recommends using 1/4" to 3/8" layer of sand on top of the seed trays in order to cut down on the damp off of the seedlings and also to keep moss from growing on the surface of the seed trays. I also put a layer of sand on top of where I plant my germinated seedlings. I am currently using a professional planting mix called SUNSHINE MIX #4 for germinating my seeds and for planting the seedlings within a day of their germination. All these things combined have cut my damp off losses down to zero with most seed parents, and with certain seed parents I may have only 1-3% losses.

Link: www3.telus.net/georgemander/articles/roserage.html

9

If you can explain how the sand on the surface prevents damping off fungus below the surface then I’ll accept it, but I believe you’ll find that the sand on top is actually to the keep the fungus gnats at bay … an old standard technique for cuttings. One might attribute fungus gnats to damping off fungus but they are different organism at work here. Excuse my butting in …

10

Im not sure what the fuss is about. With good air circulation and a cover medium (I use really fine perlite since it is sterile and cheap) I get maybe 3/1000 damp offs.

11

Jadae, does that stop the fungus gnats as well as the sand? I’ve never had damping off problems but I sure have problems with those ^&*() fungus gnats!!! GRRRRRRRRRRR!

George, how exactly do you use the sand? Is the germinated seed planted on the soil and then covered with the sand (up to the cotyledons) or is the germinated seed planted on the sand with the root in the sand?

12

No but coconut coir instead of peat moss is supposed to. I didnt get any at least. As a lesson from others, careful selection of coir is required.

13

Judith Singer wanted to know :

“how exactly do I use the sand?”

My seeds are put on the top of the the # 4 mix I am using and then I push them lightly into the planting mix with a spoon. Then I put a 3/8 to 1/2 " layer of clean sand on top.

I wonder myself what ALL the fuss about damp off is, as I never had any problems in 36 years of hybridizing.

It’ the disinfecting of seeds, the sand on top and the # 4 mix which ALL work together. Read my post above about what Wilhelm Kordes writes in his book.

By the way, I had no mentor at all when I started in 1969 and learned EVERY thing from the Kordes book.

Good luck to ALL next spring.

14

George,

Thank you so much for sharing your information on preventing damping off. I have one question. What do you mean by clean sand? Are you disinfecting the sand? If so, how?

Thanks,

Shane

15

Hello Shane,

Sorry it took so long to reply as I never have much time in the summer.

You had asked :

" What do you mean by clean sand? Are you disinfecting the sand? If so, how? "

I am getting the sand from a river bank nearby. Then I screen it through a fine 1/16 mesh. When I started over 35 years ago I used to bake the sand in the oven at 350 F. for about 1 hr.

After a few years some hybridizer friends told to try without baking as it was washed very clean already. At one time I got some sand from a building supply place but it looked dirty to me and I never used it.

I have been using the river sand without baking for about 25 years now and it works just as well.

I hope this info helps.

George

Link: www3.telus.net/georgemander/

16

Thanks George, that does help a lot.