Maximise crop potential using these seven pieces of guidance

Crop Progress

Spring crops were starting to be drilled after land dried up in March following the February storms.

Wheat had reached late tillering toward the end of March. There’s been quite a bit of mildew, Septoria, and spots of yellow rust in certain varieties.

Oilseed rape crops looked pretty clean, although some have been hit by pigeons or cabbage stem flea beetle depending on location.

Tom’s agronomy tips for April

1. Target yellow rust at T0 in wheat crops

By the time you read this T0s will be due or already going on in early April as crops reach GS30 or leaf four emergence.

Target yellow rust at this timing, as there isn’t really any economic benefit from controlling Septoria at this timing. Yellow rust cycles very quickly, and you don’t know when the adult plant resistance, if a variety has it, will kick in so it helps to have a clean start for T1.

Choosing varieties with juvenile plant resistance to yellow rust might be a way of saving costs, as these are much less likely to be need treating at T0.

A rust-active azole, perhaps with a strobilurin where you want to increase protection on varieties with low yellow rust resistance scores, will be the logical choice where you do need to spray. A mildewicide, such as cyflufenamid, might also be necessary if you need some kickback on that disease.

2. Accurately identify full leaf three emergence for T1s

Protecting the plant from the bottom up, particularly with high commodity prices albeit combined with high fertiliser costs, will be as important as ever this season.

GS31/32 is often talked about as the timing for T1 sprays, but it’s actually when leaf three is three-quarters to fully emerged. That can coincide with GS31/32, but not always, so the only way to find out is by dissecting plants and counting leaf layers.

The fungicide needs to be applied as a protectant, before infection on that leaf, and getting it wrong will compromise disease control prior to the flag leaf spray, and setting yourself up to spend more money at that timing fighting infections and probably achieving poorer control.

We have two great options for this timing in Aviator (bixafen + prothioconazole) and Ascra (bixafen + fluopyram + prothioconazole). Choose your product depending on variety, drilling date and weather. 

The high prothioconazole loading in Aviator has a place where eyespot and fusarium are a particular risk, while in higher foliar disease pressure, especially Septoria, Ascra at 1.0-1.2 L/ha is a better choice. The extra SDHI in the formulation, fluopyram, helps act on different strains of Septoria as there is an incomplete cross-resistance profile between it and bixafen.

Both will give good control of yellow rust giving a broad spectrum of activity.

3. Preserve tillers with T1 winter barley sprays

In winter barley, you’re not looking for a specific leaf layer as in wheat for T1 fungicides, so GS30/31 is a good indicator for when to spray, but it should be before the stems start to rapidly extend (GS32).

It’s the most important disease control spray for the crop – it preserves tillers and maximising ear numbers which is the key to high yields.

Ascra is now approved for winter and spring barley, including malting crops, up until GS61, making it a one-can solution for wheat or barley. It has both physiological and disease control benefits for the crop.

But you can only use it once in the crop, so in winter barley I think its best position is at T1 as that timing usually provides the best return on investment. Ascra (0.9 L/ha) will give an uplift in Rhynchosporium and net blotch control over Siltra (bixafen + prothioconazole), while also covering brown rust and mildew.

That broad spectrum activity is important as we don’t have the resistance profiles in barley varieties that we do in wheat – there’s no standout variety for disease resistance like Extase or Theodore.

Alternatively, Siltra (bixafen + prothioconazole) at 0.6 L/ha could be used at T1, if Ramularia is the major risk, leaving Ascra for the T2 (GS37-49) with the optimum awns emerging “paint brush” timing, where it will help improve the consistency of Ramularia control.

4. Consider a two spray strategy for spring barley disease control

Spring barley crops drilled in March could be due for their first fungicide spray in April, depending on growth and strategy. Again with high prices and a reducing difference in achievable yields compared with winter barley it is a crop worth protecting in my opinion. Like winter barley, protection against Rhynchosporium and net blotch is critical – don’t rely on curative activity. A single fungicide application can be risky if the weather turns and sprayers are unable to travel, leaving the crop completely unprotected.

If you’re going for a two-spray programme, then the T1 needs to be earlier than in winter barley at GS25-30 as the crop goes through growth stages quickly, while the T2 remains an awns emerging spray.

If ramularia is the main threat, I would suggest leaving Ascra at 0.7 L/ha for the latter timing leaving Siltra at the lower rate of 0.4 L/ha at T1.

5. Consider use latent disease testing to check disease levels

Our CropCheck service will be available this spring for growers to sample wheat or barley leaves for a PCR test for key diseases, which shows the level of DNA in leaves before visual symptoms can be seen.

It’s a diagnostic tool, not a predictive one for Septoria and yellow rust in wheat, and Rhynchosporium and net blotch in barley, to give a snapshot of disease in a leaf layer to help you understand whether you’re in a more protectant or curative situation.

It should be used in conjunction with the other usual factors, such as weather, drilling date, variety and visual observations to help decide product choice, product rates and help prioritise fields or particular varieties.

6. Watch out for Sclerotinia in oilseed rape

Many growers will be looking to apply a flowering spray to oilseed rape. It’s both an insurance against Sclerotinia, which, while it doesn’t appear every year but can be very yield-robbing, and late light leaf spot.

At current crop prices it is going to be worth protecting against these diseases.

Timing is important – current fungicides only have protectant activity against Sclerotinia and light leaf spot. Optimum timing is mid-flowering on the main raceme with the idea to coat the majority of petals before any significant petal fall occurs. Petals adhering to the plant opens the way for Sclerotinia infection in the stem.

Aviator (bixafen + prothioconazole) at 0.75 L/ha provide around three weeks protection. If flowering persists for longer than that you many need a follow up spray.

Aviator’s Leafshield formulation is proven to spread droplets on waxy leaves, aids fast droplet spreading, and dries quickly which is helpful in catchy conditions.

7. Protect potato crops from PCN and weeds

With potato planting underway in April, the last part of an integrated approach to controlling potato cyst nematodes will be the application of a nematicide.

Our low-dose liquid nematicide Velum Prime (fluopyram) plays an important role in integrated management. It provides good yield protection and population management of both key PCN species – Globodera pallida and Globodera rostochiensis.

Where there’s lower pressure it can be used alone, but in higher risk it’s better to use it in conjunction with 15-30 kg/ha nemathorin.

In trials there has been no difference between in-furrow applications at planting, or an overall broadcast spray that needs to be incorporated. Choose the technique that fits best on your farm, but apply the overall spray after the de-stoning operation, incorporate to 10-30cm depth within 72 hours of when you intend to plant.

Velum is also approved for the suppression of parasitic nematodes in carrots.

Timing is also important for pre-emergence weed control with Emerger (aclonifen) needing to be applied at least seven days before the potato crop emerges.

Aclonifen has excellent activity on Polygonum, Chenopodium and brasscias species and also contributes to grass weed control. It’s predominantly taken up through emerging shoots and seems to be less effected in dry conditions when soil moisture is limited than other products.

Emerger (1.75 L/ha) can be tank mixed with a range of herbicides and can be applied to all soil types. For metribuzin tolerant varieties and appropriate soil types, Emerger partnered with Artist (flufenacet + metribuzin) is a good broad-spectrum mix, especially where you need extra grass weed activity.