The cool spell has slowed both crop and disease development. Mildew is insignificant in wheat and rust mostly checked (except brown rust in Crusoe), whilst septoria levels remain high. T0 has been largely completed, protecting leaf 4 from infection.
Warmer weather, following the first main top dressing, will see cereals romp through the growth stages. No matter how slowly spring gets “sprung”, we’re usually at flag leaf by 20 May, and T1 by 25 April.
Oilseed rape is mostly into early flowering except where it’s being badly pigeon grazed. Significant numbers of pollen beetle are about, but will only threaten backward crops. Once flowers open the beetles do more good than harm as pollinators. Light leaf spot remains very active dependent on variety and topography (and whether pigeons have left any leaf).
In some varieties, the early flowering treatment will need to cover light leaf spot and sclerotinia, with activity against alternaria, botrytis and powdery mildew also desirable. A co-formulation of prothioconazole and fluopyram fits the remit well. In others, azoxystrobin mixed with a triazole or thiophanate-methyl will cover sclerotinia, aid green leaf/pod retention and add some verticillium activity.
On heavier land farms, spring beans and peas remain in the shed. Soil temperatures are low and the ground wet, so no panic yet. Weevil notching has started, so monitor emerging spring crops closely, treating if needed. The odd spot of rust and mildew are active in winter beans, but below treatment thresholds.
With crop values low, scrutinise inputs carefully. Use adjuvants where they are needed. Water conditioners can have a big impact on the activity of products as diverse as pyrethroids, glyphosate and sulfonylurea herbicides. But test your water source before you spend – I work in one of the hardest water areas in the UK, but that isn’t the case for everyone.
Continuing my intention to remain positive about the weather – the showers which have followed the drilling and planting of spring cereals, beans and potatoes have consolidated seed-beds and ridges nicely in advance of any pre-emergence herbicides. Be wary of cutting water rates with these, particularly if linuron is involved, as this has a statutory minimum of 300litres/ha.
Overwintered aphid populations are now be on the move and, with barley yellow dwarf virus (BYDV) patches noticeable in winter crops, be sure to monitor spring cereals closely and treat where needed.