Fungal Problems

By: Jennifer LaMontagne – Horticulturist – Bloch’s Farm – Green Lake, WI

As you’ve been checking your outdoor plants for pests and diseases, have you noticed spots on the leaves of your trees, shrubs, or perennials? Have they been looking less than vigorous no matter what you try? A rainy, humid summer can lead to problems with fungus. Fungus occurs naturally in the soil, and many kinds are actually beneficial for the earth by decomposing dead plant matter into simpler chemicals. However, there are types of fungus that can invade and cause ill health in our plants. 

Fungal infections are usually most severe during moist, mild weather. Look for leaves that are curling, turning yellow, or prematurely dropping. Keep an eye out for circular spots on the leaves of your plants. Typically small in size, up to ¾ inch in diameter, they can appear in a wide range of colors from yellows and reds to browns and blacks. While many spots will have a definitive margin, they can also join together to form blotches. 

Fungal diseases spread in several ways. Fungi that live in the soil and attack plant roots are most commonly spread when soil or infected plants are moved from one place to another. These types of fungi are responsible for root and crown rots in many species. Other fungi depend on splashing water to spread their spores. Many of the fungi that cause leaf spots on trees and shrubs spend the winter as spores on bark or on fallen leaves. They are then washed onto new leaves during the spring rains. Another common way fungi are spread is by dust-like spores that are carried to other plants by wind, insects, animals, plant contact, and tools. These types of fungi are responsible for serious diseases such as oak wilt, Dutch elm disease, and fire blight.

It is important to identify and treat fungal diseases as early as possible. Using fungicides early on may be helpful as they often work best as a preventative rather than as a curative measure. While you may not be able to completely remove harmful fungus from your soil, you can reduce the negative effects by making a few changes in your gardening techniques. Start by removing affected plants. At the end of the season, remove all plant debris from your beds. Refrain from placing affected plants or debris in your compost area. Plant a variety of crops in different locations each year or consider allowing the land to lie fallow for a while. Choose plant specimens that are resistant to soil-borne diseases. 

 Bloch’s Farm is open 7 days a week: 8 am to 5 pm Monday – Saturday and 10 am to 4 pm Sunday. We carry a variety of fungicide products to safely treat your plants. Available brands include Copper Fungicide, Biosafe Disease Control, Natria, Neem Oil, and others. 

              Check out our huge selection of trees, shrubs, and perennials too! Stop in today and our knowledgeable staff will be happy to help you. Feel free to call 920-294-6000 or e-mail with any questions. Visit our website online at and follow us on Facebook and Instagram. Join us for this weekend’s sale! August 27th – August 29th: 25% Off Select Garden Decor!

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