Managing early-drilled second wheats to minimise the impact of take-all
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About this project
In a 3-year HGCA-funded study between 1998 and 2000, it was shown that, even when seed treatments such as silthiofam and fuberidazole + triadimenol are used that can reduce the impact of take-all, it is still important to delay the sowing of second wheats from September until October, and to employ other crop husbandry measures that can help to alleviate the effects of the disease. Both seed treatment and sowing date can have implications for selecting an appropriate seed rate, and the project therefore investigated the effects of seed treatment on response to seed rate between 200 and 400 seeds/m2, using fludioxonil as the control.
In the 2001 season, the seed rate range was extended down to 100 seeds/m2, and a fourth seed treatment, fluquinconazole + prochloraz, was added. Three replicated trials were conducted at contrasting locations, with a target sowing date of late September. Plots were assessed for crop structure and yield components, take-all incidence and severity, and grain yield. Results were compared with those obtained in the 1998-2000 seasons.
Take-all was present at all three sites, but seed treatment differences were only recorded at two. Take-all severity in April was lower for fludioxonil + silthiofam and fluquinconazole + prochloraz than for fludioxonil alone. At one location, a higher incidence and severity of take-all were recorded at seed rates of 300 or 400 seeds/m2 than at 100 or 200 seeds/m2 with treatments that did not give control of the disease. Yield differences between seed treatments varied between sites, but fludioxonil + silthiofam was the highest ranking overall. A seed rate of 100 seeds/m2 was below optimum regardless of treatment, but there was evidence of an interaction between seed treatment and rate at one location. The other treatments had a greater yield advantage over fludioxonil alone at the two higher seed rates than at the lower rates. However, the optimum seed rates (200-300 seeds/m2) were the same for all seed treatments except fuberidazole + triadimenol (200 seeds/m2).
Comparison of the 2001 results with equivalent trials in 1998-2000 showed similar seed rate responses for both fludioxonil alone and fludioxonil + silthiofam, although the yield benefit from silthiofam was above the previous average. The response for fuberidazole + triadimenol was different to previously. Increases in take-all incidence at higher seed rates had also been observed in some trials during the other three years.
The results suggest that, like silthiofam, a seed treatment based on fluquinconazole can give partial control of take-all. However, seed rate is also an important factor in managing second wheats at risk from take-all. Use of a non take-all seed treatment at a higher seed rate may cost less than a take-all treatment at a lower seed rate, but this could further depress yield. As later drilling is a key measure to reduce take-all impact, seed rates should however be adjusted to take into account sowing date, soil type and seedbed conditions.
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