Have you stepped outside to find your vegetables or plants unexpectedly struck down by a fungal disease? Don’t worry you’re not alone.
Whether you’re a pro gardeneror simply a beginner, diseases can hit your beloved plants at any moment and a fungal disease is the most common culprit.
“The most common fungal diseases people will see in their back garden is black spot, rust, mildews and root rot, which causes a sudden and inexplicable death of people's beloved plants” says Guy Barter, chief horticulturist at the Royal Horticultural Society.
Keep reading to find out how to spot the different types of fungal diseases in your garden and more importantly, how to prevent them in the future.
How do fungal diseases spread in plants?
“Fungal diseases spread by spores” says Guy. “Funghi have a system of reproduction, which can be either sexual or asexual, and that leads to spores. The spores can be tiny and light, like downy mildew, and spread far and wide in wet weather, or they can be heavy and dense, like powdery mildew, and not spread very far.”
How to treat fungal diseases in plants
Treatment isn’t actually that easy if your plant has a fungal disease. While there are garden fungicides out there, these have to be applied to plants early. The best and most important thing you can do is work on preventing the disease in the first place.
“Only buy healthy plants when you're going to nurseries and garden centers,” says Guy. “Beware of friends bearing gifts, because sometimes they don't quite realise that their plants are infected. Also, if you have one plant that looks off, remove it quickly before it infects the others and finally don't grow the same thing in the same place, so if a tree dies of root rot don't plant another tree or shrub their, plant some bamboo or grass so that you can avoid the problems.”
The most common types of fungal diseases in plants
Black spot
Black spot is when you get black spots on the leaves and stem of your roses. “It starts in spring and then gets worse through the summer,” says Guy.
Treatment: “There's nothing that can be done really. You can apply garden fungicides in the spring, but it's quite expensive; you have to do it from April onwards and you have to do it every fortnight. Even then the disease is often tolerant to the fungicide. If push comes to shove, you either have to put up with it or replant with a rose that is less susceptible. The older ones are highly susceptible, whereas the newer ones are reasonably resistant.”
Powdery mildew
This is a powdery flowery type of mildew that your plant gets on the upper surface of the leaves. “Powdery mildew is usually most common in a normal British summer when it's dry and wet alternatively,” says Guy. “It doesn't spread very far, but it spreads very slowly around the garden.”
Treatment: “Again, you can treat with garden fungicides, but you can also get what we call plant invigorated and mildew preventers, which you spray onto the leaf, it destroys the powdery covering and slows down the spread.”
Downy mildew
This is a fluffy mold that your plant gets on the underside of its leaf. “It only spreads in wet weather, so it’s been quite common this year,” says Guy. “It’s a pesky nuisance for things like grapes, peas and nicotiana, which are tobacco flowers.”
Treatment: “As it's only really a problem in wet weather, if you plant your plants reasonably far apart and prune them so there's good airflow, with luck, downy mildew shouldn't cause too many problems. But if you do get it, I'm afraid the only thing to do is to pull your plant up and start again.”
Rust
This produces rusty spots underneath the leaves of plants. “It’s very common and spectacular, but doesn't do a lot of damage,” says Guy. “Raspberries and plums can suffer from rust and it can affect roses too.”
Treatment: “You can apply fungicides for certain ornamental plants, but usually rusts are not terribly destructive on garden plants and one can put up with.”
Wilt
This is when the leaves on your plant look wilted, but it’s actually not to do with the leaves itself, as Guy says it’s fungus blocking the stems of plants or rotting the root.
Treatment: “The first thing to do is to pull the soil away around the base of the plants and check for any roots going on down there. If there are, then sadly your plant is finished and you'll have to discard it. Next look at the stems. If your stems are wilting you can try pruning out the old stems and looking to see if there's any dark staining in the wood and go on pruning till there's no dark staining, because that staining is a sign that the fungus is doing its evil work. So sometimes you can prune it out but all too often, if it’s already spread through the plant then it'll wilt bit by bit until it's finished so, again, replacing the plant and starting again is required.”
Root rot
This is where your whole plant or half of it unexpectedly dies.
Treatment: “Look down and pull the soil away to see if the roots are rotted. If they are, sadly all you can do is replace the plant in a different place, because the root rot spores will stay in the soil.”
Blight
This disease is very common on potatoes and tomatoes, which destroys the crop and makes it inedible. You’ll notice the leaves of the plant go brown and sometimes crispy.
Treatment: “The best thing is to try and find resistant potatoes and tomatoes,” says Guy. If it does occur in your garden, remove the plant and try to keep the rest of your plants healthy using an organic soil conditioner.
Club root
This is a fungal infection of the root and common in cauliflowers, cabbages, brussel sprouts, swede and turnips.
Treatment: “Club root doesn't like alkaline soils,” says Guy, “so if you put a handful of garden lime in the soil when you're planting that could give a lot of protection. Raising your plants in pots can give a lot of protection and also lining your vegetable garden, so the pH is quite high, at pH seven or over, is an effective way of keeping the disease low.”