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This category contains a series of diseases caused by fungi that attack the beet leaves:

  • cercospora leaf spot
  • powdery mildew
  • rust
  • ramularia leaf spot

Their symptoms generally can be observed during the summer (in the beginning of the summer for cercospora leaf spot and powdery mildew; somewhat later for ramularia leaf spot and rust) until harvest.

Cercospora leaf spot

Cercospora leaf spot (Cercospora beticola) is characterized by the appearance of grey spots on the leaves with a red or brown margin and with lots of tiny black eruptions. In case of severe attacks, these eruptions may expand and result in the complete desiccation of the leaves. The plant then reacts by producing a fresh growth of leaves.

In Europe cercospora leaf spot is the most harmful leaf disease. It develops rapidly and requires vigilance as to the phytosanitary treatments. It is the only disease for which a treatment at least one month and a half before harvest still can be cost effective.

As the fungus thrives under warm and wet conditions, the attacks of the cercospora leaf spot will be more frequent and more damaging in hot and thunderous summers, i.e. in South Europe, central Europe and the Balkans. However, in recent years, it has gained in importance in other European regions. However, it is not present everywhere in Europe.

Rust and powdery mildew

Rust (Uromyces betae) and powdery mildew (Erysiphe betae) can be easily identified. The first is characterized by red-orange pustules; the second by a whitish duvet on the upper part of the leaves. These two diseases are very frequent. While powdery mildew may cause important losses in case of strong pressure, whilst general terms causes less harm.

Ramularia leaf spot

Ramularia leaf spot (Ramularia betae) has symptoms resembling to those of cercospora leaf spot: whitish spots develop with a brown edge (red to brown spots for cercospora leaf spot) and full of little white points (black points for cercospora leaf spot). This disease above all causes losses in sugar content and is widespread all over Europe. Today however it is less common in our regions than some years ago. The fungus responsible for the disease prefers relatively fresh and rainy summer weather.

Control

The protection of the beet against leaf diseases is expressed around two main centers of interest:

1. Agronomic measures

  • Avoid a too short crop rotation
  • Good management of the crop residue in storage areas, that act as ‘reservoir’ for these fungi
  • Possibly choose a variety that is less sensible to leaf diseases (especially in the beet areas of Europe where damage due to cercospora leaf spot is frequent and important)

2. Crop protection

In certain regions, there is an industry network for the observation of symptoms of leaf diseases. When a disease is reported in one region or another, it is important to check your own fields to see if the disease is also observed there. If this is the case, before any spraying with an adequate fungicide, the beet grower will count and make sure that the intervention threshold is exceeded. According to the regions, 1 to 3 treatments will be needed. It is important to alternate the type of active ingredient used and not to spray too late in the season.

Data sheet

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