Use Sclerotinia sprays to top up OSR light leaf spot (LLS) control this spring. Thats the advice of ADAS expert Peter Gladders who says that some crops are already heavily infected despite two azole treatments.
Dr Gladders is warning of severe pressure following weather conditions that have favoured the disease coupled with the inability of growers to get on. Pigeons have stripped the leaves off many crops and it has been necessary to delay sprays until there is leaf to target. With infection on embryonic leaves and flower buds weve got to expect severe infections now, whatever is done, he warns.
He points out that eradicating the disease isnt possible but that growers will need to supress further infection. The severity of the disease is almost too much to keep on top of. Even for those that have managed to apply a spring treatment the pressure is so great that its likely that sprays will run out of steam. My advice is to protect side branches and pods, especially as rapeseed prices remain buoyant.
And with flowering likely to be late and fast, he argues that this will give growers another bite at the cherry. Last season we witnessed the dilemma growers faced as extended flowering and poor weather complicated sclerotinia control strategies, but that is unlikely to be the case this spring. Growers can expect to see effective control from a mid-flowering spray which means that anything pre or early flowering can then be used to target LLS too, he notes.
He also reminds growers to take care with product choice. The last thing backward crops will need is any growth regulation. Make sure you choose a product without a PGR effect, he cautions.
Bayers Phillippa Overson agrees and reminds growers that prothioconazole remains the most active LLS treatment. Theres still nothing that really gets close to prothioconazole when it comes to LLS, and it remains one of the best choices for sclerotinia too. Proline275 (prothioconazole) this season has the advantage of excellent disease control without any PGR effect so is a very good choice.
As prothioconazole is highly persistant against sclerotinia we always advise growers to use this as the first treatment in a two-spray flowering programme, this is more pertinent than ever given the increased LLS threat this season, she concludes.