I like to read articles that are layed out in simple terms. This made no sense to me as a newbie. LOL. Sorry Henry!

Henry, would you kindly translate a 3 mM solution of H2O2 into drugstore peroxide per gallon?

This Emma Gachomo, a Kenyan woman, has become the leading blackspot researcher in the world.

I don't know whether Kenya vs. Germany is enough to generalize into tropical blackspot being more virulent than temperate-zone blackspot. I guess the hunch would be that not having to preserve itself through winter would allow the tropical blackspot more latitude to evolve in other ways. But for those who didn't read the article, one finding was that, after inoculation with spores, strains from Kenya attacked and killed the rose leaf faster than strains from Germany.

The other (and perhaps more interesting) finding was that pre-treatment with hydrogen peroxide stiffened the leaf's resistance against blackspot. Caution: too much peroxide can burn foliage severely. We have no idea how often it would need to be applied to be of any practical use.

Thanks for translating michealg! I'm still in the books for dummies stage. LOL

Dr. Gachomo's PhD is on line. She earned it in Germany with support of the German Government to try to strengthen the Kenyan cut flower market for roses.

I know some scientists at the University of Tennessee are trying to apply what she started to some of the races of Black Spot on our continent.

That's interesting! Is humidity also accounted for? I try to get the full article if I can.

"Henry, would you kindly translate a 3 mM solution of H2O2 into drugstore peroxide per gallon?"

H2O2 has a molecular weight of 34.

3 mM is .003 moles per liter of solution which is 0.1 grams per liter (.003 X 34).
Drug store H2O2 is 3 % H2O2 (by weight, see http://www.sciencelab.com/xMSDS-Hydrogen_Peroxide_3_-9924298). This is 30 grams per liter or .03 gms per ml.

So one would take 3.3 ml of drugstore H2O2 and dilute it to a final volumn of 1000 ml to get 0.10 gm per liter (which is a final concentration of 3 mM).

Since 1 gallon is 3.78 liters, you would add 12.5 ml of the drugstore 3 % H2O2 (3.3 times 3.78) to enough water to fill a gallon container to make your working solution.

For my rose seedling damping off prevention, I use 5 ml of 3 % H2O2 to 95 ml of water. As can be seen, I use a much higher concentration than they utilize.

I hope someone checks the calculation as it has been a long time (I retired in 93) since I have done much of this.

Thank you, Henry. So that would be 2-1/2 TSP (or 1 TB might be OK) of drugstore peroxide per gallon-- as a foliar spray to encourage disease resistance. Peroxide can also kill spores, but I don't know if this concentration would be strong enough.

Interesting! Has anyone on the forum actually tried this?

Oh, and thank you Henry.