It’s that time of year when heat, humidity, and overcrowded foliage can trigger plant diseases. Catching them early makes all the difference! Here are 10 of the most common plant diseases in Michigan right now, how to recognize them, and what products you can use to treat or prevent them.
⚠️ Always Read the Label
Proper application makes all the difference. Always follow product label instructions carefully for best results.
1. Powdery Mildew
What to Look For: White to gray powdery patches on upper leaves, stems, and buds—like a dusting of flour. Starts small and spreads quickly. Infected leaves may yellow, twist, or curl.
Recommended Products:
- Bonide Copper Fungicide
- Bonide Neem Oil
- Ferti-lome Triple Action
2. Early Blight
What to Look For: Dark brown spots with concentric rings (“bullseye”) on lower, older leaves. Often surrounded by yellow halos. Can also cause leathery sunken lesions on fruit and stems. Lower leaves yellow, collapse, and drop.
Recommended Products:
- Bonide Copper Fungicide
- Bonide Tomato & Vegetable Concentrate
- Daconil Fungicide
3. Septoria Leaf Spot
What to Look For: Small, circular gray or brown spots with dark borders on lower leaves. Often leads to yellowing and leaf drop from the bottom up. Look for tiny black specks in the center of spots.
Recommended Products:
- Bonide Copper Fungicide
- Daconil Fungicide
- Bonide Tomato & Vegetable Concentrate
4. Late Blight
What to Look For: Large, dark, water-soaked blotches on leaves, stems, and fruit. White fuzzy mold may appear on leaf undersides in humid weather. Can cause plants to collapse rapidly.
Recommended Products:
- Bonide Copper Fungicide
- Daconil Fungicide
5. Botrytis (Gray Mold)
What to Look For: Tan or brown spots on flowers, leaves, or fruit that develop a fuzzy gray mold. Thrives in humid conditions and often starts on dying plant tissue.
Recommended Products:
- Bonide Fung-onil
- Daconil Fungicide
6. Rust
What to Look For: Tiny, raised orange, yellow, or brown pustules on the undersides of leaves. May cause leaves to yellow and drop early.
Recommended Products:
- Bonide Copper Fungicide
- Bonide Neem Oil
- Ferti-lome Triple Action
- Daconil Fungicide
7. Downy Mildew
What to Look For: Yellow or pale green spots on upper leaf surfaces. Undersides often show fuzzy gray or purple mold. Infected leaves may curl, wilt, or fall off.
Recommended Products:
- Bonide Copper Fungicide
- Bonide Neem Oil
8. Anthracnose
What to Look For: Irregular tan to dark brown blotches on leaves, often near veins. Affected areas may appear papery or scorched. Can also cause sunken dark lesions on stems or fruit.
Recommended Products:
- Daconil Fungicide
- Bonide Copper Fungicide
9. Black Spot (Roses)
What to Look For: Round black spots with fringed edges on rose leaves. Infected leaves yellow and drop prematurely. Typically starts on lower leaves and moves upward.
Recommended Products:
- Bonide Copper Fungicide
- Bonide Rose Rx Systemic Drench
10. Bacterial Leaf Spot
What to Look For: Small, dark, angular water-soaked spots on leaves, often surrounded by yellow halos. Spots may merge, causing leaves to yellow and drop.
Recommended Products:
- Bonide Copper Fungicide
Don’t let plant problems take over your garden—spot the signs early, treat them effectively, and enjoy healthy plants all season long. And remember, we’re always here to help you find the right solution!