Fungicides work by stopping or inhibiting fungal growth, sporulation or germination of spores. Different fungicides act on different stages of the fungal lifecycle and not all fungicides are effective against all fungi. Fungicides can be categorised into different groups including those that are protectant, curative, eradicant, contact and systemic. These terms provide an indication as to how the product will act and are important for their effective use.
Resistance occurs when a pathogen that was once sensitive to a fungicide is no longer sensitive (not controlled). There are many ways to manage fungicide resistance including using cultural practices to reduce fungal populations, applying appropriate products only when they are necessary, applying to hot spots and applying protectant products leading up to high risk periods.
All of the above topics are discussed in more detail in the factsheet on Fungicides, Resistance and their Management in Production Nurseries. It includes details on the mode of action of fungicides, product movement in plants and actions that reduce the risk of causing fungicide resistance.
Figure caption: Alstroemeria with a severe infestation of anthracnose (Colletotrichum) causing leaf spots and blight.