March vegetable agronomy update: disease risk, nutrition choices and IPM planning

Planting is gathering pace across vegetable systems. This month’s focus is on keeping disease under control in wet conditions, tightening nutrition decisions at planting, and planning ahead for spring pest pressure with fewer insecticide options available.

By Kathryn Styan, Agrii vegetable technical advisor and agronomist (Worcestershire and Gloucestershire)

Here in the Vale of Evesham, indoor salad planting is well underway. Baby leaf salads, whole head lettuce and pak choi are all moving, and with prolonged high moisture levels we are keeping a close watch for downy mildew and sclerotinia in known hotspots.

Early spring operations are also underway on asparagus, with old fern destruction and pre-cropping herbicides planned ahead of cropping in April.

Soil conditions and planting progress

As outdoor planting begins, soils are generally in good order. Last season’s prolonged dry spell gave many businesses the chance to address issues, though the wet weather since Christmas will delay planting in some areas.

Recent soil samples should guide fertiliser decisions at planting. This season, phosphate needs particular attention as pressure continues to build around responsible use and justification.

Phosphate decisions: where activators can help

Where soil analysis shows high phosphate indices, a phosphate activator can be a sound technical and cost-effective option, especially while fertiliser prices remain high.

Agrii-start Release works by increasing the availability of phosphate already in the soil, particularly in higher pH situations. Where high-index soils are identified, this approach can be a sensible fit for the season’s nutrient strategy.

Early spring nutrition: manganese, then balanced N, S and K

Manganese remains an important nutrient for early spring crop strength, helping crops cope if temperatures dip.

Once travelling becomes possible in overwintered crops, nutrition plans need to ensure adequate nitrogen, sulphur and potash are available to carry crops through to harvest without unnecessary checks in growth.

Managing disease after a wet winter

Wet conditions have made it difficult to keep fungicide programmes on track in overwintered crops. The relatively mild temperatures before Christmas also suited fungal activity, so the priority now is twofold: resolve any issues that have developed and protect new leaves as temperatures rise.

For indoor salads and known hotspots, it pays to stay alert early. Disease pressure can move quickly when humidity stays high, especially where airflow is limited.

Pest pressure is building: plan early with fewer insecticide options

Looking ahead to warmer months, pest pressure needs to be treated as a near-term priority. Last year saw high aphid infestations in late spring, so close monitoring will be important again this season.

With the loss of indoxacarb, controlling caterpillars is likely to be more challenging through spring and summer. As product choice narrows, decisions around thresholds, timing and wider impacts matter more.

IPM and beneficials: protecting what still works

As insecticide options decline, supporting beneficial insects through integrated pest management (IPM) becomes more valuable. It is also worth keeping a close eye on the wider impact of pyrethroid use, especially where repeated use can disrupt beneficial populations.

Where growers have introduced flower margins through stewardship schemes, many have seen clear benefits in reducing insecticide use. If you are considering this approach, keep an eye on the Sustainable Farming Incentive (SFI) offer for options that support pollen and nectar mixes or wildflower margins in field corners and less productive areas.

Trials focus: biologicals moving from screens into field work

In the background, spring trial planning is well underway with a strong focus on biological products. Several crop screens have been completed in the greenhouse over winter and successful candidates will move into field trials this spring and summer.

With fungal work in particular, everyone will be hoping for more rainfall than last year so trial sites reflect a wider range of disease scenarios.

What this means on farm

• Use soil samples to guide planting nutrition decisions, with particular care around phosphate strategy.
• On high-index soils, consider whether a phosphate activator is a better fit than additional phosphate.
• Plan early spring micronutrition, including manganese, alongside balanced N, S and K for overwintered crops.
• Review disease pressure after a wet winter and protect new growth as temperatures rise.
• Monitor aphids and caterpillars early and build an IPM plan that supports beneficial insects.
• Where suitable, consider margins and mixes that support beneficials and reduce reliance on insecticides.