DISEASE

NAME
Rust in Pelargonium
Puccinia pelargonii zonalis


Description
A fungal problem specific to the Pelargonium group.

Symptoms
The appearance of pale green spots on the upper leaf surface is followed by pustules on the leaf underside corresponding with the spots and realising reddish brown spores. As the infection increases the leaf becomes yellow except the enlarged greenish spots and fruiting pustules form a secondary ring releasing more spores. The leaf may fall prematurely and the plant looses vigour.

     

Source and Dispersal
The spores are found on infected plants, fallen leaves and discarded plant cuttings. It is dispersed by wind and infected plants.

Favoured Conditions
It prefers a warm humid climate and infects new growth during spring.
     
Affected Plants
Zonal pelargoniums are the normal host. Regal pelargonium and ivy leaf pelargoniums are not normally attacked.

     

Non-chemical Control
Remove infected leaves or plants and destroy. Avoid high nitrogen fertilising on infected plants as this produces soft new growth that is venerable to attack. When planting select an open sunny position with good air circulation and avoid wetting the leaves or overwatering.

Chemical Control
Spraying during optimum conditions with a preventative or contact fungicide such as zineb or wettable sulphur.