How to tackle disease in crops with wide drilling date variation

How to manage early and late drilled wheat crops at T1

Early drilled crops are already showing high Septoria pressure. With likely higher yield potential, these crops should justify the extra spend at T1 for the more effective chemistry in Iblon® based products. For example, the Vimoy® co-packs with a prothioconazole-based partner bring a broad spectrum of disease activity, including Septoria and excellent rust control. These forward crops will also be at risk from eyespot, which both prothioconazole and isoflucypram will help against.

For the later drilled, more backward crops yellow rust is likely more of an issue. Here you might consider reducing spend and using Ascra® Xpro®, which will deal with a slightly lower Septoria risk, while being strong on yellow rust.

Variety risk obviously plays a part – hopefully slower developing varieties were drilled earlier and faster developing ones later. Those faster developing ones do tend to be a bit more susceptible to rust – for example Extase, which is a variety I’ve already seen infected by yellow rust.

With varied growth stages timing of these sprays can be tricky. Knowing drilling dates for each field and dissecting plants to find which leaf layer is emerging will help avoid incorrect timing, which should be when leaf three is most or fully emerged.

It’s also helpful to try to avoid spraying T0 fungicides too soon, as this can encourage the T1 to be applied too early. Working back a month from the expected flag leaf emergence date of the end of May means most T1 should be applied at the end of April, with T0s in early April.

Avoid tiller abortion in winter barley

The biggest response to fungicides comes at T1 (GS30/31) in winter barley, where you’re looking to maintain as many tillers as possible to maximise yields. Disease infections around this timing can cause the plant to abort tillers and once they’re gone, the plant isn’t able to compensate by producing extra grains in the way wheat can.

Generally, a good broad spectrum fungicide that has activity against all the main diseases, such as Rhynchosporium, net blotch, brown rust and mildew is a wise choice, taking into account a variety’s strengths and weaknesses. Ascra® Xpro® would make a very strong broad-spectrum option, while products including trifloxystrobin are valuable, particularly where net blotch is the major concern.

Keep on top of light leaf spot

Once oilseed rape crops reach full flowering – likely towards the latter half of April – depending on weather, most crops will benefit from a flowering fungicide spray to keep on top of light leaf spot and / or Sclerotinia.

An SDHI-based product co-formulated with an azole fungicide, such as Aviator® Xpro®, will help provide two modes of action, which is helpful particularly against light leaf spot.

For Sclerotinia the objective is to coat the petals in fungicide just before they start to drop, helping protect against infections that start when inoculum spores land on the petals. The spores use the nutrients from the petals to germinate and infect plants, typically where they have stuck onto stems after falling.

Applications usually protect crops for around three weeks, so if flowering is prolonged a second application might be required.

Build a wide spectrum potato herbicide mix at pre-emergence

It’s increasingly important to use chemistry from different groups for potato weed control, particularly for grassweed control.

Emerger® is one such building block, which has activity against grassweeds and is also strong on key broadleaf weeds, such as shepherd’s purse, volunteer oilseed rape, charlock and cleavers. Options for partner products include pendimethalin.

Pay attention to application technique when applying Emerger® - use enough water to give good coverage of the soil surface and consider using a soil adjuvant to help keep it on top of the soil profile to prolong longevity. Moisture is also important to good efficacy as with any residual herbicide.

Ideally apply within 48 hours of planting, but definitely at least seven days before the potato crop emerges.

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Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Aviator®Xpro® contains bixafen and prothioconazole. Emerger® contains aclonifen. Vimoy® contains isoflucypram.

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