Cursing leaf disease in garden this year? Here’s the cause, though cure is not so easy

Growing up on a Kansas farm, the weather was a daily topic of discussion. Rain, no rain, hot or dry: The work on the farm depended on the forecast. After I moved away, my sons knew when Grandma and Grandpa Patton called, the conversation always included the weather and the coinciding tasks on the farm.

Even though I am in the city now, the weather is still a daily topic of conversation. Gardeners look at the weather to tend our lawn, flowers and vegetables. While it is not a wheat crop, rainfall is a significant concern as water is the basis for all life.

Rain can either be too much of a good thing or not enough. Feast or famine seems to be the norm. Like farmers, gardeners have to learn to be flexible and take the rain when it comes.

2021 has been a rainfall roller coaster. The rain gauge has swung back and forth between not enough to too much several times this year. Who knows how much will fall in the coming months?

We are all familiar with the phrase: April showers bring May flowers. April showers bring not only colorful blooms but also summer diseases. Wet, warm weather patterns create the perfect conditions for an array of foliage diseases.

In the spring, new leaves have not developed their cuticle or protective covering. Diseases floating in the air can land on the immature leaf and germinate.

As we enjoy the outdoors, the air is jam-packed with billions of disease spores floating through the air, landing on susceptible plant species. We breathe in these spores as we go about our daily lives.

Various fungal spores and bacterial diseases seize the opportunity to grow and develop on the leaf. Leaf spot disease, as the name implies, shows up as a circular lesion. Depending on the species, the colors can range from black to brown or even bright orange. There is usually a darker ring around the outside of the spot.

Affected leaves can have just a few spots or in some cases can be covered. It seems like just about every plant species has some type of foliar leaf disease.

Common leaf spot diseases can appear on apples, crabapples, pears, dogwoods, hydrangeas and many more. Each plant species is affected by a different species of the disease. They are grouped together based on symptoms. Rust is common, creating rusty-orange lesions on apples, crabapples and pears.

Leaf spots are a mixed bag. Early defoliation is the most likely symptom that causes concern. Treating the plant for various leaf spot diseases is usually not recommended. It requires repeated applications of a fungicide. Treatments are often ineffective as the leaf continues to develop and rain washes off the application, requiring another treatment.

Like the weather, there is not much a gardener can do. Leaf diseases are rarely life threatening. They just look bad, causing us to stress. If we could only control the weather, we would have one less problem. Now that’s wishful thinking.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Have a question for him or other university extension experts? Email them to garden.help@jocogov.org.