THE late spring means that new advice is available to cereal crop growers from AHDB.
Tim Isaac, AHDB's head of arable knowledge exchange, said: “Both the autumn and spring cropping seasons got off to a challenging start and crops are now racing through their growth stages.
“But, with extremes of hot and cold, crop growth has neither been smooth nor predictable this season and this makes field work hard to plan.
“The AHDB website contains a wealth of information but it can be overlooked during the busy late-spring period. So we’re reminding people to take advantage of our resources to make the most out of the 2018 crop.”
Disease management
Many people have been playing catch-up with disease control, but to determine the most appropriate time for spraying, people should view the cereal growth stage information published at cereals.ahdb.org.uk/wheatgg
Paul Gosling, AHDB's crop protection scientist, added: “In wheat crops, even if the timing interval between T1 and T2 is short, it’s vital to make sure the timing of the T2 is correct. The flag leaf should be fully emerged (GS39). Any delay in treatment increases the chance of infection.
“With hints of declining SDHI efficacy against septoria now evident in some places, it’s also important to include a multi-site at T2 to manage resistance and improve control.
“In UK barley crops, ramularia isolates with strong resistance to SDHIs are now also common and SDHIs can no longer be relied upon for control, so it’s important to include chlorothalonil at T2.”
In June, attention turns to the T3 wheat ‘ear wash’ spray to target fusarium head blight and ‘top up’ foliar disease control on the flag leaf
The decision to spray at T3 depends on many factors, including the weather and the target market, but those spraying will likely turn to azoles.
AHDB's fungicide performance work shows several are effective (epoxiconaozle, metconazole, prothioconazole and tebuconazole) but T3 sprays can select for azole-resistant septoria strains, even when septoria is not the primary target. In order to protect azole, a multi-site should also be included at T3.
Weed management
With black-grass seed heads starting to show above winter wheat crops, severe patches can be sprayed off with glyphosate.
The AHDB guidance shows spraying or cutting the crop around the first week of June can prevent viable seeds being returned to the seedbank.
Nitrogen management
Pest management
At the end of April, EU Member States endorsed proposals to extend the ban of neonicotinoid insecticide seed treatments to include wheat and barley crops.
This will put more pressure on pyrethroid chemistry, especially in the autumn. AHDB monitoring shows aphids can acquire widespread resistance to pyrethroids and the chemistry needs to be used with care, whenever in the cropping season it is used.
Several cases of pyrethroid resistance in grain aphid, from various locations, have already been reported. These can cause direct feeding damage to cereals over the summer.
Crops should be monitored and a spray considered if half of tillers are infested at the start of flowering (GS61). If pyrethroids are used, full recommended field rates must be used. If control is poor, a pyrethroid-based product should not be used again.
Although no reported resistance cases in bird cherry-oat aphid have been found, best practice must be followed to help prevent issues arising. Late-sown spring crops can be particularly susceptible to these up until GS31 (first node detectable).
There are no treatment thresholds and any bird cherry-oat aphids present should be assumed to be carrying barley yellow dwarf virus (BYDV).
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