Disease pressure building after prolonged wet weather

After weeks of saturated soils and prolonged leaf wetness, Scottish cereal crops are carrying strong potential, but also a rising level of disease risk.

Winter crops generally established well in the autumn, with many drilled by the end of September and some going in at the start of the month. That has left a lot of crops looking full of promise, with strong biomass and good yield potential. However, the same conditions have also created an environment where disease can build quickly as spring approaches.

In winter barley, rhynchosporium is already being seen at significant levels in two-row varieties, while brown rust is present in hybrid barley crops. Both will need close attention early in the season to avoid disease becoming more difficult to manage.

In wheat, yellow rust remains a key concern. Active yellow rust has been seen in crops since the end of December. Although some infections appeared to ease through the colder period, the early presence of disease means growers should be prepared for it to return as temperatures rise.

Yellow rust is being seen across a range of varieties, including some of the most widely grown wheats in the area. Bamford, which is popular due to its end-market opportunities, is showing notable levels of infection. Yellow rust is also being seen in Hexton, which many growers moved into last year and which does not carry the Yr15 resistance gene.

Septoria and stem-based disease also need watching

While yellow rust is the more visible concern in some crops, Septoria should not be underestimated.

Many early-drilled wheat crops are carrying a significant amount of Septoria in the lower canopy. With strong crop growth and plenty of leaf material present, there is potential for disease to move up the plant if wet conditions continue into spring.

Stem-based disease is also a consideration, particularly in earlier drilled second wheats that have spent several weeks in waterlogged soils. These crops should be monitored carefully as fields become trafficable and spring assessments begin.

Fungicide programmes may need a more flexible approach

This spring, fungicide timing may not be straightforward. Sprayer capacity is likely to be one of the biggest practical challenges, particularly where herbicide, plant growth regulator and fungicide applications all need to be fitted into a narrow weather window.

Where brome or Italian ryegrass still needs to be controlled, product choice becomes more complicated. In some situations, tebuconazole may not be suitable to include with herbicide applications because of crop safety concerns.

A strobilurin may be an option for early rust activity, but this needs careful thought. With only two strobilurin applications permitted per crop, using one early could limit flexibility later in the season if yellow rust remains a persistent issue. Labels must also be checked to ensure the product can be used in the intended way.

In some cases, it may mean two separate passes are required, conditions allowing. One pass may be needed for herbicide, followed by another with a PGR and fungicide to manage lush growth and disease risk.

Because Septoria and yellow rust develop at different speeds, especially in more susceptible varieties following the breakdown of Yr15, traditional fungicide timings may need to be treated with some flexibility. T0 decisions should be based on crop condition, disease levels, variety risk and the weather forecast closer to application.

Root health and nutrient uptake after waterlogging

Despite the wet conditions, many crops have coped surprisingly well, helped by the strength of autumn establishment. However, waterlogging can still affect root function and nutrient uptake, especially on lighter soils and in more vulnerable fields.

First nitrogen applications on wheat are likely to be due soon where conditions allow. Alongside this, manganese and copper deficiency are now showing in a number of crops, particularly on lighter land with a known history of manganese deficiency.

These deficiencies should be addressed once fields are fit to travel. Zinc may also have a role where rooting support is needed, particularly in crops recovering from waterlogged conditions.

Residual herbicides have performed better than expected

Autumn residual herbicides appear to have worked surprisingly well, despite the earlier drilling window. Strong, thick crops have helped by smothering surviving weeds through the mild back end of the year.

Some spring follow-up herbicides will still be needed, but the overall requirement may be lower than in more difficult seasons. Current expectations suggest around 10-20% of crops may need a spring follow-up, compared with 40-50% in some years.

That said, individual field assessment remains important, especially where grassweed pressure is known to be high or autumn control was compromised.

Strong crop potential, but careful decisions needed

The overall picture is one of promise, but also risk.

Many crops have strong yield potential, but disease pressure is already present and spring management will require careful judgement. With current grain prices, there will naturally be pressure to scrutinise input spend. However, cutting back too far can become a false economy where yield potential is already in the crop.

This spring is likely to be a balancing act between protecting margin and protecting yield. Decisions should be made field by field, taking account of variety, drilling date, disease pressure, crop biomass, soil conditions and the practicalities of getting applications on at the right time.

For growers in Scotland, the priority now is to keep crops under close review and be ready to act when conditions allow.