Damping-Off Fungicide --- need help!

Please help me. What has been your best fungicide to prevent damping off? I have used Captan which works well for a week or so, but seems to lose effectiveness quickly. I tried 10% Hydrogen Peroxide last year and lost nearly every seedling (the problem with Hydrogen Peroxide is it breaks down too quickly and watering every couple of days is not an option for me). I also tried “No-Damp” sphagnum moss and that did nothing to prevent damping off.

I am open to any suggestions. I cannot take another year like last year where only about 1% of my seedlings survived. Has anyone use Benomyl? Subdue? What concentrations and application intervals? Of course, non-toxic options are preferred, but at this time I am willing to use anything.

Also, is their a preferred growing medium to help suppress the problem?

Thanks for your help!!


Hi Shane,

One thing that I learned from my rose breeding mentor Elton Strack that has helped is putting a spoonful of perlite around the base of the seedling. There are three main organisms that contribute to damping off- species of Rhizotonia, Pythium, and Phytophthora. THe watermolds tend to travel and attack the seedlings at the soil line and the perlite is sterile and interferes with this somewhat. I haven’t used this technique in awhile because it becomes difficult to see which pots need water.

The most helpful tool I’ve had combatting damping off is to plant seedlings into soilless media (Premier Pro Mix, I like it because it is low in bark and I’ve had problems with bark, for instance I learned some Universal mix once had problems because it wasn’t composted enough before being put in the mix and there were pathogen problems). Mineral soil can harbor pathogens easily. Also being very careful to monitor the soil moisture so it is not too wet has been a key for me to avoid damping off. I also try to have good light (seedlings close to lights) to help the plants grow and the soil to dry faster. Usually these things work fine for me, but when I get some sporatic damping off I may try to quickly save a seedling by dipping the stem in captan and rooting it as a small cutting or watering the tray with some captan. I’ve also used hydrogen peroxide as well.



10 % hydrogen peroxide? Commercial drugstore type H2O2 is 3 %. I suggest mixing 5 ml of this 3 % solution with every 95 ml of water that you use including the initial watering. The above recommendation is assuming that one is starting with a sterile potting mix and sterile containers.

Possibly your 10 % H2O2 was killing the seedlings.

I have not noticed that the drugstore H2O2 broke down quickly. The drugstore type contains a preservative. What is the source of your 10 % mixture?

I cannot visualize a healthy system where you would not have to water every couple of days (unless you are doing a closed tissue culture experiment). Has anyone else accomplished such a long between water period time? I have left my system for about a week several times for out of town children / grandchildren visits. I use inverted commercial “pop bottle type” water drippers to supply water during these periods.

I haven’t had problems with damp off since I started letting the surface of the potting mixture dry out between waterings. I let the surface get completely dry before watering. The soil is still damp below the surface where the roots are.

I have had more damping off problems when using a potting mix with a wetting agent. That seemed to keep the entire soil area at about the same moisture level. Without a wetting agent (or maybe just with a different soil mix), the surface would dry while the rest of the soil was still moist. I also spray Triple Action 20 around the stems of seedlings if I start having damping off problems.

Ralph Moore has for years taken the following approach to this problem: The seeds are sown on the surface of a soilless mix in flats. The seeds are simply placed on the surface of the mix. He then covers the seeds with 1/4 inch of fine perlite. Thats all there is to it. Whatever the mechanism might be, it does prevent damping off.

Myself, I use the H2O2 method, and it is much more dependable than Captan if applied regularly. Captan is to be avoided, in my opinion, as it is probably a health hazard.


Thanks everyone. It sounds like Hydrogen Peroxide was not the problem. I will give Hydrogen Peroxide a try again this year. I think the problem may have been that I used rockwool which holds way too much water. For those that use hydrogen peroxide, what growing medium do you use? How often do you water? Do you water the growing medium to saturation?

Paul, thanks for the advice on using perlite.

Thanks again for all your help!




Shane, I use a combination of factors to limit damp-off. One year, I had almost all of my seedlings wiped out. As you know, it is very disheartening.

Now, I use Sunshine Mix #3 to plant the seeds in with a 1/4" top dressing of perlite. I have stopped using Captan, but do still apply a soil drench of Subdue after the perlite is put on. This is all done in a greenhouse.

When I used seed trays under shoplights in the garage, I was very strict about watering the seed trays from below. That also seemed to help a lot.

Jim Sproul

Another old method is to lightly dust the soil with the commercial preparation ‘Gold Bond Foot Powder’.

There is a chemical agent in this preparation that seems to retard damping off.

It isn’t expensive, is easy to apply to the soil and it works.

I do it similar as Ralp Moore does. I learned my method from Wilhem Kordes II in his book