If anybody wants to try, remember that aspirin can burn foliage. I have read that about 2/3 of a standard tablet dissolved in a gallon (or was it a quart :) does not burn if you take normal precautions. The writer thought that it reduced blackspot, but she didn't have a good experimental setup, which requires control plants of the same varieties.

This is one popular press article with concentrations.

http://www.plantea.com/plant-aspirin.htm
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A Google search will give you many more.
https://www.google.com/?gws_rd=ssl#q=aspirin+plants
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Here is a previous aspirin thread in this forum.

http://forums2.gardenweb.com/forums/load/roses/msg1011110221766.html

Here is a link that might be useful: link to first article

I've heard about this for years but never tried it. Maybe I'll do some experimenting with it and see what results I get.

Do you have to spray it, or can you also just apply it to the soil? thanks,bart

Bart, I did a quick Google search and found this:

"2 Uncoated Aspirin.......pushed 2" into soil on opposite sides of plant*"

"AspirinâÂÂs ingredient, salicylic acid, has been found by the University of Florida and USDA researchers to activate and boost a plantâÂÂs SAR (Systemic Acquired Resistance) against bacterial, fungal and viral diseases. When sprayed with the aspirin/water mixture (1 ý aspirins to 2 gallons of water mixed with 2 tablespoons of a surfactant such as mild soap or anti-transpirant) every 3 weeks, it not only improved the plantâÂÂs resistance to disease, but also improved growth, increased fruit size and production. Tomato expert Steve Goto found that putting the aspirin directly in the soil next to the plant is also an effective way to increase the SAR."

http://www.gardenlife.com/store/information/tips
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Myself, I would like to see a controlled experiment concerning the soil application before recommending it. Maybe it could be used as a school science project.

Here is a link that might be useful: link for above

Thank you, Henry. I may try it...though please don't expect me to do it in a controlled, scientific manner,lol! That's really not my thing at all...
I like the idea of trying the soil application,for several reasons. Mainly, because I want to switch over to a no-spray garden, which means "don't spray ANYTHING". Apart from environmental/health reasons,it's also getting to be just too impractical. My garden keeps getting bigger; it's on a steep slope, and faces South-west. It's in the woods, with no electricity or other unnatural light source and far from my home as well,so here under the blistering sun of Italy, this means that spraying the whole thing requires efforts ever more Herculean,and I'm just beginning to think it's totally not worth it. But sticking stuff in the ground is a different story: no need to worry about burning the foliage,etc.thanks for your help,once again! bart