If you grow mangoes in Florida, two diseases will cost you more fruit than anything else: anthracnose and powdery mildew. Both attack the flowers and young fruit, and both are driven by weather. You can't control the weather, but with the right variety, a little pruning and well-timed sprays, you can tip the odds back in your favor.
Anthracnose: the rainy-weather disease
Anthracnose is caused by a fungus in the genus Colletotrichum. It thrives in warm, wet, humid conditions, which is exactly what South Florida delivers much of the year. The spores spread by splashing rain and heavy dew, so a wet bloom season can be devastating.
What it looks like:
- Flowers: dark spots on flower panicles that spread until the flowers blacken and die. This is often called blossom blight.
- Young leaves: irregular dark brown or black spots, sometimes with holes as the dead tissue falls out.
- Young fruit: black spots that cause small fruit to drop.
- Mature fruit: dark, sunken spots, sometimes in a "tear-stain" pattern running down the skin, that turn into soft rot as the fruit ripens.
Powdery mildew: the dry-weather disease
Powdery mildew is a different fungus that shows up as a white or grayish dusty coating on flower panicles, young leaves and tiny fruit. It tends to appear during the cooler, drier weeks of our winter and early spring, often when nights are cool and humid. Infected flowers dry up and drop, and infected young fruit may fall or develop scarred skin.
Because mangoes bloom in winter and spring, your trees can face both diseases in the same season: mildew during the cool, dry spells and anthracnose when the rain returns.
Step 1: Choose a more tolerant variety
Varieties differ a lot in how they handle disease. Some, such as Tommy Atkins, are widely known for tolerating anthracnose better than many others, which is one reason it has been planted so widely. When you're choosing a new tree, ask about disease tolerance, not just flavor. Our grafted mango trees collection includes several varieties, and our comparison of Carrie, Pickering and Valencia Pride can help you narrow it down.
Step 2: Open up the canopy
A dense, crowded mango canopy stays wet long after rain and dew. Pruning to let in light and air helps leaves and flowers dry faster, which makes life harder for fungi. It also makes spraying more effective, because sprays can reach the inside of the tree. Time it right: prune after harvest, by midsummer, so you don't cut off next year's flowers. Our guide to pruning mango trees after harvest walks through it, or our Tree Pruning Service can do it for you in Miami-Dade.
Step 3: Clean up
Remove dead twigs, old dried panicles and mummified fruit from the tree, and rake up fallen fruit and leaves. These are where the fungi survive and multiply between seasons. Bag the debris rather than composting it near the tree.
Step 4: Protect the bloom with well-timed sprays
For backyard mangoes, protective fungicides are the main tool. The key word is protective: these products prevent infection on healthy tissue, but they can't revive flowers that are already black.
- Copper fungicides are commonly used on home mangoes for anthracnose. Sprays usually start when flower buds begin to swell and continue at the interval on the label through fruit set, especially during wet weather.
- Sulfur is a traditional option for powdery mildew. Check the label for temperature limits, since sulfur can damage plants when applied in hot weather.
Always read and follow the product label for rates, timing, pre-harvest intervals and safety gear. The label is the law, and it's there to protect you, your tree and the pollinators visiting it.
Step 5: Handle fruit with care
Anthracnose often hides on fruit that looked clean on the tree, then shows up as dark spots during ripening. Harvest when fruit is mature, handle it gently and ripen it at room temperature. Eat or process fruit soon after it ripens. Small spots that are only skin-deep can be trimmed away. Fruit with soft, spreading rot should be tossed.
Is it really anthracnose?
Black flowers and spotted leaves can also come from cold damage, insect feeding, sooty mold or nutrient problems. If you aren't sure, or if sprays haven't helped, it's worth getting an expert opinion before spending more on products. Our article on why mango trees don't fruit covers other common causes.
Let's protect next season's crop
I'm Tony, a botanist and arborist, and I run Giardino Fresco with my family in Miami. Fall is the perfect time to plan, before the bloom starts. With our Sick Tree Diagnosis Visit, I'll check your mango anywhere in Miami-Dade for disease, pests, nutrition and watering issues, and leave a written care plan with clear next steps.
Ready for a better mango season? Book your diagnosis visit and call or text 786-774-2125 to schedule, or shop our grafted mango trees.
