Damping Off

I have used up my present supply of Captan and before ordering a new fungicide for damping- off, I am open to suggestions on newer products. My hip supply looks very favorable this season and hope to harvest around the middle of October. Thank You

I use a top dressing of perlite and then do a drench with Subdue. This results in very little damp off for me. I stopped using Captan about 3 years ago and haven’t missed it.

Jim Sproul

I plan to use “Serenade” this year. I don’t generally have problems with damping off, but I certainly have lots of powdery mildew and moldy seeds. I tested Serenade last year directly on the seeds and it suppressed many of the molds (not all) quite a bit. It also worked well on powdery mildew without harming the seedlings. Serenade is non-toxic, as well, and is approved for organic gardening. I would think using it for damping-off might (theoretically) yield good results. I hope someone who generally has problems with damping-off will give it a try and report back to us this year.

It appears that if you use Subdue, you should consider yourself a “beta tester” concerning some long term health effects. See:


Please notice that the link above was last updated on March 8, 2006 and yet they still state:

"_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)

Substance Name – Metalaxyl

CASRN – 57837-19-1

Not available at this time.

Back to top

_II. Carcinogenicity Assessment for Lifetime Exposure

Substance Name – Metalaxyl

CASRN – 57837-19-1

This substance/agent has not undergone a complete evaluation and determination under US EPA’s IRIS program for evidence of human carcinogenic potential.

Back to top "

Link: www.epa.gov/iris/subst/0068.htm

I might try Serenade this year if I can find it. I am all for anything non-toxic. I too had read this information regarding Subdue Henry. It’s a little unsettling.

For what it’s worth I began using fish emulsion on my newly sown seed pots and also dosed my up and coming seedlings from last season. The response in growth is amazing.

I am anxious to see how this years new seedlings respond.

Serenade is available on the internet and also at many larger Walmarts.

What dilution do you use of fish emulsion, Robert?

Hi Jude, I’m using about 1 Tablespoon per gallon for now, Alaska brand fish emulsion I found at the local Ace Hardware.

I’m using one of those big metal watering cans. I’m not very exacting in my measurement but I doubt this stuff will burn anything already established. I may go to half a tablespoon per gallon on newly emerging seedlings and alternate with dilute Miracle Gro.

Thanks, Robert. I do use the fish emulsion on my established roses (one “glug” per plant and water it in). I’ll try the diluted 1/2 T/gallon on the seedlings this year. Anyone use any other organics in the seed starting mix?

I have been using 1 tablespoon per gallon of Bonide brand “Fish Emulsion” (2-4-0.5)on “some” of my newly germinated seedlings (when first taken out of the petri dishes and put in seed trays) and on all of my this season seedlings that are planted outdoors in the first year seedling beds.

I say “some” of my newly germinated seedlings as I have been trying a number of different experiments on the excess of (Martin Frobisher X OP) X OP seedlings that have germinated this season.

Even though I have been using a 1 tablespoon per gallon application concentration, I expect that the actual concentration in the seed starting mix will be much lower, as the mix had been pre-wetted. Next, I am planning on a 1 teaspoon per gallon for all of the wettings including the initual.

Robert and Judith, I will look forward to the reports on Serenade and fish emulsion!

I am interested in eliminating damp-off without affecting powdery mildew.

Jim Sproul

We went through this subject many times on this forum.

Just go and search “Damp Off” on this forum and see all the posts over the last two years.

I still wonder what’s all the fuss about damp off ? I never ever had any problems in my 37 years of hybridizing.

I do my seed preparation etc. as I learnd it in Wilhelm Kordes II book “ROSES”.

For more details go to my articles page :

“Rose Rage interviews George Mander” This article covers many tips on hybridizing, raising seedlings etc. and has the most comprehensive information of any article on my site and is ideal reading for the beginning hybridizer. (reproduced by permission)

Link below.

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

Chinosol has been recommended for damping off in the link above. The active ingredient in Chinosol is 8-hydroxyquinoline sulfate. The following link gives a government report on this chemical:


This again appears to be a case of anyone using being a “beta tester”. The following is a quote from the link:

"4. The effects of the substance on human health.

