Remove any infected leaves immediately. However, be careful not to remove too many, as removing them in large numbers is likely to do more harm than good. It is important to move the fallen leaves before they start to decompose. As is the case with many garden diseases, do not compost infected plants.
The plant rust spores spread through the air, so separate infected plants from healthy ones to avoid cross contamination. Water in the early morning to allow the plants to have a chance to dry out during the day. Water plants from the base, as watering from overhead will cause the spores to be carried back up to the plant by splashing water.
Prevent rust on plants by keeping greenhouses well ventilated and by pruning and thinning plants. Finally, you can use a sulphur-based fungicide but always check the manufacturer’s recommendations for use.