Despite the prolonged cold spell, wheat is rapidly approaching GS 32 in the eastern counties and with it, Septoria pycnidia can be easily found, warns BASF. High levels of Septoria are typical across the UK and are cause for concern. The weather pattern has been very conducive for Septoria – plenty of rain splash events and generally warmer temperatures. This will mean that apparently clean crops will already be infected, but the symptoms will not show for 3 weeks or so after leaf emergence. With further rain forecast and leaf 3 emerging at the same time, it is a potential recipe for disaster as these rain showers will facilitate movement of Septoria up the plant to the upper leaves that are responsible for yield. It is absolutely crucial that a robust fungicide at a robust rate is applied at T1 to fight established infection and protect Leaf 3 to manage later infection up the plant. It only takes a small amount of inoculum to result in an epidemic and there is plenty of Septoria in crops now.

Rust which had slowed with the recent cold, has now re-appeared in many crops, not just the usual varieties. In fact, it never went away; older leaves died off with the frost but it has been lurking in the base of the plant and inside new leaves. Reports of high rust levels are now coming in from all parts of the UK.

Steve Dennis, BASF’s field sales manager, has contact with advisors around the UK. “I’ve had several calls this week from agronomists wishing to discuss their rust control strategy. The cold conditions in March seemed to stem the disease’s development and there have been a number of recent articles suggesting the disease is now absent, but over recent days it has come back with a vengeance and not just in the expected varieties. I would advise keeping a very careful watch on all fields as the situation is in flux, make sure whatever you choose at T1 is strong against Septoria and rust as they are both on the move and if in any doubt, the safe option would be Adexar + CTL.”

It is tempting to trim back costs by using a non-SDHI option at T1, but where Septoria is established, a triazole + CTL T1 spray will not be able to deliver the eradicant/curative activity needed to control infection that is already there. Where growers are looking to trim costs, cutting back at T1 will be a false economy and won’t pay in the long run, as you are compromising yield and will cut overall profits. Where T0 applications have been applied late or not at all, an SDHI at a robust rate is strongly advised.

Under this season’s circumstances, Adexar (Xemium and epoxiconazole) makes good economic sense at this timing, the quick action and continuous delivery of Xemium over time will ensure sprayed leaves will be well protected. If Septoria has reached the stage at which symptoms have become visible, only Xemium will have an effect on further disease development. Xemium products – Adexar and Librax (Xemium and metconazole) deliver THE BEST eradicant and curative activity available.

This view is well supported by the results of a survey of independent agronomists taken this month, where 77% ranked Xemium the number one SDHI against Septoria, well ahead of the other new generation SDHI’s. The next nearest candidate in the survey was penthiopyrad with 17% ranking it as the best against Septoria. So, five times as many agronomists chose Xemium over the next ranked SDHI on Septoria, which is the Number 1 disease in wheat. 

With a range of growth stages, active Septoria and frequent rain showers – a triple whammy in epidemiology terms – wheat crops will need to be checked regularly and whilst every effort is made to apply fungicides on time, it is realistic to expect some delays due to bad weather, mis-diagnosis of growth stage or simply workload where not everything can be sprayed on time. In the likely event that this will occur Adexar with curativity and long lasting protection is key. This season growers need a robust T1 fungicide that can carry through to T2 Otherwise both leaf 2 and leaf 3 could become infected and you are back in a curative situation at the T2 application time, again compromising yield. If you skimp at T1 you may be forced to spend extra firefighting and rushing around applying a T1.5 spray costing more money than if you’d spent more wisely at T1. 

Summary

• Watch out for active Septoria now – beware of risk to emerging leaf 3 as rain forecast.
• Crops are now approaching T1 timing – spray when leaf 3 is fully emerged on the main stem.
• Why use an SDHI at T1 this year? – established Septoria, high disease pressure and long lasting protection.
• A robust SDHI at a robust rate is essential to protect leaf 3.
• Adexar is the best option – it gives the best eradicant/curative activity, broad spectrum disease control, long lasting protection up to T2, competitive on price.
• Make sure your chosen T1 is strong against rust, it is moving now.

BASF notes that now wheat is worth less than £100/t, growers may look to cut costs. But they say raiding the fungicide budget could backfire. Profit is linked directly to yield and fungicides are directly linked to yield production, keeping disease out and leaves greener for longer equals more yield. Trials by BASF and independent institutes show consistently across the major wheat growing areas, a yield benefit of Xemium over bixafen of >0.2 t/ha at commercial dose rates. At today’s wheat prices this results in more than £20/ha additional profit from using Adexar and Librax instead of Aviator. (Source: ADAS, SRUC and NIAB TAG – over 70 comparisons in 2014 and 2015).

You can be confident that whatever the season brings, whatever the disease pressure, it pays to invest in disease protection. Every year a robust fungicide programme increases yields and margins, and those that include Xemium give an even higher return than other SDHI’s.