Alternaria is not a very aggressive disease, but the fungus attacks when the plant is weakened or stressed for other reasons. For example, Virus yellows, which is transferred by aphids, might be the primary attack. In other cases hail or insects might have damaged the leaves, giving a foothold for Alternaria. Magnesium, manganese or boron deficiencies are very often the main cause of an attack. Alternaria can be present under a wide range of climatic conditions, but damp and rain favours the fungus. Attacks normally appear late in the season and seldom cause major yield loss.

• Choose a good insecticide on the seed to keep aphids away from the young plants during the first months, which will reduce the risk of Virus yellows
• Be observant and keep a close check on aphid attacks.
• Be careful of plant nutrition and avoid deficiencies in the beet crop.