Aphanomyces cochlioides is another fungus favoured by humid conditions that can attack beet plants after emergence. The greatest risk occurs at temperatures exceeding 15ºC and water is a prerequisite for attack by the fungus, as Aphanomyces infects the plant with the help of swimming zoospores. From a single infected plant 50,000 new zoospores can be created, which in their turn swim on and infect new plants. The infected plants become black from the root up, sometimes right up to the seed leaves, and the plants tend to fall over.

Aphanomyces can also attack big roots, which get a rot in the point or as hollows in the middle of the root. It is often not easy to see late attacks, as tops and crown are not usually affected. Increased dirt tares can sometimes show up a less severe infection at the time of delivery to the sugar factory. In some areas, the heavy rainfall received during the last few years have increased the attacks by Aphanomyces very considerably.

For many years at Hilleshög we have tested our breeding lines for resistance to Aphanomyces. Resistant varieties are available.

• Ensure good drainage. Good drainage will disadvantage the fungus, which needs damp conditions
• Take care of the soil. Everything that favours the plants at emergence, such as good soil structure without compaction damage, a high pH and preferably a little extra phosphorus, (which particularly disfavours Aphanomyces), reduces the risk of infection.
• Use fungicide treated seed. It will give a certain degree of protection during emergence and in the following weeks.
• Maintain a good crop rotation of at least four years, as the fungus survives on plant debris in the soil. If possible, it is preferable to include oats in the crop rotation.
• Avoid irrigation if the risk of infection exists.
• Choose varieties with good resistance.