Agronomy pointers for the busy month of April in the north

Crop Progress

After a frustrating start to the year, March started off in a similar vein. One or two dry days were followed by a wet day, very wet in some cases, and it felt like we were back to square one.

Some fertiliser was applied at the beginning of the month, and no doubt by the time you read this, a lot more will also have received some much-needed nutrition. Hopefully, by the end of March there will have been some windows to complete post-emergence weed control sprays where needed. If not, they will be priority number one in April.

Tom’s agronomy tips for April

1. Yellow rust the key threat to consider for T0s

Yellow rust was quick to show up in some wheat varieties in early March. As well as the usual suspects that are very susceptible, it was also being found in varieties, such as Skyscraper, which are susceptible in the juvenile stage but not once adult plant resistance kicks in.

The mild winter weather, combined in some cases with later drilling, will make yellow rust a key disease this spring, I suspect, along with Septoria, particularly on more normal drilling date crops.

At T0, it’s yellow rust I would be most concerned about – look out for it on the usual susceptible varieties and in late drilled crops, which research has shown can be more susceptible, and where necessary treat with a tebuconazole-based product.

2. What’s an appropriate spend on fungicides this season?

There’s going to be a lot of discussion about what is an appropriate fungicide spend this spring. With backward crops, crops that have been under water for periods of time, as well as more forward and better looking crops, there’s a lot of variability to consider and no one size fits all approach is likely to work.

Do remember to assess what is in front of you – yield potential may have been lost in some crops already, but disease can still rob much more, so the use of appropriate rates and priced fungicides should provide a return on investment.

As this is being written there’s still a long way to go until T1 timing in wheat, so who knows what disease pressure is going to be like.

Timing T1s correctly is always a little more challenging than the flag leaf spray at T2, but this year might be even more difficult with such variability in crops. There’s going to be no substitute for dissecting crops to check whether it is final leaf three that has or is emerging – that’s what you’re aiming for. Go too early and you won’t protect it adequately, leave it too late and disease can be already infecting the leaf.

This year, Bayer has launched its new SDHI-containing Iblon® fungicide, Vimoy® (isoflucypram), which will usually be delivered in various co-packs also containing a prothioconazole-based product, such as Proline® (prothioconazole).

Vimoy is a very good all-round fungicide, performing as well as the best against yellow rust, and comparably, if not a little better, than mefentrifluconazole against Septoria. Together with strength against eyespot it makes a really good fit at T1 in a lot of situations.

A typical use rate is likely to be 1.0 L/ha Vimoy + 0.5 L/ha Proline, which with a co-pack containing two 5L cans of Vimoy and one 5L can of Proline will treat 10ha.

If disease pressure is higher, you could increase rates to 1.2 L/ha of Vimoy and 0.66 L/ha of Proline® , which will treat 8.3ha.

Where disease pressure doesn’t warrant the extra efficacy of Iblon, or cost considerations and yield potential are playing a role in decision making, the option of Ascra® (bixafen + prothioconazole + fluopyram) remains. It’s a very good fungicide in its own right and will provide decent control of the key diseases at T1.

3. Protect winter barley tillers

In a difficult year like this one, protecting winter barley tillers will be key to salvaging an acceptable yield. Winter barley yield is set by the number of viable tillers, and infections of disease around GS30/31 are well-known to cause the plant to abort tillers.

Getting some early nutrition into crops that were looking yellow and backward in February and early March will also have been important to getting them back on track, but lush growth and conducive weather is also a recipe for disease.

Those two things combined would suggest a decent fungicide at T1 will be important to help maintain yield potential. Diseases to look out for include net blotch, Rhynchosporium, mildew and brown rust – it was very easy to find the latter in hybrid barley earlier in the season.

A good broad-spectrum choice to provide control of all of these diseases would be Ascra. You can only use it once in a winter barley fungicide programme and I would suggest T1 in most cases is the best time to take advantage of that all-round disease control at the time you most need it.

The exception might be where you know Ramularia is likely to be an issue. In that case using another very good all-round option in Siltra® (bixafen + prothioconazole) at T1 and then following up at awns emerging with Ascra could be the play.

4. Is it worth spraying oilseed rape?

Oilseed rape has become the crop you don’t really want to ask about, even in our region, where it hasn’t suffered as much from cabbage stem flea beetle attacks in the past.

But more pest attacks combined with the crap weather has left many crops not looking that great, albeit there are some diamonds in the rough out there.

Growers, rightly, have been reluctant to spend too much on them up until this point, but if you do have crops that are viable to harvest, then the flowering spray for Sclerotinia and light leaf spot is worth considering.

There are forecasting systems that will help with Sclerotinia risk and, if you need to treat which in most cases is sensible risk management, then Aviator® (bixafen + prothioconazole) is a good option.

It provides good protection against Sclerotinia when applied at early to mid-flowering, just before petals begin to drop, and will also help against light leaf spot. Trials have shown that it can give a yield boost in the absence of disease through its physiological effects on the plant, which helps justify its use further.

5. New herbicide options for pulse growers

If you’re growing field beans or combining peas, there is a new herbicide option to consider, which given the shortage of products hopefully is welcome news.

Emerger® (aclonifen), which if you grow potatoes you may well be familiar with, has a label extension into field beans and combining peas. It can’t be used on vining peas however.

It is strictly pre-emergence only of the crop and works well as a mix partner for products such as Nirvana® (pendimethalin + imazamox) or Stallion® SyncTec (clomazone + pendimethalin).

Emerger will bring good activity on a wide range of broadleaf weeds and a little bit of activity against black-grass. Ideally it needs to be applied to a fine, firm seedbed and follow best practice in spray application – for example, making sure the spray tank is always kept agitated.

The product can still be used in potatoes, where it should be applied at least seven days before the potatoes emerge. Again, it makes a good mix partner for products, such as Artist® (flufenacet + metribuzin) or Sencorex® Flow (metribuzin).

6. Early season weed control in sugar beet

With the neonicotinoid seed treatment derogation being granted because of the high risk of virus yellows in sugar beet, and as importantly the weather, it’s likely to be a slightly later sugar beet drilling campaign again this season.

Weed control in the crop as ever will remain an important aspect of getting the crop growing without impediment. Getting the crop to 12-16TL when mature plant resistance kicks in against aphids transmitting virus yellows as fast as possible will remain crucial, especially in the approximately 40% of untreated crops, and is also important for yield.

Our option for conventional varieties is Betanal® Tandem® (phenmedipham + ethofumesate), which can be used up to a total maximum dose of 4.0 L/ha, usually applied in three splits of 1.0 L/ha followed by two 1.5 L/ha doses.

It’s strong on weeds such as dead nettles, speedwells, bindweed and cleavers, with more of a weakness against knotgrass and redshank. However, it will usually be used in mix with Goltix® (metamitron) which should help cover any missing weeds in the spectrum.

Acknowledgements

Iblon contains isoflucypram. Vimoy containts isoflucypram. Proline contains prothioconazole. Siltra contains bixafen + prothioconazole. Ascra contains bixafen + prothioconazole + fluopyram. Emerger contains aclonifen. Nirvana contains pendimethalin + imazamox. Stallion SyncTec contains clomazone + pendimethalin. Artist contains flufenacet + metribuzin. Sencorex Flow contains metribuzin. Betanal Tandem contains phenmedipham + ethofumesate . Goltix contains metamitron. Iblon, Vimoy, Proline, Siltra, Ascra, Emerger, Artist, Sencorex Flow and Betenal Tandem are all registered Trademarks of Bayer. All other brand names used are Trademarks of other manufacturers in which proprietary rights may exist.