I hate it when I have to tell a gardener that they have to yank out a plant because of an incurable disease. It’s even worse when it’s your brother.
Such was the case last week when I was visiting his garden in Poulsbo. They moved to this house a couple of years ago and inherited a long-neglected garden including some beautiful dahlias.
He was concerned about one stunning apricot orange double that had developed a yellow green mottling on its leaves. The local nursery told him it was a mineral deficiency and to treat it with Epsom salts and magnesium salts.
That didn’t help and for good reason. Nutrient deficiencies usually show up as stripes along leaf veins and odd leaf colorations. This was a mottled green and yellow with no pattern to it. I was pretty sure it was a disease but to be certain I tucked a few leaves in a sandwich bag and brought them home to our WSU Master Gardener Plant Clinic. It only took them a few minutes to identify the discoloration as dahlia mosaic virus.
That was the sad part because I had to tell him that there is no cure, and he had to pull them out to keep it from spreading to his other plants. Needless to say, they were really disappointed. The only thing he could do was treat the plants around it for aphids using insecticidal soap to prevent the spread of the disease. Aphids are the carrier of the virus.
This story illustrates how important it is to get good advice and a correct diagnosis before you start wasting your money or putting your garden at risk. Locally, our best resource is the WSU Master Gardener Program located at the WSU Spokane County Extension Office. Volunteers in the program receive more than 100 hours of science-based horticulture education, including training on how to identify and treat a wide variety of diseases and insect issues.
The Master Gardener Plant Clinic at the Extension Office is staffed six days a week and services are free.
The information staffers use is drawn from research done at WSU and other universities, which means the information has withstood repeated verification. The philosophy of the Master Gardeners is to present a range of treatments (if available) including verified organic solutions, suggesting the least harmful to the environment first. Solutions can include changing your gardening practices, making sure the plants are receiving the proper fertilization and water, using benign chemicals such as insecticidal soap, or allowing predator insects to control problem insects. Only when other suggestions have failed, or the problem is severe, will they suggest using a strong chemical.
To get a garden problem identified, bring fresh samples of leaves, stems or sod to the WSU county plant clinic. The samples should be in plastic bags to keep them from wilting. Bring in good pictures of the area around the plant in question.
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