Fact sheet: Managing weather induced fungal staining (saprophyte damage) in oaten hay windrows

Managing weather induced fungal staining, also known as saprophyte damage, is important for protecting the quality and value of oaten hay.

Saprophyte damage develops when common fungi grow on the sun-bleached outer layer of hay windrows during curing.

Rain, heavy dew, high humidity and long periods of wet weather increase the risk. While saprophyte damage does not affect the feed value of hay, it can cause dark staining and poor appearance. This may lead to export market downgrades or rejection.

The highest risk occurs between cutting and baling, especially when windrows stay wet for long periods. Heavy rainfall, slow drying conditions, dense windrows and high-yielding crops all increase the chance of fungal staining.

Growers can reduce risk by avoiding cutting before forecast rain, cutting only when crops are dry, and aiming for fast curing and timely baling. Lower windrow density, conditioners and tedding may also help hay dry faster.

No fungicides are registered specifically for saprophyte damage. However, some fungicides used to manage oat diseases can reduce fungal staining in some seasons. Growers should always follow label instructions, withholding periods and export residue requirements.