Tackling Take-All With Joined-Up Management

Cambridge (August 2003) - Understanding the relative effects of different take-all control measures and the interactions between them is essential in ensuring the most cost-effective second wheat management, according to Richard Overthrow of ARC.

Richard points out that cultivation technique, sowing date, seed treatment, seed rate and nitrogen management all have an important role to play in minimising the impact of take-all; the key being to achieve the best balance between them for the specific farm circumstances.

"Cultivations can have a huge effect on take-all levels and yields," he stressed to growers at a recent second wheat management conference. "On the light soils of our Andover site, for instance, we've seen yield improvements of nearly 1.5 t/ha from minimum tillage as opposed to ploughing. This primarily results from avoiding the fluffy soils known to be associated with greater autumn take-all activity.

"These conditions apart, sowing date undoubtedly has the greatest influence on take-all development. HGCA trials across four sites over three years have shown mid-October sowings out-yielding mid-September ones by anything up to 1.5 t/ha.

"Bringing second wheat sowing forward towards the end of September is likely to make a take-all seed treatment necessary wherever the disease risk is significant," he advised. "Even with mid-October sowings, though, the need for additional measures cannot be ruled out." ARC trials clearly demonstrate the potential of take-all seed treatments to reduce whiteheads and improve yields in second wheats. They also underline the importance of correct product choice and usage for the greatest response and returns.

The organisation's most recent (2002) Hampshire site trials show major reductions in whitehead levels and significant increases in yields from the specialist seed fungicide, silthiofam (Latitude) in both September and October-sown second wheats.

At 0.9 t/ha, average yield benefits in the early sown trials were almost double the 0.43t/ha recorded from later sowings (Figure 1). And in both cases the gains from Latitude treatment were around twice those realised from fluquinconazole (Jockey).

Figure 1: Take-all control with seed treatments (ARC Hants/HGCA, 2002)

"If you want to drill early a take-all seed treatment will give you a good, economic response," observed Richard Overthrow. "Latitude has given better results than less take-all specific, Jockey in many cases, and can bring yields back to around the level of the later sowings.

"Worthwhile benefits can be obtained from treating seed for October sowings, but the economic benefits are likely to be more marginal. Seed rate is another important take-all management tool in Richard Overthrow's experience. High root concentrations in the soil encourage fungal spread to such an extent that yield reductions of over 1t/ha have been recorded with an increase in mid-September seed rates from 200 seeds/m2 to 400 seeds/m2. Yield penalties fall to around 0.4t/ha from mid-October sowings.

Interestingly, Latitude treatment has been shown to overcome this, boosting yields from the higher seed rates markedly more than those from the lower ones at both sowing dates. (…….deleted) "Nitrogen management is important too," explained Richard. "Specifically, our work at Cirencester has shown the benefit of more and larger early spring doses. Splitting a 240 kg/ha annual dressing 40% in mid-March and 60% in mid-April as against 20%:80%, for example improved yields from 6t/ha to 6.8 t/ha

"In the same trial we also found Latitude treatment effective in increasing yields by a 1t/ha under both regimes (to 7t/ha and 7.8t/ha respectively) for a 40 kg/ha N saving (Figure 2). This suggests splitting nitrogen in the right way and treating the seed could give a double bonus.

Figure 2: Nitrogen Management Strategies (ARC Cirencester/HGCA 1999)

""More recently, we've also seen definite benefits in take-all control and yields from applying Amistar (azoxystrobin) at T1," added Richard Overthrow. "This effect is not as great as can be achieved with seed treatments, but it is unique to Amistar and could be extremely valuable to crops which haven't had a take-all seed treatment. Although it's early days yet, there is evidence that the foliar spray may even be a useful addition to Latitude seed treatment in some situations."