Florida’s rainy season is just starting. That means being watchful of potential fungus and bacterial infections in the garden. Heavy rain amounts may cut down on your irrigation bill, but they also can cause a lot of issues, and wash away mulch and soil.
A few rainy days in a row may combine with our humidity and high temperatures to create the ideal environment for fungus and bacterial issues in the garden. During the hurricane months — June to November — Florida may experience daily rain and sometimes heavy downpours.
Hunting Fungus in the Garden
First, begin looking for the early warning signs — spots on leaves, discoloration of leaves, wilting of stems. There are plants more susceptible to fungus and disease, which can help you diagnose an infection early. Don’t be fooled; sturdier plants may appear unaffected but are possibly exposed to the fungus. Once a fungus issue is identified, it’s time to implement treatment. Treat all nearby plants.
Plants that make it easy to spot infections include:
- Roses are notorious for quickly developing blackspot on leaves.
- Hydrangea, begonias, dahlias, roses, and other ornamentals may show powdery mildew.
- Fruit trees and tropicals may start to display rust fungus.
- Turfgrasses that are susceptible to leaf spot and take-all root rot.
Florida’s Common Fungi
If all plant fungi looked the same we could easily identify plants that were infected and control would be simple. In fact, some fungi are beneficial and perform an essential role in decomposition and nutrient recycling. Composting depends on healthy fungi.
Powdery Mildew 
Leaf Spot 
Rust Fungus 
Brown Patch Fungus
Vegetables, Ornamentals, and Trees
- Powdery Mildew attacks a wide variety of plant types. This fungus attacks the leaves and flowers of plants with white spots that can completely envelop the surface of the leaves and flowers with a white, pasty film. Leaves and flowers begin to succumb to the fungus, and without treatment, the plant could die.
- Leaf Spot is also easy to identify. Spots may be raised or flat on the surface. Sometimes a small halo effect will appear around the spot as the disease pulls nutrients from the leaves. Spots grow larger as the disease matures until they are the size of a pea or even bigger. Then leaves will turn yellow, then brown, and ultimately fall to the ground. Leaf spot spreads through the air and overhead watering.
- Rust disease takes over a plant quickly and displays orange-colored spots on the tops and bottom of leaves. Rust typically will not hurt the plant on its own. But it can cripple its ability to photosynthesize nutrients and weaken its growth.
- Crown or Root Rot attacks large and small plants in the landscape. This fungus attacks at the root or structure of the plant, often spreading undetected until it’s too late. Because root rot attacks the root structure, early detection displays at the new growth. A professional is the best resource to treat this fungus. Look for a general wilting or failing of new growth. If your plant fails due to root rot, do not replant the same species in the same location. The new plant will probably die as well.
Lawn Diseases
- Brown Patch attacks lawns when the humidity is high. Watering at night or having a layer of dead grass in the lawn can cause fungal disease that will kill the turf. Most of the time, it will start in one area of the lawn and quickly spread. Lawn fungicide treatments are typically granular and can be applied via a spreader.
Treating a fungus outbreak
Treating a fungus outbreak successfully hinges on the severity of the infection. A handheld pump sprayer works best for applying any treatment. Like with people, the earlier the problem is diagnosed, the better the chance for a cure.
Recipe for a homemade fungicide
3 teaspoon of baking soda
1 teaspoon vegetable oil (you can use Neem Oil)
1/2 teaspoon Eco-Friendly dish soap
1 cup of water
Combined all ingredients in a spray bottle. Shake well before applying to plants.
You could choose a commercial fungicide applied via a spray bottle or pump sprayer. There are several brands available at the local garden center or via Amazon or Walmart. Be sure to mix them according to directions and again, apply to the exposed leaves and stems of the infected plant.
I’m a gardener who likes to keep as few chemicals around as possible. I like Bonide Infuse Systemic Disease Control Concentrate for general fungus management. At around $17 a bottle, it’s a good product to have on hand.
Daconil is another highly reliable product for treating more than 80 diseases on vegetables, flowers, shrubs, and trees.
Most fungicide products are applied using a pump sprayer. I prefer the 1-gallon or 2-gallon wanded pump sprayer. It will last years with the right care. You can apply treatment exactly where you need it.
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