What was it all about?

Control of powdery mildew and leaf blotch in the strawberry nursery and fruit sectors relies on the use of the fungicides myclobutanil and trifloxystrobin. Repeated use of these fungicides increases the risk of the fungus becoming resistant to the chemicals, resulting in them becoming ineffective. Access to a wide range of fungicides with different modes of action is important for managing fungicide resistance across the whole industry.

This project trialled the effectiveness of other fungicides with different modes of action against these fungal diseases.

Results showed that a number of treatments tested by the team were effective against powdery mildew and leaf blotch, including three – bupirimate, cyflufendamid and quinoxyfen – which were granted minor use permits as a result of the work.

To control powdery mildew in nursery runner crops, the research team recommended that growers avoid use of myclobutanil and trifloxystrobin (only apply early in the season if required, based on permit instructions), and rotate the recently permitted fungicides, quinoxyfen, bupirimate and cyflufenamid, through the season.

Nursery growers in Queensland and Victoria later implemented this strategy to minimise the risk of the pathogen developing resistance to myclobutanil and trifloxystrobin in the fruit farms.

Since fluazinam, prochloraz and azoxystrobin + difenoconazole reduced leaf blotch and stem-end rot in strawberry, an application was made for a minor-use permit for fluazinam against leaf blotch in the strawberry nursery sector only.

The researchers concluded that co-ordinating the use of different fungicides between nursery and fruit production farms will extend the effective life of current and new fungicides, and reduce the economic impact of diseases in the strawberry nursery and fruit sectors in the long term.

The concept may also be applied to other horticultural industries with more than one generation of production or propagation, such as potato, to better manage the risk of chemical resistance.