Common Leaf Diseases and What to do


Leaf disease can occur from time-to-time affecting a number of different plants. They can affect both fruiting plants (like cucumbers, strawberries, watermelon and tomatoes) and also leafy green plants too.


The good thing is that these diseases are relatively easy to spot and if you catch the issue early, you can save your precious fruits and vegetables! The three most common leaf diseases that occur in australia and may affect plants in your airgarden are: Powdery Mildew, Downy Mildew and Rust Fungus. See the table below for more information on what to look for and how to fix it.


Organic Sprays to Control Plant Diseases

For Fungus - powdery mildew, downy mildew and rust


What it Looks Like  

What it Does

Solutions to Fix


Powdery Mildew







  • fungus which spreads a white or ash-grey film over the upper and lower surfaces of the leaves of plants; usually older leaves.
  • powdery mildew fungus favours high humidity and dry conditions.
  • powdery mildew fungi block light to photosynthetic cells, so the plants are weakened in their ability to use light as an energy source.
  • is spread by air movement


  1. Removing the worst affected leaves from the plant may help slow the spread of the disease, plus it will allow for more air circulation.


  1. eco-fungicide from ocp
  • Eco-fungicide is a registered organic fungicide Rapidly kills external fungal growth and spores
  • Effective on a broad range of plants
  • Economical rate (3-4gm per litre)
  • Safe to use on fruits and vegetables
  • No withholding period
  • Safe for beneficial insects
  • Registered Organic (Australian Organic)


Downy Mildew

  • can be identified from the fungal layer on the underside of the leaf
  • develops in moist weather and is accompanied by leaf spots on the top of the leaf.
  • is spread by splashing water.
  • the spots may turn brown or may remain yellow.
  • the entire leaf dies quickly.
  • usually older leaves are affected first, then younger leaves.
  1. Promote good air circulation and leaf drying; use wide spacing between plants.


  1. eco-fungicide from ocp

Rust Fungus

  • small, red or reddish-brown pustules that form on the underside of the leaves
  • fungus destroys the leaf tissue, reducing the plant’s photosynthetic capacity.
  • often results in poor shoot growth or leaf dieback.
  • in extreme cases plants may be killed by rusts
  1. Promote good air circulation and leaf drying; use wide spacing between plants.


  1. eco-fungicide from ocp

A great resource for all pest related diseases in vegetable crops is available from AusVeg. It is an extensive list and has further links for treatment of each issue. Here is the link below:


Remember to always search out solutions that are recognised as having “no withholding periods” meaning, you can spray your fruits and vegetables, rinse and eat on the same day!