Not being able to give a helpful comment on the effectiveness of that specific product, I will point out that for $19.98/bottle (plus tax in most places), and a bottle makes 16 gallons, that's $1.25+/gallon of solution, not economical.

From my past experience with 'organic fungicides,' they usually need frequent applications, especially needing fresh spraying after rains, making spraying, a tiresome task in the first place, even more unpleasant.

I have not yet come upon an organic fungicide that is satisfactorily effective. They are labor intensive, expensive, and fail to do what they claim to do.

Bear in mind, my black spot pressure is severe here in hot, humid, relatively rainy Pittsburgh. In places where black spot is milder, organic fungicides may be a good choice.

Moses

Moses, I don’t spray but If there was, by any chance, an easy, effective, environmentally friendly and inexpensive product out there, I would consider it. 😂

Just what is their criteria for calling something organic, anyway? Why is baking soda anymore organic than a copper based fungicide? Sometimes, I think by calling a compound organic, a company can then jack up the price of their product. Just how can a fungicide "strengthen" a plants immunity. It seems like a bunch of faddish claims. Diane

Diane. I guess I should have looked at the ingredients in this thing. I got a Chicago Peace in a body bag a Costco last weekend. I do believe that rose needs spraying so I plan to try the milk spray. I have a friend that swears by it.

Mas, another old antifungal spray is the Cornell formula of baking soda and some liquid antibacterial soap mixed together in water and put in a plastic spray bottle. I think it was about a teaspoon of soda, a squirt of soap, and a quart of water. No guarantees. I only used it on one rose about 25 years ago. This was The Fairy which had extreme chlorosis from our alkaline soil, which brought a horrible case of powdery mildew. I've never tried the formula on black spot because my roses have never had that. I'd be curious to know your results with the milk spray. Diane

@Diane Brakefield After reading about a huge corporation that fraudulently sold corn and soy as organic when it wasn't, I've just lost all my faith regarding any honesty in marketing. But greenwashing had been chipping away at it for quite some time as it is. At least I know my own garden produce is organic, other than that who really knows.

Diane, thank you for sharing. I think it is with trying. I always have those ingredients handy.

Worth not with

Website for ARBER says its “active ingredients” are comprised of ”95% other ingredients”, and ”Extract of Reynoutria Sachalinensis 5%”. The latter is, interestingly, a knotweed. Which is the weed that is taking over this part of the Northeast. It cannot be stopped. Relentless and destructive.

https://slate.com/technology/2019/05/japanese-knotweed-invasive-plants.html

It looks llke ARBER does NOT identify (at the website) what comprises 95% of its ACTIVE ingredients. I don’t believe this is a misread. Nor does it state what percentage of the product is made up of inactive substances. Particularly unusual since the container says ’concentrate’.

Bottle is a beautiful shade of green. Green always inspires confidence.

The focus is on Powdery mildew, with some mention of downy mildew. Check out the 4th article, if you want to see only one.

I didn’t see anything about diplocarpon rosae, on a quick skimming. None of these are about ARBER specifically, just its one identified active ingredient (knotweed extract).

https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-055809_01-Nov-00.pdf

https://www.nature.com/articles/s41598-020-60148-6

https://www.canr.msu.edu/news/regalia_a_new_fungicide_for_organic_and_conventional_disease_control

https://www.researchgate.net/publication/248843219_An_effective_biofungicide_with_novel_modes_of_action

@rifis (zone 6b-7a NJ) UGH knotweed is determined to survive in my garden no matter what I do. It's a menace for sure.

Well Rifis, if Arber contains a knotweed extract, huge numbers of knotweed were killed to produce the extract, hence the beneficial aspects of Arber. Lots of dead knotweed. The 95% of other ingredients in the active ingredients (gads that's awkward) are baking soda, a bit of antibacterial soap, and lots of water. What do you want to bet? Diane

That’s a good point. Normally, I’d view water to be an inactive ingredient. But in the case of PM, one could consider it to be an ”active” ingredient.

“Dead knotweed”? The growth above ground is barely the tip of the iceberg. Note what England needed to do ( as described in the Slate article, whose link I posted) for the London Olympics.

And, in the same article, don’t miss the comment about the head of civil litigation at a firm in Liverpool.

“His three most profitable lines of work are personal injury suits, bad landlords, and Japanese knotweed”.

Great info, rifis. Thank you for sharing.

Diane, you always make me laugh. 😂

I read how bad knotweed is. I saw the variegated one at a plant nursery (in their display garden) and it look beautiful. I bought it and planted it. As soon as I heard how invasive it was, I dug it up and trashed it. It tries coming back a little the next year but it was easy to eradicate. So maybe the variegated one is less aggressive.

@MasLovesRoses_z8a GA I think variegated plants are just weaker in general so that may have helped you. This whole thread has me wondering if I should plant my kiss-me-over-the-garden-gate seeds... hm.

I wouldn’t lump that one with the evil Japanese knotweed. I grow several different persicarias that are also lumped in with knotweeds but they are very well behaved. Some are ‘too well behaved’ as I do want them to spread. 😂

Oh! Great news then, thanks. I've never met anyone who grows it so I'm glad to hear from you about it.

Here is a link of a garden channel I follow on YouTube. He has a prairie style garden. He has quite the collection of the ‘good’ persicarias.

https://youtu.be/zkZ2A1J3yu4