Getting the most from your wheat crop means making smart decisions throughout the season to get the best control of threats to your yield from diseases, weeds and pests.
Posted a year ago
While concerns about a repeat of the wet autumn of 2019 did prompt some growers to drill in the latter part of September, the majority have waited until October. This delay should have allowed plenty of time to remove any crop residues and achieve stale seedbeds, with at least one pass of glyphosate, if not two. Our germination map is plotting the emergence of black-grass up and down the country, so send in your updates via social media using #BlackgrassMap.
Grower should prioritise drilling according to black-grass pressure in each field, beginning with those with the lowest pressure, and targeting fields with the highest, later. Ideally, leave fields with the biggest black-grass problem until mid-October, when the main flush of black-grass is finished. A traffic light system of red, amber, and green can help visually prioritise fields on a map.
Aim to establish between 220 and 300 plants/m2 and adjust seed rate to account for grass-weed pressure, as well as soil type. Later-drilled fields may also need higher seed rates.
To reduce black-grass chit at drilling, sow at a depth that is appropriate for your land, but minimises soil disturbance. Rolling as soon as possible after drilling will help to consolidate the seedbed, break down any remaining clods and optimise the efficacy of pre-emergence herbicides that will be applied. Rolling can also reduce slug activity under the soil.
Apply pre-em herbicides promptly, ideally 24 to 48 hours after rolling, since black-grass will start to chit as soon as the soil has been disturbed by the drill. Apply a robust pre-em, such as Liberator, to soil which has sufficient moisture. This will aid residual activity in the active weed germination zone. Even where soils are drier than ideal, apply the pre-em at the same timing, since this will still be more effective at early weed control than waiting until rain arrives, or after the crop emerges.
Proclus is a new pre-em option to aid control of black-grass. It contains a new active, aclonifen, which can only be used at pre-em and in conjunction with Liberator, but provides an additional 15% of control.
To prevent potential crop damage from residual chemistry being washed into the crop rooting zone, growers should avoid applying residual herbicides to waterlogged soil or where heavy rainfall is expected.
Avoid big pre-em stacks, even in high weed pressure situations. Splitting treatments into two timings, pre- and peri-emergence, can be more effective and also reduces the potential for crop damage.
Finally, crops that were drilled in September may be at higher risk of Barley Yellow Dwarf Virus (BYDV). Growers should monitor crops closely in October for the presence of grain aphid and bird cherry aphid, and prepare to apply an insecticide if necessary.
While many growers in the south and east have successfully got crops off fields and into barns, others are dealing with a higher proportion of later-ripening spring cereals, and a wet August, which is delaying combining and driving down crop quality.
This has led to somewhat of a north-south divide when it comes to September workloads, but the principles remain the same: focus on soil remediation and black-grass control with stale seedbeds.
The impact of last year’s wet winter should be assessed in terms of soil structure, identifying areas where ponding was observed, or where soil was damaged by machinery. Any remediation work required, including repairing or installing drains, should take place as soon as possible.
Some growers may be anxious to get crop in the ground as soon as possible, to avoid a repeat of last year’s wet winter, but delaying drilling of winter wheat until October will provide the best opportunity for early black-grass control.
Where fields have been cleared of crops, recent rain has provided a good opportunity to start stale seedbeds. Light cultivations will help chit black-grass and encourage early flushes of crop volunteers and weeds, to spray-off with glyphosate.
The timing of glyphosate sprays and application technique is important to optimise contact with fine grass-weeds, so take care to select the appropriate nozzle, water volume, and forward speed, which should be no more than 12 km/h. Control is best when weeds are at the two true leaf stage.
Where time and conditions allow, generating and spraying two flushes of weeds provides the best control of black-grass pre-drilling, and significantly reduces the pressure on residual and contact herbicides. But any more than two passes provides no significant benefit and also increases the potential to select for herbicide resistance.
There are other benefits to drilling later. With the loss of seed treatments to protect against Barley Yellow Dwarf Virus (BYDV) earlier-drilled crops will be more vulnerable to disease transmission from aphid populations in September. Waiting until October, when temperatures are lower and the aphid population cycle slows, can lessen the risk of infection.
Earlier-drilled crops are also at greater risk of Septoria, due to increased exposure to the ascospores in the autumn.
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