Disease and insect pest control advice for Midlands growers in May

1) How to approach late T1s in wheat

Most wheat T1s, hopefully, will have been applied by the time this is published, but for some later drilled crops or if the weather has gone against spraying, there could still be some to apply.

If the weather has remained mostly dry, and disease pressure, especially from Septoria, remains low that would suggest a lower spend at T1 is possible. Yield potential in these crops, likely late drilled, will also be lower, although disease still needs controlling.

In this situation, Ascra® Xpro® fits – providing good all-round disease control and also some useful physiological benefits from the SDHI active substances, such as improving rooting, chlorophyll production and tiller retention.

Where rust is a greater concern, then there could also a case for using one of the isoflucypram-containing options, such as Plaxium® or Vimoy® plus partner to take advantage of the excellent rust activity of isoflucypram, although they will add to cost.

If weather has turned wetter and Septoria threat levels have increased, those products are also decent choices to give broad spectrum disease control.

2) Working through the flag leaf fungicide choices

Writing this in April makes it impossible to know how the weather will have impacted disease pressure for flag leaf fungicides. So, let’s work through some scenarios.

If it has stayed dry and you have later drilled crops with potentially lower yield potential, then Ascra® Xpro® at 1.2 L/ha is a viable option to continue to keep the crop free of disease at a cost-effective price.

Earlier drilled crops with higher yield potential, where the weather has been less conducive to Septoria, and either brown or yellow rust is the main perceived threat, could justify the extra cost of Plaxium® or a Vimoy® plus partner. These crops likely don’t justify the Septoria-focused activity of either Miravis® Plus or Univoq®, where you likely need to add an additional active for brown rust control.

If the weather has turned wet and Septoria has become a bigger threat, then along with the aforementioned Miravis® Plus® or Univoq^TM options, our fenpicoxamid-containing Jessico® One in mix with Vimoy® is an excellent option for higher disease pressure situations.

3) Place for Ascra® Xpro® at awns emerging in winter barley?

Disease pressure in winter barley has reduced with the dry weather, which could lessen justification for the higher spend at T2 with the likes of Miravis® Plus.

If you didn’t use Ascra® Xpro® as your T1 choice, it could have a place at T2. Combined with good foliar disease control, the fluopyram in the product helps out against Ramularia, while the two SDHI active ingredients also provide physiological benefits as in wheat. Remember Ascra® Xpro® can only be used once in barley fungicide programmes, unlike in wheat where you can apply two applications.

4) Two spray strategy for spring barley disease control

We’re in a very different position to last year with spring barley. By mid-April last year, only 50-60% had been drilled, whereas it is pretty much all in this season. It is dry, so depending on cultivation and establishment techniques, emergence and growth is slower, especially where moisture has dissipated. Walking some fields this week, nitrogen prills were still visible so nutrition uptake is likely to be slow until we get some rain.

At this stage, I would suggest a two-spray fungicide strategy is likely to be best, especially if growth remains steady. In barley, maintaining tiller numbers is important for yield, which means keeping on top of disease to avoid tiller abortion.

Both Ascra® Xpro® and Siltra® Xpro® remain excellent cost-effective spring barley fungicides. If disease pressure is low that could offer the opportunity to use Siltra® Xpro® as the first spray, and then Ascra® Xpro® with its additional Ramularia activity at the later timing.

5) How to use new insecticide for virus control in sugar beet (& potatoes)

While dry weather, and seed deliveries, allowed sugar beet drilling to happen much earlier than in the previous couple of seasons, it could also have slowed crop growth.

That’s important with adult plant resistance to virus yellows beginning to kick in at 12 true leaves, meaning it is a race against time to reach that stage before aphids carrying the virus start landing and proliferating in crops.

The Rothamsted Research forecast suggests that aphids are expected to begin migrating in mid-May, although warmer weather could pull migration forward. BBRO’s Aphid Watch network is live from 1 May to provide twice weekly updates.

As things stand, I would think two foliar insecticide sprays might be needed this season.

Bayer has a new option in Sivanto® Prime to add to the existing approved products of Teppeki and Insyst. Sivanto® Prime contains flupyradifurone and works through contact and translaminar activity.

Given it must be applied to the crop no later than the 9 true leaf stage, plus its contact-acting mode of action giving quick knockdown, it is best used as the first spray in a programme. It also has a favourable beneficial insect profile, again adding to its suitability as a first spray. Thresholds for insecticide use remain one aphid per four plants up to 12 true leaves, or one aphid per plant from 12 to 16 true leaves.

It belongs to the chemically distinct butenolide class of insecticides and best practice would to be follow with a product from another distinct chemical group.

Sivanto® Prime also has a place for controlling aphids that spread viruses in potatoes. Again, with knockdown activity it’s best used earlier in the programme – it can be used from 10% emergence through to 13 July.

6) Think about blight programme construction

While the EU_36 strain of potato late blight remains dominant across England, two instances of EU_46 which have developed resistance to OSBPI fungicides such as Zorvec® in Europe were found in the UK late last season.

That continues to highlight the need to alternate and mix different modes of action throughout blight programmes, which needs planning as there are restrictions on the numbers of applications of various products or modes of action. In addition, with mancozeb in a use-up period and not available to buy that will add further complications to building effective programmes.

Neither active in Infinito® - propamocarb and fluopicolide – have any known resistance issues, but it can only be used a maximum of four times during the season. One of its strengths is activity against zoospores that cause tuber blight, which suggests that at least one and maybe two applications should be saved for the end of the programme.

But it can also be used earlier in programmes, around tuber initiation and with no known resistance, provides a particularly good foundation to start programmes, as well as an option during the stable canopy phase.

That wide use period is a good reason why it is important to plan in advance when you want to apply Infinito® to help get the best from an important product.

-----

Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Infinito® contains fluopicolide and propamocarb. Insyst® contains acetamiprid. Jessico® One contains fenpicoxamid. Miravis® Plus contains pydiflumetofen. Plaxium® contains isoflucypram, fluopyram and prothioconazole. Siltra® Xpro® contains bixafen and prothioconazole. Sivanto® Prime contains flupyradifurone. Teppeki® contains flonicamid. Univoq^TM contains fenpicoxamid and prothioconazole. Vimoy® contains isoflucypram. Zorvec® contains oxathiapiprolin.

Ascra®, Infinito®, Jessico®, Plaxium®, Siltra®, Sivanto®, Vimoy® and Xpro® 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. © Bayer CropScience Limited 2025