Growing green - Fungus among us

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In the past few weeks, I have been inundated with samples of sick and dying plants. For the most part, these plants have suffered from a variety of fungal diseases.

Fungi cause more plant diseases than any other group of plant pests in Minnesota gardens. They attack trees, shrubs, fruits, vegetables and ornamentals throughout the summer. Some common fungi you may find in your garden are:

Leaf spots: One of the most common fungal symptoms is leaf spotting. These can be caused by a variety of different fungal organisms. Usually, leaf spots have a distinct dark brown or red margin. The inner spot is dead, usually brown or black. Outside the margin you will find healthy green leaf tissue. Some common leaf spot diseases include anthracnose, rust, septoria and early blight.

Wilt: This type of fungi can remain in your garden soil for years. It is often spread by improper crop rotation. Wilting symptoms occur in midsummer when air and soil temperatures are high. Leaves infected with fusarium wilt turn yellow, wilt and die. Wilting progresses upward and may first appear only on one side of the plant. Verticillium wilt has the same characteristics as fusarium wilt, but yellowing symptoms are not restricted to one side of the plant.

Mildew: Typical symptoms include a growth of white or gray powder (like talcum powder) on the leaves. It grows in warm climates when nighttime humidity is high and is often seen in areas with limited air circulation.

The good news is that most fungal infections are cosmetic in nature and do not permanently damage plants. Fungal spores are spread by wind, water, soil, animals, tools and other infected plant material.

Prevent infections by using good cultural practices. Avoid crowding plants, purchase disease-free and resistant seeds and plants, water the base of the plant (use drip irrigation, or water early in the day to allow leaves to dry), remove affected plant material and use a thick layer of organic mulch to keep plant material off the ground.

If you have a plant infected by a fungal infection, prevent the spread of the disease by applying a fungicide. Fungicides must be applied early in the season prior to the onset of disease. They do not cure infected plants but protect unaffected plants from getting the disease.

For more information, visit www.extension.

umn.edu.

Until next time, happy gardening!

Tags: country, extension, fungus