Syngenta Summer Autumn Guide 2020 - Page 52



GRASS WEEDS
DORMANCY AND ITS IMPACT ON WEED PRESSURE continued ...
LOW DORMANCY YEAR
HIGH DORMANCY YEAR
F reshly shed black-grass seed will
emerge rapidly where adequate
moisture is present:
• Consider previous cultivations
and assess whether ploughing
and burying this seed would be a
viable option
• Leave stubbles uncultivated to
allow seed to be predated and to
germinate. Cultivations bury seed
and induce deeper dormancy
• Use minimal tillage, keeping seed
within the top 5 cm where it can
germinate
• Delay drilling (no later than endOctober) to allow maximum weed
emergence
• Spray off any black-grass that
emerges before drilling
• Apply a robust pre-emergence
herbicide within 24-48 hours of
drilling
• If ploughing is not an option
help the seed to germinate with
shallow cultivations to get the best
stale seedbed
• Ensure the established crop is as
competitive as possible, use a
competitive cultivar and carefully
consider your seed rate, adjusting
to the soil conditions at the time of
drilling
• Longevity of herbicide efficacy
will be important so a sequenced
approach is likely to give the best
result
• Consider post-emergence
herbicide sequence 3 weeks later
2. ADAPT YOUR HERBICIDE STRATEGY
CONSIDER:
IMPLICATIONS:
•Cultivation impact on when blackgrass seed will germinate
• Drilling date
• Soil type
• Stacking vs sequencing approach
• Timing of herbicide application
52
ACTIONS
• Consider
resistance
testing if you are
unsure of the
status
• Map where you predict
grass weed seeds are
based on previous 5 year
cultivations
• Monitor weather at weed
flowering and assess
dormancy
• Adapt your cultivation
strategy accordingly
• Consider the implications
of drilling date, cultivation
strategy and soil type on
grass weed emergence
• Adapt your herbicide
strategy accordingly
• As a guide, aim to apply
pre-em within 48 hours
of drilling; apply sequence
3 weeks later. Adequate
soil moisture is important
for good performance of
residual chemistry

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