Disease considerations at T1
Dr Jon Helliwell, Business Development Manager
At T1 in 2021, Septoria remains the main target. High disease levels are already being widely reported in the base of crops regardless of variety, and continued leaf wetness (including overnight dews) will aid transmission up to yield bearing leaves. A sub-standard level of control will allow infection to establish, increasing pressure on the T2. Disease control strategies should therefore be based around a Septoria focus at T1 and T2, with regular crop inspections undertaken to highlight any yellow rust risk. Yellow rust was readily found early in the season, but recent frosts have reduced epidemics.
Continued vigilance for yellow rust (particularly if no T0 was applied) is also required
The latest March UKCPVS meeting highlighted that across the 306 samples received in 2020 (88 different varieties), new pathotypes did emerge in 2020 but at low frequencies and with no clear geographic pattern (Click here to know more). Many RL varieties showed very good adult plant resistance, but a new yellow rust watch list is now available, capturing the varieties most likely to perform out of line with the disease ratings published in the AHDB RL. This helps to focus early-season management, particularly on varieties such as Skyfall, KWS Kinetic and KWS Kerrin. Localised changes to yellow rust populations have highlighted the need for early eradication and well-timed T1 and T2 sprays. Ensuring that the gap of fungicide protection (particularly on untreated leaf 2) isn’t unduly stretched is vital in this faster cycling disease. An additional rust-specific spray targeting leaf 2 at GS37 may be required in the highest risk scenarios if T1 applications are applied early.
Eyespot remains a key target at T1
- Only 3 varieties on the 2021-22 Recommended List have a rating greater than 5 (KWS Zyatt, Sykfall and RGT Ilustrious).
- Dose of active ingredient applied is a key consideration for effective eyespot suppression.
- Xemium® (within Revystar® XE) provides a strong level of eyespot suppression across both strains, whilst also providing additional AgCelence® benefits to straw strength, increase water use efficiency and extending the duration of green leaf area.
- Boscalid (within 0.4 l/ha Entargo®, and previously in Tracker®) remains a key active on eyespot, and can be considered at T1 in combination with Revystar® XE where eyespot risk is expected to be severe.
Later drilled cereals or those held back by recent weather will move through growth stages more quickly than usual. More backward crops will have produced far fewer leaves over winter and may visually look sparse. However crop development is largely driven by day length (modified to some extent by temperature), and so stem extension and final leaf three emergence can occur in deceptively small plants.
Careful dissection is required to determine which leaf layer has emerged in mid-April – reliance on nodes can be deceptive. Final leaf three can emerge at GS31 (rather than the normal GS32). This can have important consequences for fungicide timing to ensure adequate protection of yield influencing leaf 3, and PGR applications where label growth stage restrictions may affect applications.
If the T1 spray is applied too early, part of leaf 3 and all of leaf 2 will be exposed to disease later in the season. This has implications for the strength of fungicide required, particularly if the T2 application is subsequently delayed by weather.
In our previous blog, we are making a seasonal update: read more here.
Nitrogen use efficiency
Following the wet winter, soil mineral N levels are low and optimising capture of applied N is vital. Xemium® has been proven to improve use of applied nitrogen, enhancing green leaf retention. Appropriate manipulation of the canopy is crucial, as overly thick or overly thin crops are at increased risk of disease ingress.
AgCelence, Entargo®, Tracker®, Revystar® XE, Revysol® and Xemium® are registered trademarks of BASF. Revystar® XE contains Revysol® and Xemium®. Revysol® contains mefentrifluconazole. Xemium® contains fluxapyroxad. Entargo® contains boscalid. Tracker® contains boscalid and epoxiconazole. Always read the label and product information before use. For further product information including warning phrases and symbols, you can refer to agricentre.basf.co.uk .
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