A Guide to Disease Control

Maintaining healthy plants isn’t always easy, but keeping diseases at bay is one of the most important things we do as gardeners. Diseases are caused by pathogens that penetrate plant tissue, weaken plants, stunt fruits or flowers, and often result in death. Notoriously tricky to treat, they can have disastrous effects on your garden for many years, so it's vital to know how to identify and prevent common diseases.

Identifying common diseases

Discoloured leaves, wilting foliage, and stunted or deformed growth are all general signs of disease. But each disease will cause unique symptoms too, and we can use these to help identify the problem (Isleib, 2012).

Mildew is caused by fungal spores which thrive in dry soil and humid air. It affects a huge variety of plants, although luckily, is rarely fatal. Mildew diseases are easily identified by the fine chalk-like residue they leave on flowers and foliage (Manhart, 2022).

Mosaic Viruses affect fruits, vegetables, and flowering plants. Highly contagious, they are caused by pests that carry and spread the virus. Symptoms include mottled and curling foliage, stunted growth, disfigured fruits, and poor yields (Song, 2022)

Damping off disease is caused by soil-borne fungi which thrive in waterlogged soil. It usually affects seedlings and young plants, particularly those grown under glass or in high humidity, causing them to rot and die. (Grabowski, 2018)

Rust is a common fungal disease causing small reddish-brown lumps on the underside of leaves. It is caused by a fungal parasite that thrives in mild, moist conditions and weakens the plant by siphoning its nutrients. (O’Neill, 2022)

Treatments

Most diseases are frustratingly difficult to treat. Bacterial and viral diseases are often incurable once they get a foothold, however our The Carbon Garden Program and its intentional design to promote healthy metabolic function in your plants can mitigate the risk of bacterial and viral infection. Additionally, fungicidal treatments can be used on fungal diseases. There are many environmentally friendly fungicides available, or you could make your own. Milk, neem oil, and baking soda are all effective, natural fungicides. Apply regular fungicidal treatments to diseased plants and keep them isolated from other plants wherever possible. (Beckerman, 2008., Klein, 2021)

Mitigate damage by removing and disposing of affected leaves at the first sign of illness, but never put a diseased plant in the compost pile. Good sanitation is key to eliminating the spread of pathogens so sterilise any tools that have come into contact with diseased plants.

Prevention

Proactively preventing diseases by eliminating or limiting harmful pathogens is the most effective form of disease control. Regularly inspect all your plants for signs of illness. Diseased plants treated early are more likely to be salvageable. Rotate your edible plants such as vegetables and fruit every year to disrupt the cycle of species-specific pathogens which can lay dormant in soils for many years. Giving plants plenty of space improves air circulation and eliminates the moist, overcrowded environments that allow pathogens to flourish and spread. When watering, avoid foliage, since wet leaves are a pathogen paradise. Use good quality, well-draining, nutrient-rich soil. Waterlogged soil is a breeding ground for pathogens, whilst a lack of nutrients will weaken plants’ resilience to disease. (Hosack and Miller, 2017., Hoidal, 2021)

Most importantly, ensure your plants’ needs are met. A happy, healthy plant is unlikely to succumb to disease!