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Cercospora Leaf Spot (CLS), caused by the fungus Cercospora beticola, can cause significant yield losses (up to 50%) in sugar beet crops around the globe. In the UK it has been a sporadic problem, due to the nature of the disease, which requires favourable environmental conditions (warm and wet for a prolonged period) to thrive and cause significant levels of defoliation.

The EU ban on neonicotinoids in 2018 fundamentally impacted the industry, with the subsequent use of Thiamethoxam treated seed only available under a Defra derogation when the ‘Rothamsted’ VY model predicted incidence above a set threshold.

This work is extremely timely as the UK 2020 aphid/virus situation has been unprecedented, following the exceptionally mild January and February (reflected in the Virus Yellows forecast issued by BBRO to Industry in early March) and exacerbated by the warm, dry spring encouraging an early migration of large numbers of aphids, particularly Myzus persicae, to build up in spring crops such as sugar beet.

The most important fungal foliar diseases affecting sugar beet in the UK have historically been rust (Uromyces betae) and powdery mildew (Erysiphe betae), both of which have been well controlled by a combination of azoles and strobilurin fungicides. 

Plant parasitic nematodes (PPNs) are important pests for many crops globally and result in a c. 14% loss of production annually, which equates £132 billion. The sugar beet crop is no exception, being subject to infection by a variety of different PPN species, including those categorised as free-living.

The use of fungicides in sugar beet has become commonplace in the past 10-15 years with the majority of crops now receiving two sprays per year, and late harvested crops up to three. 

Infection by beet yellowing viruses causes a significant risk to sugar beet yields. Beet yellowing viruses comprise Beet Yellows Virus (BYV), Beet Mild Yellowing Virus (BMYV) and Beet Chlorosis Virus (BChV), all transmitted by the aphid Myzus persicae via primary and secondary infection modes. 

This project will provide information to determine whether any current/future RL varieties respond differently to virus yellows infection (BMYV and BYV) and hence lose less relative yield, if such varieties cannot be protected by neonicotinoid seed treatments in the future. These additional data will also help to improve the virus yellows-variety element of the current BeetGro yield model as currently these are based on average yield responses and are not variety specific.