Sugar beet growers should look out for alternaria after reports that some commercial crops have developed yellow foliage this autumn.

The British Beet Research Organisation (BBRO) said that yellowing was appearing most in crops that have not received a fungicide spray or only one spray. For crops sprayed just once, the oldest and newest leaves often appeared least affected.

“While this phenomenon appears to be variety related, the exact cause is not understood, but the worry is that alternaria is starting to infect affected plants,” said the BBRO’s Mike May.

Affected crops with yellow foliage should be checked regularly and harvested as soon as possible once alternaria has started to invade, he added.

Alternaria can cause serious rotting of roots and complete yield loss if left alone. Leaf loss also affects potential frost protection benefits later in the season.