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Rapid Disease Detection

National Snapshot project

April Week 4 2021

Leaf layer tested: Primarily leaf 4 or 5, but at some sites leaf 3

Summary: Prior to the rain arriving at the end of April, Septoria was detected on Leaf 5 at three of our sites, whilst leaf 4 remains clean of disease at all sites.

Levels are currently not concerning but the results highlight the risk Septoria tritici presents and the need to not let our eye off the ball despite prolonged cool, dry weather.

It is probably going to take several rain events to trigger a severe threat this season – so rain forecast for early May could be critical. We don’t have to look too far back to see the disease can suddenly ‘take off’. April and much of May during 2019 was dry, and Septoria tritici was barely detectable in Elation and Motown at our Callow, Herefordshire, trial site. But heavy showers in the last weeks of May saw DNA levels jump, with leaf 2 in untreated Elation recording DNA levels of 250 pg/ul.

The yellow rust situation is unchanged, although the disease has been detected on the newest leaf layer in Zyatt at one site.

Septoria tritici:

With the ‘business end’ of the season upon us, rain in late April and more possible might signal a change in disease fortunes.

We have now moved to testing the top two leaf layers to build an understanding of disease levels across the plant. Results from the last week in April reveal that the newest leaf layer is clear of disease at every site but Septoria has been detected on Leaf 5 at both our western sites and also in Perthshire, Scotland.

At J P Clay Farms in Herefordshire, leaf 5 in both September drilled RGT Wolverine (5.3) and KWS Extase (8.0) is carrying the disease. It isn’t a surprise to see it higher in Wolverine, but it isn’t alarming at 1.020 pg/ul.

Both carried Septoria tritici on emerging leaves from February, peaking in mid-March at 4.261 pg/ul and 2.69 pg/ul respectively. But as new leaves emerged in the dry, breezy conditions of April so the disease fell away. CTM Gareth Bubb thinks the upturn is down to the recent run of cool nights and mornings dews.

Septoria tritici is also present in leaf 4 of Zyatt (6.4) as is yellow rust (5) at Water Lane Farm, Lancashire. A Septoria tritici reading of 0.885 pg/ul isn’t troubling Spunhill agronomist Paul Cawood. At the same site early September drilled Extase is also holding some disease on leaf 4. But again, light at 0.12 pg/ul.

Cold dry weather has delayed T1s across the country but crops will soon catch up and it is likely that the gap between T1 and T2 will be shorter than normal.

Yellow rust:

Yellow rust remains undetected on the two newest leaf layers at all of our National Snapshot farms.

April week 4 results

Septoria results for April week 4

 

To download as a PDF click here.

April Week 2 2021

Leaf layer tested: Newest leaf layer, identified as final leaf 4 at some sites.

Summary: Cool, dry weather has limited the spread of disease from lower leaves onto Leaf 4 reassuring growers that T1 fungicide applications will be protectant. Growth stages vary from GS22 and GS32 and care needs to be taken to correctly identify Leaf 3 for accurate T1 timing.

Septoria tritici:

With the latest round of testing revealing new leaves free of Septoria tritici at all of our sites, T1 sprays are likely to be protectants only, giving growers options on products and rates.

Edward Vipond at Troston Farm, Suffolk, and James Nott of Ovington Hall on the Suffolk/Essex border, are two examples.

At Troston Farms, Septoria tritici was picked up in Skyscraper (5.1) early on in the year, and was found to be present on newly emerged leaves up until the third week of March. . Firefly (6.8) too returned a positive result in the latter stages of March. Septoria tritici also appeared in Insitor (6.8) at Ovington Hall at the same time, and was again there during the first week of April.

With leaf 4 now emerged on Skyscraper, Firefly and Insitor, all are clean indicating that disease has not transferred from the lower leaves where it was detected in the preceding weeks

Edward has earmarked Ascra for T1 sprays on the farm but is still to decide on fungicide make up and rates for the two National Snapshot plots. He is surprised at the levels of Septoria tritici in the base of both Skyscraper (5.1) and Firefly (6.8) but the cool conditions mean leaf 3 is still a little wayfrom 75% emerged.