See toxicity information under number 1. Although it is not generally reported as a carcinogen or teratogen, a test of the food additive formerly used as cheese preservative (8-hydroxyquinoline) found tumors in the bladder, brain, and uteri of rats and mice when administered intervaginally (NTP, Peterson, 1978). FDA

We all will do well to protect ourselves from dangerous chemicals. “Beta tester” is an interesting term. I would suspect that it is a term that could be applied to anyone using a chemical product without definitive proof of its safety - that the jury is still out.

This was found on the International Agency for Research on Cancer website regarding HYDROGEN PEROXIDE:

"5.2 Human carcinogenicity data

No adequate data on the carcinogenicity of hydrogen peroxide were available to the Working Group.

5.3 Animal carcinogenicity data

Hydrogen peroxide was tested in mice by oral administration, skin application and subcutaneous administration and in hamsters by topical application to oral mucosa. In mice, adenomas and carcinomas of the duodenum were found following oral administration. The other studies in mice and the study in hamsters were inadequate for evaluation. One study in mice and one study in hamsters showed no promoting activity of hydrogen peroxide.

5.4 Other relevant data

Hydrogen peroxide is formed intracellularly as a result of certain enzymatic reactions. Hydrogen peroxide, either from this source or externally applied, generates hydroxyl radicals that initiate lipid peroxidation chain reactions within exposed cells and can lead to DNA damage and cell death. DNA damage has been demonstrated in bacteria and in cultured mammalian cells. In addition, hydrogen peroxide induced mutations in bacteria, yeast and other fungi and there is some evidence that it can do so in Chinese hamster V79 and mouse lymphoma L5178Y cells at the hprt locus. Chromosomal aberrations and sister chromatid exchanges are induced in both human and other mammalian cells in vitro, but it did not induce chromosomal aberrations in the bone-marrow cells of exposed rats.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of hydrogen peroxide.

There is limited evidence in experimental animals for the carcinogenicity of hydrogen peroxide.

Overall evaluation

Hydrogen peroxide is not classifiable as to its carcinogenicity to humans (Group 3)."

The last line above would suggest that those using Hydrogen Peroxide would also be “beta testers”. It turns out that we all use many products that lack complete safety data.

Jim Sproul

Link: www.inchem.org/documents/iarc/vol71/023-hydrogenper.html

Hydrogen peroxide is an oxidizing agent. Concentrated hydrogen peroxide is not something that I would recommend home users utilizing. The properties of a chemical are often concentration dependent. An example of this is acetic acid. There have often been discussions on garden forumns concerning the safety of acetic acid in dilute and concentrated form.

In addition to concentration, I feel that one should consider the mode of use. Sometimes, after I recommend the use of 5 ml of 3 % hydrogen peroxide per 95 ml of water for watering the growth medium for the use of damping off control, someone will pass on a modified statement that the solution should be sprayed.

I then reply that I do not recommend the spraying of hydrogen peroxide solutions.

When one considers the use of a chemical, one has to consider (among other things) the concentration and mode of use. In other words - is it considered safe when used under specified conditions?

The EPA reports concerning hydrogen peroxide are given below:

Short form:


Long form:


A key word in Jim’s conclusion (“The last line above would suggest that those using Hydrogen Peroxide would also be “beta testers”. It turns out that we all use many products that lack complete safety data.”)

is the use of the word “complete”. I would prefer to use “reasonable” as a criteria. Of course one persons (or groups) conclusion regarding what is sufficient “reasonable” safety data, can be different than another persons (or groups) conclusion.

In summary: I have no problem with the idea that hydrogen peroxide may cause cancer. In fact I would be very surprised if it did not since it is an oxidizing agent. However, I would not expect (based on the reports that I have found) that when used as directed for damping off that it would be a realistic cancer risk. My general criteria for using the term “beta tester” would be as follows: if one is using a chemical in a manner for which “reasonable” safety data are not available.

A compound can itself be dangerous or it can form a dangerous new compound. The 8-hydroxyquinoline sulfate is thought to be a fungicide through the formation of a copper complex. Below is a recent scientific paper concerning this copper complex.

I would like to add to my post about metalaxyl, the active ingredient in Subdue. In case someone thinks that the lack of information about its cancer characteristics are due to no concern that it may have problems in that area.

The following is a peer reviewed scientific article on metalaxyl and cancer:

Title: Biomarkers of effect in evaluating metalaxyl cocarcinogenesis. Selective induction of murine CYP 3A isoform.

Authors: Paolini, Moreno; Mesirca, Renata; Pozzetti, Laura; Sapone, Andrea; Cantelli-Forti, Giorgio.

