College of Agriculture, Food and Rural Enterprise (CAFRE) agronomist Leigh McLean is advising the use of stale seed beds to get on top of grass weeds over the coming weeks.
This opportunity is a direct consequence of this year’s early cereal harvest.
“Light cultivation after harvest encourages a flush of weeds which can be burnt off before ploughing and drilling,” he explained.
“Where grass weeds are known to be a problem, delay drilling if conditions allow and use high seed rates to help the crop smother out unwanted grasses.
“If the grass weed burden is severe and could impacts yields, growers should consider spring cropping. This allows multiple opportunities to cultivate, chit and spray off weeds, thereby reducing the weed seed bank.”
Weeds and disease
Turning to the challenge of Barley Yellow Dwarf Virus (BYDV), McLean confirmed that earlier sown crops are the greatest risk of infection.
Research has shown that infection by migrating winged aphids is the most common route for BYDV to become established in autumn cereals.
As a consequence, growers should remove the ‘green bridge’ for wingless aphids by burning off 7-10 days before ploughing or waiting 14 days between ploughing and sowing.
As autumn progresses aphid migration and consequent BYDV infection, pressure diminishes.
However, growers should balance this benefit against the fact that later sowing means slower emergence and potentially poorer establishment.
The CAFRE representative further explained: “Only apply pyrethroid sprays when aphid colonies, not individual aphids, are present on leaves, to slow development of pyrethroid resistance.
“A few winter barley varieties show tolerance to BYDV, meaning if infected, suffer less of a yield penalty in severe outbreaks than non-tolerant varieties.
“Small quantities of tolerant seed are available this autumn so these should be considered for early sown, high-risk situations,” he added.
Given the recent rains, slugs could pose a real problem in autumn-drilled cereal crops over the coming weeks. Farmers should assess slug numbers before crops are sown.
It’s a case of setting traps on damp soil using dry bait under a tea tray sized cover.
The traps should be left overnight and checked for slugs the next day.
According to McLean, removing green cover reduces their habitat and feed source.
If slug numbers exceed four per trap in cereals, or one per trap in oilseed rape, farmers should consider applying ferric phosphate-based pellets, if emerging crops are still at risk.
