How to spot, prevent and fix these garden funguses

Hike up temperatures and add some summer showers and you’ve got the perfect breeding ground for fungal diseases that can sometimes do extensive damage to trees and plants. We get calls every spring and early summer when people start to see the telltale signs, often with a fair amount of confusion on what exactly is affecting their plant and how to fix it.

So let’s start with the most common summer funguses we see in Central Indiana, including how to spot them and fix them. And remember, you can always bring a sample into the garden center for expert help in diagnosing and treating the problem.

Apple Scab

A fungal infection that attacks apples, crabapples, pear and quince trees. This fungus is not deadly to a plant, but severe infections can cause partial to pervasive leaf drop.

How to spot it

• Brown to olive green spots on young leaves
• Black and slightly raised spots on older leaves
• Severely infected leaves will turn yellow and fall to the ground

How to fix it

Earth Friendly

• Plant disease-resistant varieties whenever possible
• Remove infected leaves and keep fallen debris cleaned up
• Treat with Copper Soap in early spring as soon as leaf buds start to open and every 10-14 days until controlled.
• Treat March through July

Chemical

• Remove infected leaves and keep fallen debris cleaned up
• Treat with Fungonil (topical like a Neosporin to stop infection) or a systemic fungicide like Infuse (a system-wide preventive measure like a flu shot).
• Treat March through July

Fire Blight

A bacterial infection that usually infects a plant through its flowers. Doesn’t seem right, does it? The infection can then spread along branches and do extensive damage to the plant. Susceptible plants include crabapples, apples, pear and hawthorn trees, plus roses and cotoneasters.

How to spot it

• Blackened or ‘burnt’ leaves at the end of a branch
• Tips of young shoots will wilt and curl creating a hook
• Infected leaves and blossoms stay attached to the plant

How to fix it

Earth Friendly

• To prevent infection, apply Copper Soap in spring in 7-10 day intervals as soon as leaf buds start to open and until flowering is done.
• Treat March through May

Chemical

• Once infected, the best thing to do is remove infected branches 10-12” beyond the infected area. Disinfect pruners between each cut with a 10% bleach solution.

Powdery Mildew

Powdery Mildew is a common fungal disease that attacks a wide variety of plants, including lilacs, bee balm, phlox, roses, verbena, sweet peas, crabapples, cosmos, hydrangeas, pansies, oaks and many others. It’s usually not fatal to a plant.

How to spot it

• Powdery splotches of white or gray on the leaves or stem
• Damage can appear on the top and bottom of the leaf

How to fix it

Earth Friendly

• Plant disease-resistant varieties whenever possible
• Improve the airflow around the plant by pruning or deadheading as needed
• To prevent infection, apply Copper Soap in spring through early fall as needed.
• Treat May through September

Chemical

• Treat with Fungonil (topical like a Neosporin to stop infection) or a systemic fungicide like Infuse (a system-wide preventive measure like a flu shot).
• Treat May through September

Tar Spot

A fungal disease that infects maples and Japanese maples in late spring and early summer.

How to spot it

• Light green or yellowish spots early on
• In mid to late summer, yellowish spots develop raised tarlike spots

How to fix it

Earth Friendly

• Remove infected leaves in the fall to lessen the chance of infection the following year

Chemical

• Tar Spot does not require a fungicide treatment because the damage is minor and is not normally present from year to year.

 

For diagnosis of other fungal infections, diseases or insect damage, please call or bring in a sample and/or photo to the garden center for help and advice on what to do next.