Authors affiliation: Department of Pharmacology, Biochemical Toxicology Unit, University of Bologna, Via Irnerio 48, Bologna, Italy.

Published in: Mutation Research (1996), 361(2,3), pages 157-164.

Abstract: “The ability of metalaxyl, whose mutagenic/cocarcinogenic activity has as yet not been clarified, to affect specific biomarkers related to non-genotoxic cocarcinogenesis, was investigated. Several CYP-dependent reactions have been studied in liver, kidney and lung microsomes from mice treated i.p. with single (200 or 400 mg/kg) or repeated (200 mg/kg, 3 days) administrations of fungicide. No changes in both abs. and relative liver, kidney and lung wts. were obsd. after metalaxyl treatment. Although a single dose did not affect the considered monooxygenases, a clear example of selective CYP3A induction was recorded in different tissues after repeated treatment. A 3.apprx.-fold increase in CYP3A isoenzymes, probed by N-demethylation of aminopyrine, was obsd. in the liver (both sexes). Again, a 5.apprx.-fold increase (averaged between male and female) in this oxidase activity was present in the kidney. No significant change of the selected biomarkers was obsd. in the lung. A weak, but significant redn. of CYP2B1 isoform in liver (male) was also recorded. Liver and kidney CYP3A overexpression was corroborated by means of Western immunoblotting anal. using rabbit polyclonal antibodies anti-CYP3A1/2. Northern blotting anal. with CYP3A cDNA biotinylated probe showed that, in the liver, the expression of this isoenzyme is regulated at the mRNA level. These data indicate the cotoxic and cocarcinogenic potential of this fungicide.”

cocarcinogenic is defined at: http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=cocarcinogenesis&action=Search+OMD

I would like to point out that metalaxyl has been detected in 10 % of maternal plasma collected at delivery of pregnant urban minority women in a 2003 scientific study. The same study reported that metalaxyl was detected in 18 % of umbilical cord plasma samples collected from the newborns.

The full paper is available free at: http://www.ehponline.org/docs/2003/5768/abstract.html

When I am considering an unfamlar chemical, one of the types of information that I often utilize is whether it is banned in other countries as I feel that our EPA is in general very slow to react to the scientific literature. The following is a list of banned pesticides (relative to those allowed in Canada) as of August 2006.


Please note that both Captan and metalaxyl are listed.

The April 2006 article in the following link highlights 2 important points, 1) that combinations of chemicals can have effects not detected when the chemicals are studied individually and 2) very low concentration exposure over long time periods can have effects not found in short term high concentration studies:


Henry, please don’t misinterpret my last post as a justification or defense for my use of a particular chemical. Also, please don’t misinterpret my statements about hydrogen peroxide to mean that it is a dangerous chemical that should never be used. I was simply pointing out that the “beta tester” label that you used twice in this thread might have a very broad application to even include you.

Though I am sure that you didn’t mean it this way, the term “beta tester” seemed to me a bit insulting. Your opinions and concerns especially about the safety of others is commendable, however, the application of labels that might be considered offensive would perhaps be best avoided. Otherwise, you may find that others will be less willing to share from their experiences.

You mentioned an important point above, “a compound can itself be dangerous or it can form a dangerous new compound.” You also note that “hydrogen peroxide is an oxidizing agent.” In fact it is highly reactive and could itself cause new compounds to be formed when reacting with various household and garden chemicals, the affects of which can only be guessed.

Nevertheless, I think that your recommendation for the use of hydrogen peroxide is a good one. I tried using it myself in a part of my greenhouse, but found it to be too expensive. I will continue to use other effective chemicals being careful to follow the directions for use and safety that are on the label.

Jim Sproul

The statement was made: " In fact it is highly reactive and could itself cause new compounds to be formed when reacting with various household and garden chemicals, the affects of which can only be guessed."

The reactive (oxidative) ability of a solution of hydrogen peroxide depends on its concentration (assuming constant temperature). The actual oxidation potenrial can be calculated from the Nernst equation.

The safety data given in the links below are for 3% and 30% hydrogen peroxide.



As you can see, it is the higher concentrations that are of primary concern regarding the creation of new compounds but one has to use trial and error with lower concentrations to determine which concentration will not affect seedling growth yet will hinder the damping off fungus infection process

The link below gives a very basic example of this type of trial and error experiment: