“Powdery mildew” is actually a catch-all term for several fungal infections that cause similar damage to your plants. Globe Maples are particularly susceptible to what we call “true” powdery mildew. If left unchecked, it can actually kill the entire tree in the worst-case scenario. The good news? If you catch it, you can definitely fight back.
How do you spot powdery mildew on a Globe Maple?
Spotting an infestation is pretty straightforward. You’ll notice fungal spores popping up, especially when the weather gets warm and humid. Here are the tell-tale signs of this disease:
- A white to grayish coating on the leaves
- The residue can be rubbed off with your finger
- It primarily attacks the tops of the leaves
While you can technically wipe the film away, keep in mind that you’re only removing the fruiting body. Wiping it off doesn’t mean the infection is gone!
What’s the best treatment for mildew on your Globe Maple?
If you’ve caught a mild case, a classic DIY home remedy works wonders. A mixture of water and raw milk is a total game-changer for killing off mildew. A quick heads-up, though: you have to use fresh, raw milk. Pasteurized or UHT milk won’t work because it lacks the live microorganisms and lecithin needed to do the job. Mix about 4 cups of water with a 1/2 cup of raw milk and spray it all over the leaves, making sure to hit the undersides too. Repeat this every 3 days until the symptoms disappear.
It also helps to prune back affected branches first. Just be careful—Globe Maples have a heavy sap flow, so pruning before fall can be a bit tricky. However, if the mildew is spreading like wildfire, no home remedy can beat a hard prune back to the healthy wood. Whatever you do, do NOT throw those clippings in your compost pile! The fungus can survive there and hitch a ride back into your garden the next time you fertilize.
Can you prevent powdery mildew on a Globe Maple?
Just like us, plants with “weak immune systems” are much more likely to get sick. If a tree is stressed or poorly maintained, it’s an open invitation for fungi. To keep your Globe Maple in tip-top shape, try these preventative steps:
- Fertilize in the fall
- Thin out the canopy every 2 to 3 years to improve airflow
- Give it plenty of water
- Make sure the soil drains well to avoid standing water
