Like humans, plants are subject to a broad range of diseases and health conditions. When we notice our beloved plants looking spotty or sickly it can be alarming and concerning, but there are many ways we can intervene and revive them.
While there are a range of chemical ways to treat diseases, they may not always be necessary. With careful and regular monitoring of your garden for early disease outbreaks you can often ‘nip it in the bud’ and achieve great results.
Simple things like ensuring there’s good air circulation between plants and trying alternative remedies like garlic sprays is worthwhile to protect you and the plant. Your garden and all of us will thank you for it later. If you do choose to use any chemical products, please read the label really carefully to be fully aware of what the chemicals are you’re using and what impacts they could have on the environment around the plant and to useful garden insects like spiders.
What causes plant diseases?
Bacteria, fungi, viruses and neglect are the causes of plant diseases, but in Australia we’re relatively lucky compared with other countries which experience much harsher diseases than ours. It's important to have a good understanding of diseases before you can send them packing most effectively and get back to the joy of gardening.
Rust deforms leaves with orange, gold, or brown-red spots and weakens plants. Several fungus species cause rust which is mostly a cosmetic condition. Control is usually not necessary, simply promote healthy growing conditions and plants will overcome a rust outbreak.
Whether caused by bacteria, fungi, or viruses, leaf spots are one of the most common symptoms of disease and something to keep an eye out for on your plants. Other symptoms of disease can include poor growth, rough or curling leaves, deformed fruit or flowers, generally discoloured foliage or sudden wilting.
Bacterial spot symptoms vary, but typically they produced discoloured leaves with dark brown lesions surrounded by a yellow halo. Most common in humid weather or damp conditions, this disease can be controlled by avoiding working among wet plants.
This is a fungal disease which resembles white powder. It appears on foliage and thrives during humid, clear weather. Spacing plants well helps prevent powdery mildew from occurring with the ample allowing for air circulation, discouraging the growth of this disease.
This virus is a nasty one as it’s incurable. Plants such as peonies and others affected by it should be destroyed to prevent the spread of it. Symptoms include yellow or green mottled patterns on leaves. Leaves with the mosaic virus can also be distorted, cupped, or curled.
This fungal disease is most common on roses, causing dark splotches on leaves and leaf drop. Black spot spreads quickly during extended periods of rain. To reduce outbreaks, make sure you have good air circulation around plants for quick drying. When watering plants, do so at the base of the plant too, keeping foliage as dry as possible.
The mighty mite: Rose Rosette
A tiny mite causes this viral disease of rose plants. While it maybe miniscule, it packs a big punch as rose rosette cannot be prevented or cured. Removing infected plants is the best course of action to treat the condition. Symptoms include thick, reddish new stems which typically have many more thorns than normal. Often a large flush of growth appears at the end of infected stems too.
Prevention is better than cure
Prevention is your best defence against plant diseases. It’s important to work with disease-resistant plant varieties and practice good garden hygiene such as well spaced planting and watering at appropriate times of day and noticing changes in your plants and responding quickly. Here’s a basic disease-prevention strategy we recommend:
Quickly identify serious diseased plants which require removal and dispose of them carefully
Position plants far enough apart to allow excellent air circulation
Manage disease-prone plants carefully by growing them in the recommended amount of sun.
Keep plants well-watered, and don't over or under fertilize them
Spray healthy leaves of disease prone plants with a homemade fungicide made by combining 1 teaspoon of baking soda and 1 teaspoon of horticultural oil in about 1 litre of water.