Oilseed rape crops couldbe at greater risk from a three-way disease attack this season so growers mustadopt a robust fungicide strategy from the outset, leading agronomy firmHutchinsons warns.
Warmand damp conditions during August have been conducive to development andcarryover of key soil-borne diseases and any early-sown crops could be atparticular risk from phoma, light leaf spot and verticillium wilt infection,says the firms technical manager Dick Neale.
Althoughharvest is late, a lot of rape has already been drilled where previous cropshad failed and it is growing very quickly in the warm, moist soils. The lateharvest and a continuing trend for shallow cultivations also mean there is alot of crop residue on or near the surface carrying phoma spores that needwarmth and moisture to sporulate.
Itis therefore much more likely that the 10% infection threshold for the firstfungicide spray will be reached earlier than normal, possibly by the first weekin October if conditions remain conducive to disease development, says MrNeale.
Heurges growers to monitor crops closely and use the Rothamsted phoma forecastingtool in order to help time sprays accurately. A robust dose (0.75litres/ha) ofprothioconazole/tebuconazole can be more effective than straight metconazole,he suggests.