He ponders whether dry April weather is now the norm. Typically, they can expect around 55mm of rain for the month, but so far precipitation has been nowhere near that. With high pressure forecast to run into May, any change is unlikely.

The impact of dry conditions on crops and disease across the country is noticeable. Southern sites are showing signs of crop stress and that could spread. In Scotland Grant Reid has never seen the ground so dry for mid-April. September drilled susceptible Skyscraper (5.1) and Elation (4.1) at Perthshire and Lothian respectively recorded no infection on the newest leaf.

It is the same picture at Irish sites Balyraggert, Co. Kilkenny and Dunshaughlin Co. Meath.

Earlier in the season at Co. Meath, Mick Marmion and Bayer CTM James Byrne recorded low levels of Septoria tritici as new leaves emerged in September drilled Graham, rated at 6.0 in Ireland. This peaked at 3.251 pg DNA in the third week of March but with Graham now near GS30, new leaves are free from infection.

Yellow rust:

There is no change in the yellow rust situation which is again undetected in new leaves across all sites. Although cool and dry a possible explanation is that the breezy conditions are reducing canopy humidity and restricting the disease from spreading to new leaves.

April week 2 results

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To download as a PDF click here.

April Week 1 2021

Leaf layer tested: Newest leaf layer, identified as final leaf 4 at some sites.

Summary: As cool and breezy conditions continue this April, coupled with some sharp overnight frosts, the impact on disease levels is being seen across the country. Septoria and yellow rust pressure remains low across all sites that are being tested.

Septoria tritici:

With many crops at or near GS30, Septoria tritici is only being detected on the newest leaf layer at a few or our sites, which are all September drilled fields. It does include Insitor (6.8) at Ovington on the Suffolk/Essex border but at just 0.566 pg DNA it is low and similar to levels seen in mid-March. Some leaf infection is visible but again, minimal.

Septoria tritici is present on the newest leaf layer at both Middlebank Farm and Keillor Farm, Perthshire, but not at levels detected earlier in the season.

Skyscraper (5.1) is considerably further ahead than Sundance (7.9), which is only at GS22. Grant Reid is a little puzzled by this as there’s little difference in soil fertility or farm nutrition strategies. He thinks it is likely that as the weather warms Sundance will catch up, but that remains to be seen.

A possible issue ahead of T1 sprays is leaf 3 identification. At D J Tebbit Farms Ltd, Cambridge, Ben Giles needed the aid of optics when dissecting plants with farm manager Russell McKenzie. They expect the T1 timing to be about 5-7 days later than usual and Ben cautions care is needed when dissecting plants. With flag leaf and leaf 2 just a few millimetres long at the moment, they found it difficult to establish which leaf they were looking at. The concern is that what might look like leaf 3 could be leaf 4 with leaf 3 still to unfold.

Septoria tritici is normally the target disease for Mark Wood of J P Clay Farms, Herefordshire, but whilst the disease was detected on the lower leaves of his September drilled Wolverine (5.3) earlier in the season, there is currently no disease present on the newest leaf layer. With T0 sprays cancelled he is thinking about T1 plans. If it stays dry, he will consider azole + multisite. If an eyespot threat develops, he will probably opt for Firefly (prothioconazole + fluoxastrobin) with multisite.

Yellow rust:

Although yellow rust has been observed in some more susceptible varieties, the disease has not been detected on the newest leaf layer at any of the National Snapshot farms. Leaf 4 is clean in both Graham (8.0) and Skyscraper (8.0) at Long Sutton, despite both being drilled late and the farm just over a mile from The Wash.

April week 1 results

Return back to Rapid Disease Detection National Snapshot Project home page for more results.

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 To download as a PDF click here.

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