Disease remains the mist widespread threat to the UK winter wheat
crop, although black grass pressures are high in some areas with heavier soils,
while dryness is also emerging as a threat in the east too.
The Adas crop consultancy, in a monthly briefing on UK
grains, restated a caution of "high" levels of some diseases, notably Septoria,
a fungus which has been known to cause crop losses of 50%.
"Most crops [have] symptoms present on the lower leaves,"
with the outbreak encouraged by the mild winter.
"Showery conditions through April in many parts of the
country have spread the disease up the canopy of the crop, with symptoms appearing
where fungicides have been delayed."
In areas which have missed out on fungicides "yellow rust
infection remains high" too, Adas said, referring to a rust which can also
cause heavy yield losses in susceptible wheat varieties.
"It is not just the susceptible [wheat] varieties that have
been affected there are a number of varieties with higher rust resistance
scores that have also shown symptoms."
In fact, last month saw below-average rainfall overall,
although this reflected in the main weak levels of precipitation in Yorkshire,
the East Midlands and the Eastern region.
Indeed, the low rainfall" in certain regions has led to a soil
moisture deficit of 50mm [2 inches] in the Eastern region and 33 mm in the East
Midlands", Adas said, if adding that "conditions are not as dry as the spring
of 2011 when the majority of the country was suffering from drought".
The dryness has led to soil cracking which has required
extra cultivations to create a seedbed in areas allocated for spring plantings,
"adding to costs whilst increasing moisture loss".
"Spring crop seed beds in the east are very dry, which is
affecting crop germination and establishment especially on heavier soil types,
leading to uneven germination and low plant populations in some fields."
'No in-crop control
Adas also cited black grass – which competes with grains,
and is becoming increasingly resistant to specialist herbicides - as a problem
for winter wheat crops, particularly those on heavier soils in southern areas.
"In most crops there are no in-crop control options left for
this weed, with crop growth stage now beyond that allowed on herbicide labels,"
Tackling black grass stage at this stage of the season will
require targeted spraying with generalist herbicides, such as glyphosates, "in
order to reduce seed return", if at expense of some the wheat crop too.