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 2 years ago
Winter wheat drilling is almost complete for the majority of growers, and with one last push they will be finished before the new year, which is a better position than many were in at the end of 2019.
Attention should now turn to monitoring over December and January to ensure crops stay as clean as possible before spring.
Pre-emergence herbicides have done a very good job, in general, this season. But where it was only possible to apply at peri-emergence, some black-grass and other grass-weeds have come through.
Where grass-weeds are emerging, growers should consider applying an autumn contact herbicide such as Atlantis OD, which offers good control when applied to black-grass at up to three leaf stage. However, growers will need to watch the weather, since active growth of weeds is required for best control, and low temperatures and high rainfall will decrease efficacy. Applications may only be possible in early December unless the weather stays mild.
Slugs are now more active, so it’s important to monitor crops for evidence of grazing up to GS14 (four leaves unfolded), although crops will remain vulnerable up to GS21 (one main shoot and one tiller). Lay slug traps in the crop and treat if the number found reaches the threshold of four slugs per trap.
Checking crops for the presence of aphids should also continue, particularly where the T-Sum threshold has been reached for the second generation of wingless grain aphid and bird cherry aphids. Any pyrethroid sprays should be well-timed, to ensure control and prevent potential Barley Yellow Dwarf Virus (BYDV)transmission.
Disease levels in crops have been relatively low so far, although yellow rust has been seen in some crops and volunteers in the south and Herefordshire. Grower should monitor disease levels closely, since autumn infection levels given an early indication of what they will face in the spring.
For growers with land still to drill, soil-borne disease will pose an increased threat, so ensure all seed is treated with Redigo Pro to provide protection from a range of seed- and soil-bourne disease, including fusarium.
November presents a mixed picture for many wheat growers across the country, with some areas drilled-up, and others struggling to get crops in due to the wet weather in the latter part of October, and working around the lifting of root crops.
Though there were concerns about black-grass control by drilling early, the risk may have paid off for those that got crops sown in late September/early October, as these are generally well established. Crops drilled later in October have gone in to cloddy and sub-optimal seedbeds and have been slow to emerge and in many cases.
The soil conditions in these later crops will prove challenging for herbicides, since residual chemistry may not be able to effectively reach the seed germination zone.
Where crops are not yet drilled, the focus needs to be on patience, and learning from the mistakes of autumn 2019. Waiting for better weather windows before attempting to drill will help crop establishment and pay dividends next spring and summer, as plants will be better rooted and more resilient to stress. Rolling after drilling can help where seedbeds are poor or there are large clods, and aid residual weed control.
Where land is wet, growers should use caution around rates of pre-emergence residual herbicides, where chemistry is more likely to move down into the crop rooting zone, potentially resulting in damage.
Where crops have established well with between one and three leaves, look to top-up residual weed control with an additional 0.3l/ha of Liberator. In high grass-weed pressure situations growers may want to add additional residual actives to the stack.
However, in crops where black-grass has established despite a pre-em residual application, or where no pre-em was applied, growers should consider adding a contact herbicide to an early post-emergence residual. Atlantis OD achieves good control when applied to black-grass at up to three leaf stage.
Slug activity is increasing, so growers should keep an eye out for grain hollowing and grazing activity. Winter wheat crops are at highest risk of grazing damage up to GS14 (four leaves unfolded) and vulnerable up to GS21 (one main shoot and one tiller). Lay slug traps in the crop and treat if the number found reaches the threshold of four slugs per trap.
As autumn temperatures continue to fall, we will soon be reaching the T-Sum threshold for monitoring the presence of second generation wingless grain aphid and bird cherry aphids. Regular crop walking will be required to ensure pyrethroid sprays are well timed, to prevent potential Barley Yellow Dwarf Virus (BYDV)transmission.
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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