Management of the beet cyst nematode on sugar beet and brassicas

Beet cyst nematode is an important pest of sugar beet and affects related crops such as spinach, mangold, fodder and red beet. Tolerant varieties are available, but the most effective form of control is rotation to reduce populations in the soil. Brassica crops such as oilseed rape, cabbage and Brussels sprouts are effective hosts for this pest.

• Cysts are spread in soil, attached to beet roots, farm machinery and footwear, or by floodwater
• Most common in sandy or peaty soils
• Oilseed rape and other brassica seed crops are particularly efficient hosts and can lead to a quick build-up of the pest
• BCN is most likely to be found on sites with close rotations of beet and/or brassica crops and where host weed species, such as charlock and fat hen, are not controlled

Scientific name: Heterodera schachtii

Cysts are lemon-shaped (0.5 x 1 mm) and, initially, white, turning brown as they mature. They are present on the roots of beet from the seedling stage until harvest. They can easily be confused with grains of sand. It is easier to see them on gently washed roots using magnification.

Juveniles have slender, transparent bodies measuring 0.5 mm in length and are too small to be seen without magnification.

Cysts in the soil can hatch with or without the presence of hosts, but root stimulants, produced by host plants, encourage additional hatching and attract the larvae to the roots.

The juveniles move through the roots. After mating, males return to the soil, while females remain within the root and begin to swell, forming cysts that can fall off into the soil to repeat the cycle. Cysts can remain viable in the soil for many years, containing up to 600 eggs.

The life cycle completes in 300 degree-days above a base temperature of 10°C. In northern Europe, it can complete two or three generations per year, depending on weather conditions.

Crop damage is usually evident as patches of stunted beet, which wilt easily in dry periods. Affected plants produce many lateral roots, in response to the root damage: an effect known as ‘bearding’.

In sugar beet, yield reductions of 30–60% occur, depending on the level of infestation.

Non-chemical control

Widen the rotation to reduce cyst numbers. Do not use oilseed rape and other brassica seed crops as break crops in cereal rotations that also include sugar beet.

Nematode-resistant brassica catch crops, such as white mustard and oil radish, can prevent an increase in inoculum for the following beet crop. Sown in the autumn, they encourage eggs to hatch but are resistant to colonisation by the juveniles.

Nematode-tolerant sugar beet varieties are on the BBRO Recommended List.

Monitoring

Sample soils and use commercial services to determine egg/larval concentration in the soil.

Thresholds

Thresholds vary widely across Europe. In the UK, there is an economic benefit associated with BCN-tolerant varieties above two eggs and larvae per gram of soil.

Insecticide resistance

None known.