Your doctor might have given you this advice: "Take an aspirin and call me in the morning." Now, plant doctors may suggest the same.
Aspirin (acetylsalicylic acid) is an Earth-friendly first aid for warding off plant diseases, and may have other benefits. That's Martha McBurney's contention. The master gardener at University of Rhode Island tested aspirin water on tomatoes, cucumbers, beans, basil and other plants.
"It helps boost their immune systems," she explains. Aspirin is an activator of Systemic Acquired Resistance (SAR). When under stress, plants naturally produce salicylic acid, but not fast enough and in sufficient quantities to really help in time. So the bugs get them, and diseases get them, and they show even more stress.
How much, how often
Keep in mind that this is garden-scale – not field-scale. McBurney used was 1.5 uncoated aspirins to 2 gallons of water and added two tablespoons of yucca extract to help the aspirin water stick to the leaves better. A mild liquid soap would do the same, preventing the aspirin water from beading up and rolling off leaves of broccoli and kale leaves. She sprayed the plants every three weeks.
Despite a cool, rainy, damp summer, "the plants were huge, and green and with no insects. We even saw some disease problems that reversed themselves. We think we got a virus on the cucumbers, and they aspirin water seemed to reverse it. The cucumbers ended up being very healthy."
Early this year, USDA/Agricultural Research Service scientists at Beltsville, Md., concurred that the SAR plant response may have commercial potential. ARS Molecular Biologist Yan Zhao is studying how salicylic acid prods plants into releasing their natural defenses against harmful fungi, bacteria and viruses.
Zhao reported evidence that pre-treating tomato plants – a potato relative – with salicylic acid can prevent potato purple top phytoplasma infections from occurring or at least diminish their severity. Salicylic acid seems to offer "relief" to crop plants by priming their defenses.
SAR strategies in the field have had mixed results. It's effective in some crops against certain pathogens, ineffective in other crops or against other pathogens.
Compounds that elicit SAR are very different from conventional pesticides, notes Zhao. ARS has found that many widely planted potato varieties respond to salicylic acid.
So, is this the summer to be doing a little field or garden research trial of your own? Plop an aspirin or two in a gallon of warm soapy water and give it a go.