South East: Agronomy pointers for May

Crop Progress

In comparison with other parts of the country, crops in the south east look decent. Obviously, there are some areas that have been impacted by more water damage including some fields drilled around the time of autumn storms where crops have tillered less.

But generally, crops in Hampshire over chalks are looking well, and further east into Kent, there are some very good looking crops as we reach the last 10 days in April. On the heavier, stickier soils on the Weald in Kent, crops have struggled a bit more and the soil has taken a long time to dry out.

Jobs have backed up on farm, but some better weather in the middle of April saw fertiliser spreaders and sprayers start to catch up.

Leaf three in wheats emerged more quickly than perhaps expected especially in coastal areas making T1 timing tricky. Most T1 will have been applied before the start of May, with the majority sprayed from around 20 April – time will tell whether leaf three was exposed for too long in some crops.

Oilseed rape also came into flower early and there will likely be a prolonged flowering period.

Richard’s agronomy tips for May

Aggressive Septoria could require robust control

Most wheat in the south east was drilled before the worst of the autumn storms, which most growers will no doubt be thankful for. But earlier drilling and the impact of weather is meaning there is some aggressive Septoria bubbling away on leaves five and six at the bottom of canopies in most varieties, almost regardless of AHDB resistance ratings. As this is written it is looking like a high disease pressure year for Septoria, which really got going in the brief warmer spell that coincided with some showers.

The other disease to look out for this year is brown rust, especially in susceptible varieties such as Crusoe, Extase and Mayflower. It’s unusual to be seeing such high pressure so early on in the season, and we know from past experience that once it is in the plant it is a very difficult pathogen to eradicate which has been seen by the lack of control from T0 applications of tebuconazole.

Vimoy® has excellent brown rust activity however if there’s high levels of active rust present at T2 then the addition of a robust rate of either strobilurin or tebuconazole would be recommended.

Finding active brown rust at such an early part of the season could be due to the mild winter we’ve just had, however it’s always best to monitor abnormal disease occurrence, and the best way is to send samples into UKCPVS to check for any changes in race.

Below are some links with further information on UKCPVS.

https://ahdb.org.uk/knowledge-library/uk-cereal-pathogen-virulence-survey-ukcpvs

https://www.niab.com/research/agricultural-crop-research/research-projects-agriculture/uk-cereal-pathogen-virulence

Unfortunately, this combination of disease risk and current weather is not the farmer’s friend this season, and will likely need to be met with some robust fungicide protection at T2, unless the weather changes dramatically through May.

Fungicide options at T2 will depend to some extent on what was applied at T1. For example, if you used our new Iblon-containing fungicide Vimoy® (isoflucypram) + Proline® (prothioconazole) at T1, it won’t be an option at T2 because you can only use one application in a season.

In that case, something like Univoq® (fenpicoxamid + prothioconazole) is a very good alternative active against Septoria. Where brown rust is a potential threat, then it would be worth adding tebuconazole as Univoq’s® Achilles heel is brown rust.

If Vimoy wasn’t used at T1, this could be a perfect choice for T2 offering excellent control of Septoria and both yellow and brown rust. Where Septoria pressure continues to build through May, then it’s possible to use Vimoy® in conjunction with Jessico® One (fenpicoxamid) for the strongest possible combination rather than with Proline® .

In trials Vimoy® / Jessico® One last season gave excellent results – just remember it is the same active as in Univoq® and therefore comes with the same caveats around use, especially with regards to water volumes and washing out post applications. You can find the detailed advice on our website.

There’s also the registration of SDHI adepidyn® from Syngenta, which could be an option at T2, although obviously I have less direct experience of its potential.

In the event the weather is kinder and disease pressure is lower than it currently appears, or if crop potential doesn’t justify more expensive inputs, there are other alternatives at T2. Ascra® (bixafen + fluopyram + prothioconazole) gives excellent all-round disease control, for example, while also delivering high grammes of SDHI-containing actives which brings good physiological benefits.

Another possibility would be mefentrifluconazole, while Elatus® Era (benzovindiflupyr + prothioconazole) could be used to fend off rust diseases, albeit at the expense of better Septoria control.

