Thelatestresults from fungicide performance trials against phoma leaf spot show thatgood control can be achieved with a two-spray programme, reports the HGCA.
Treatmenttiming is important to get the best control, the first application should bemade when 1020% of plants have phoma leaf spot and the second application whenreinfection is evident 4 to 10 weeks later. In trials, half rates weresufficient to get good control and a significant yield benefit.
Thephomaforecast can help with spray decisions by providing an overview of phomalevels at a number of trial sites across the UK. However, the dry weather inSeptember has led to patchy development with no consistent regional pattern, sowalking and monitoring crops is essential.
Weare seeing the first symptoms of phoma leaf spot in crops now and, with recentrain, are likely to see threshold levels in some crops in the next few weeks,says Dr Faye Ritchie of ADAS. All triazoles are good as protectants so, formany growers, product choice will depend on other features.
Curativeactivity, for example, with prothioconazole products, is important when smallplants are infected. Products with plant growth regulatory activity, such asmetconazole or tebuconazole may be favoured as protectants where plants arelarge and reach six leaves by mid-October.
Thisautumn, an SDHI + strobilurin co-formulation, known as Refinzar, isavailable for the first time, full details about how it performed, as well asan update on currently available products, is available in the fullreport.