Risk of disease still high in lettuce in UK

ADAS experts are warning lettuce growers that the risk of disease is still high, despite the very cold winter and the dry spring.

The experts are warning that downy mildew and Botrytis pose a threat in lettuce, when unsettled weather returns. They also say that the cold winter weather will not have reduced the risk of Sclerotinia, as most lettuce have been planted on fields where Sclerotinia–susceptible crops have been grown in recent years. "Sclerotia germination in arable crops has also been reported in the South, West and North, regions where salad crops are grown," adds Simon Townsend, Speciality Agronomy Manager for BASF.

He points out that lettuce needs to be protected from a range of diseases that affect both yield and quality. "The use of a comprehensive fungicide programme will help in the production of high quality salad crops with good visual appeal, which means good sales and returns for growers."

This year growers of outdoor and indoor lettuce have the option of integrating the protectant and systemic fungicide Signum into their disease programme. "Signum had its label recommendation for use in lettuce re-instated this year. The combination of boscalid and pyraclostrobin in Signum offers broad-spectrum disease activity and high levels of performance. In trials and in commercial use it has regularly produced excellent control levels of Sclerotinia, Rhizoctonia and Botrytis. Signum is also active on non-label diseases such as Stemphyllium and has additional positive effects on reducing the incidence of post-harvest symptoms such as Pink Rib, discoloration and dehydration," reports Simon.

Simon reports that in trials Signum reduced Sclerotinia from 69% in the untreated to just 23%, resulting in yield increases of 75% over the untreated. "Its use also reduced Botrytis levels from 40% to 4%, increasing yields by 78%. In further trials aimed at Rhizoctonia, Signum increased the percentage of marketable heads by 146%."

"Many salad growers appreciate the excellent disease control as well as the additional effects that Signum has on quality, yield and shelf-life characteristics. In a market where quality and visual appeal is key, broad-spectrum disease control plus additional quality criteria are important to growers."

For Sclerotinia control, Signum should be applied as a protectant fungicide at a dose rate of 1.5 kg/ha in water volumes of 200 to 900 litres before infection has taken place. As infection in lettuce takes place on petioles and older leaves in contact with the soil, it is better to make the first application of Signum before the outer leaves touch the soil and as early as possible in the spray programme. Two applications can be made to the crop.

Signum also has SOLAs for many other crops including protected leaf herbs and protected and outdoor leafy brassica crops grown for baby leaf production. Growers intending to use a SOLA require a copy of the SOLA notification document, which they should keep with their records. Individual SOLA notification documents can be viewed and downloaded from the CRD web site.

Source: Farming UK