Recent drier weather and the predicted arrival of winter conditions this autumn might come to the aid of growers looking to reduce OSR inputs.
Certainly thats the hope of one grower, RussellMcKenzie of John Sheard Farms, Cambridge. He is planning a 1.7 L/ha dose ofKerb (propyzamide) with 0.46 L/ha of Proline275 (prothioconazole).
He is in this position through favourable weather and the switch to hybrid varieties. We are now predominately hybrids. Their autumn and spring vigour gets them moving but most have good phoma resistance too. That resistance delays the onset of the disease so we can come in with a multi-faceted approach in late November or early December.
However, we always keep a close eye on crops fromOctober onwards, especially the more susceptible ones. If phoma is present early in the season we will see the crop through to November with an application of something likePlover (difenoconazole), he notes.
Those hybrids have plenty of potential. Most fields have established well and the only disappointment is some late drilled crops ravaged by cabbage stem flea beetle.
But despite the promising outlook he warns that there could be a sting in the tail. Its no good if the benefit of taking outa pass is lost through poor control. Kerb sprays must be applied when ground conditions allow and disease control will need to be built around potentactives. Not only will crops need protecting against light leaf spot (LLS) butan active with phoma potencywill be needed too.
Indeed so important is LLS control now that MrMcKenzie rates it as critical as canopy manipulation. Research has demonstrated the importance of light penetration of the canopy to set and fill seeds, but research, and in some cases personal experience, has shown us the necessity of LLS control too. If it gets in then it can cause great damage -you must try and stay in a preventative position.
For that reason Mr McKenzie will get back in at the first opportunity post winter. Often the decision to treat is an easy one, but what with less so. Tebuconazoles PGR activity can be useful, but it is weaker on LLS than prothioconazole. You have to weigh-up the risk and achieve the right balance between LLS control and PGR, he suggests.
Tim Nicholson of Bayer agrees and reinforces the point to control both diseases. Theres only a few varieties with good resistance to both diseases. LLS is hard to identify and phomas latent phase can be as little as 10 days. Growers can be caught out by both diseases which is why prothioconazole is so important as part of autumn strategies, he notes.
And he warns against complacency with the publication of the latest LLS forecast. The threat is lower than last year but still high for all areas. However, compare that to the LLS forecasts issued a few years back and you will see how the situation has changed. I would advise growers to follow Mr McKenzies approach and be on the lookout for the first signs of LLS from mid-January onwards, he concludes.