With winter crops generally faring well in the West, but spring crops struggling as a result of delayed sowing, farmers in the region took the opportunity to visit ADAS Rosemaund’s open day.
The need for two SDHI fungicide applications to wheat varieties with high levels of resistance to septoria is ‘very debatable’, argues ADAS’s Dr Jonathan Blake.
Presenting results from the first two years of a three-year trial over six UK sites, aiming to determine the value of agronomic factors in controlling septoria, he said resistant varieties sown late (mid-October) had consistently less septoria.
The varieties trialled in 2016 and 2017 were KWS Santiago (susceptible), JB Diego (moderately susceptible) and Revelation (resistant). “With Revelation there was no benefit of adding an SDHI at all. Using two SDHIs on Revelation sown in mid-October was a waste of time and negative in terms of cost. A lot of people are using two SDHIs at T1 and T2.”
For farmers looking for a ‘belt and braces’ approach with resistant varieties such as Revelation and Graham, he suggested applying just one SDHI at T2.
Optimisation of seed rate and drilling date using a shoot production model could provide an alternative to chemical methods of controlling wheat bulb fly (WBF), according to ADAS entomologist Dr Steve Ellis.
“Wheat produces more shoots than it needs to achieve potential yield. The minimum shoot number for the average UK yield is about 400 shoots/sq.m. Excess shoots can be sacrificed to pests without affecting yield,” he says.
Wheat bulb fly risk can be assessed as low, medium or high, depending on numbers of eggs/hectare and once the model is fully developed, the aim is to be able to use this information to optimise seed rate and sowing date for different WBF pressures, says Dr Ellis.
For each week wheat drilling is delayed after late September, target plant populations should be increased by 10 plants/sq.m, according to Dr Christina Clarke of ADAS.
“Establishment is often estimated at 85 per cent, however, an AHDB-funded review of more than 1,000 records found average establishment was only 67 per cent with a large amount of variation. Time to emergence increases with later sowing dates due to lower temperatures. Establishment is also reduced by 2.6 per cent for each 100 seeds /sq.m increase in seed rate.”