I normally shy away from these topics because, well, people can be a little touchy about spraying things. But I had a few lovely ladies come by last year and request it, so here we go.
How about we call it spritz? We shall flit and spritz amongst the roses.
Brown spots on your plants mean there is a disease present. There are surprisingly few options available for homeowners to deal with fungal problems, and usually they are hidden away in a corner, buried by an entire wall of roundup and pesticides. This makes it hard to even find what you need to deal with the issue, so often folks buy Neem oil or some insecticide that has nothing to do with the problem.
Compounding it further is the fact that by the time you have a disease issue, it’s basically too late. It’s not very satisfying to be out spritzing healthy looking plants.
The first thing to do is think about what time of year it is. By the time late summer rolls around, your babies are all going dormant and will drop their leaves soon, so it’s fairly pointless to spray at that point for superficial issues like powdery mildew. Some of the evergreens may benefit, but it’s best to go with disease resistant varieties with those anyway, especially the larger trees.
For the best (and easiest) protection from common foliage diseases, look for a systemic fungicide. Spritz every couple of weeks starting in spring and go until the flowers are done. Systemic types get absorbed into the plant so you don’t have to apply as often or worry about hitting every part of the plant to give it protection. The one you see most often at the store is called Immunox and works well.
Infuse is another one on Amazon that I haven’t tried. The key is to look for a type that’s systemic. If you have a specific issue you are dealing with, just look for a systemic fungicide that has that issue listed. Some things are hard to diagnose, so the simplest approach is to start early and hope that what you are using takes care of things.
Contact fungicides stick to the surface and don’t get absorbed into the plant. There are numerous different chemicals out there that do that. Copper, mancozeb, and chlorothalonil (Daconil) are all contact fungicides, and can be very effective on their own or in addition to a systemic variety. When using contact fungicides, it’s important to get the undersides of the leaves- easier said than done. They also wash off in the rain.
Here are some trees and shrubs that tend to get the funk at some point in the season:
Hydrangeas-particularly arborescens, macrophylla, and quercifolia.
Dogwoods (powdery mildew, especially the natives)
Hollyhocks -watch out, these get rust like crazy!
We have a lot of disease pressure in the hot and humid Asheville area. To keep your plants looking their best, try using a systemic fungicide like Immunox, starting in the spring, even if the plant looks just fine. This can also be used on tomatoes to protect from blight and extend the season a bit.