Robin Trott
| University of Minnesota Extension
By late July, Minnesota gardens are heavy with ripening fruit. Wet, humid weather has created ideal conditions for fungal and bacterial diseases, and alert growers know it’s time to scout, clean up, and protect the harvest.
From backyard raspberries to small orchards of apples, pears, plums and grapes, problems are multiplying under leafy canopies.
Let’s start in the apple orchard.
Apple scab is a regular late-summer visitor, leaving olive blotches on leaves and dark spots on fruit. If ignored, it can cause early leaf drop and cracked, unsightly apples.Fire blight, more dramatic and often more damaging, scorches apple and pear shoots, leaving them looking burned. Though bacterial in nature, moisture helps it spread, especially in trees that were wounded earlier in the season.
Plums are facing their own midsummer saga.
Black knot is unmistakable, characterized by swollen, black galls that resemble chunks of charred rope. The disease spreads in the spring, but it leaves its mark now.Meanwhile, brown rot appears as a fuzzy, tan mold on ripening fruit, especially after a string of damp days.
Grapes aren’t faring much better.
Black rot turns fruit into hard, shriveled mummies and dots leaves with blotches.Downy mildew creates greasy, yellow patches and fluffy, white growth on the undersides of leaves.As clusters ripen, gray mold (Botrytis) lurks, softening fruit and complicating harvests.
Even the trustyraspberry is feeling the pressure.
Gray mold spreads fast in humid, stagnant conditions, clinging to fruit and foliage.Powdery mildew coats leaves and berries in white fuzz, while late leaf rust dots foliage and fruit with bright yellow spores, rendering berries unfit to eat.Clean up and carry on
So, what’s a gardener to do? Start with good hygiene.
Remove fallen fruit and damaged leaves to break disease cycles.Prune for airflow—dense foliage traps moisture like a sponge.Avoid late-day watering and disinfect tools between plants.Fungicides can help combat persistent threats like apple scab or black rot, but they are most effective when used in conjunction with consistent observation.
Because here’s the quiet truth: healthy fruit doesn’t just happen, it’s watched over. Diseases rarely scream for attention. They slip in softly, tucked beneath a leaf, nestled in the crook of a damp stem, or hiding under a still-ripening raspberry. But gardeners who know what to look for—who take the time to flip a leaf, check the canopy, or question a yellowing spot—are the ones who stay ahead.
In a season like this, with moisture running high and fruit hanging low, vigilance isn’t optional. It’s the difference between a beautiful harvest and a battle with the compost bin. So, walk your garden, notice the small things, and trust that the fruit you save today is worth the extra glance.