Brown rust and Ramularia head winter barley disease concerns

Winter barley crops are all over the show, with the crop not having fared well with all the rain we’ve had. On free-draining soils it is now moving forward in a good way, but on heavier colder soils it has been held back and suffered as a result.

The wet weather has encouraged a lot of the wet weather diseases in winter barley, while brown rust has been a problem especially in hybrid barley varieties. That will need looking out for at T2, along with Ramularia.

Ramularia hasn’t been much of a problem in the south in the past couple of years, possibly because it tends to be a later season disease and winter barley in the south tends to senesce that little bit earlier.

However, it tends to infect stressed crops, which this year’s circumstances are causing to some extent.

That might lead to Ascra® at 0.9 L/ha being a good choice for T2 awns emerging sprays in winter barley, if it wasn’t used at T1. Another choice for Ramularia could be Revystar® (mefentrifluconazole + fluxapyroxad), although in malting barley watch out for the GS45 cut off for the latest time of application. That’s before awns are visible (GS49), which is a source for infection, while Ascra® can be used until GS61 (start of flowering).

Where Ascra was used at T1, Siltra® (bixafen + prothioconazole) remains an excellent all-round choice, especially for the wet weather disease, Rhynchosporium, where it is one of the strongest options.

One spray strategy for spring barley

With the cold, wet soils leading to slow emergence and a later-than-usual drilling period for spring barley, the likelihood is that a one-pass fungicide programme should be sufficient in most crops this year with it racing through growth stages once it picks up some nutrition.

If that’s the plan, then Ascra® at 0.7-0.9 L/ha around GS31/32 would be my choice. Maintaining as many tillers as possible will be important and the use of SDHIs in Ascra® will give the best chance of retaining and promoting growth.

Prolonged flowering in OSR might require second spray

Oilseed rape crops began flowering early this year, but with secondary growth pushing through the canopy, it’s looking like a very prolonged period of flowering.

That probably means a second spray to protect against Sclerotinia may be required, particularly if rain is still forecast. In some cases that spray might have already happened but with workloads in late April I can see that being pushed into early May for some growers.

Aviator® (bixafen + prothioconazole) is a proven strong option for Sclerotinia control and against light leaf spot, with trials showing a 0.3t/ha average yield improvement over farm standard treatments. For a second spray a rate of 0.5-0.75 L/ha could be used.

An alternative could be Proline® (prothioconazole) plus azoxystrobin, especially if Aviator® was used as the first spray.

Watch for quick emerging potatoes

Potato planting was delayed by the wet weather, but planting pace picked up from the middle of April.

With seed potatoes likely to have broken dormancy and being planted into warming soils, emergence is likely to be faster than usual. That might mean applying pre-emergence herbicide applications including Emerger® (aclonifen) in a timely fashion as they need to be sprayed at least seven days before crop emergence.

Emerger® + Artist® (flufenacet + metribuzin) on metribuzin-tolerant varieties is a popular start to weed control programmes, picking up a range of broadleaf weeds, while both aclonifen and flufenacet give extra protection against grassweeds.

When using Emerger® remember to follow our best practice application advice.

Acknowledgements

Vimoy containts isoflucypram. Proline contains prothioconazole. Iblon contains isoflucypram. Univoq contains fenpicoxamid + prothioconazole. Jessico One containts fenpicoxamid. Adepidyn contains pydiflumetofen. Ascra contains bixafen + prothioconazole + fluopyram. Elatus Era contains benzovindiflupyr + prothioconazole. Revystar contains mefentrifluconazole + fluxapyroxad. Siltra contains bixafen + prothioconazole. Aviator contains bixafen + prothioconazole. Emerger contains aclonifen. Vimoy, Proline, Iblon, Jessico One, Ascra, Siltra, Aviator and Emerger are registered trademarks of Bayer. All other brand names used are Trademarks of other manufacturers in which proprietary rights may exist.

Use plant protection products safely. Always read the label and product information before use. Pay attention to the risk indications and follow the safety precautions on the label. For further information, including contact details, visit www.cropscience.bayer.co.uk or call 0808 1969522