A close-up of a tomato leaf sprayed with salicylic acid.
A close-up of a tomato leaf sprayed with salicylic acid.

Take two aspirins and call me in the morning.

That age-old advice from doctors may also have relevance to fighting potato purple top phytoplasma, a bacterial infection that has plagued growers in the Columbia River Basin since 2002.

The disease reduces potato yield as well as tuber quality. It is spread by the beet leafhopper, and once plants are infected, there is no known cure.

Carefully timed insecticides can deter the insect's feeding.

Researchers with the Agricultural Research Service based in Beltsville, Md., have conducted trials using tomato plants that they pretreated with salicylic acid, the active ingredient in aspirin. The treatments prevented or reduced the severity of potato purple top, according to a news release.

Tomatoes and potatoes are related and belong to the same botanical family.

The group used two sets of potted tomato seedlings. One set was treated with two salicylic acid treatments—one applied as a spray solution four weeks after the seedlings were planted and a second as a root drench two days before phytoplasma-infected scions were grafted onto the plants' stems.

The second set acted as an untreated control.

The researchers visually rated the plants for disease symptoms as well as analyzing leaf samples for phytoplasma's DNA fingerprint.

In the untreated set, they found the disease in 94 percent of the samples. In the treated set, they found it only 47 percent of the time.

The remaining 53 percent of treated plants were symptom- and pathogen-free 40 days after exposure.

The reason: Salicylic acid triggers a systemic acquired resistance that stimulates plant defenses against invading diseases or other pests.