With maize drilling now commencing, talk has turned to how we can maximise our yields in this spring crop.
Of crucial importance is early weed control, as competition at establishment can significantly impact yield; a problem often encountered in a continuous maize rotation where weed burden can build.
Early weed control will eliminate competition to nutrition, water and light which, when limited, can impact on the maize’s early establishment and growth.
With the loss of Calaris (mesotrione + terbuthylazine) this season, we are also faced with fewer options for post-emergence weed control, so pre-emergence chemistry may need to be considered, even if historically it has not been employed.
Pre-emergence chemistry can offer the best opportunity to control grasses and broadleaved weeds.
It can allow the crop to get off to a good clean start and also helps relieve later pressure of post-emergent timings, which may be delayed due to weather or other workload pressures at this time of year.
However, as always, the weather will ultimately dictate our chemistry strategies and, if dry conditions continue to prevail, pre-emergence chemistry will need to be carefully considered in light of dry conditions and chemistry efficacy.
In oilseed rape, flowering has been a staggered process this year, with some crops showing a scattering of yellow buds back in early March and others, some of which have been badly affected by flea beetle larval damage, taking until the middle of April to finally show their bright yellow petals.
While pollen beetle could be found in rape crops since the beginning of early spring, and levels have built to threshold levels, many crops have not been sprayed with an insecticide, due to a scattering of open flowers found in the majority of crops meaning the pollen beetles migrated away from the buds and to the open flowers, becoming pollinators rather than pests.
It is also worth noting that the lower plant populations are more branched, producing more excess flowers, resulting in higher thresholds. However, backward crops are still vulnerable to pollen beetle attack at yellow bud and, with warmer temperatures now returning, we should be vigilant to this threat.
Unfortunately, there are still a few situations arising where oilseed rape crops that have been nursed through the winter are exhibiting such bad flea beetle larvae infestation that their viability is now being questioned.
These backward crops are being held at yellow bud and, together with pollen beetle attack, they are suffering the fate of being written off still.
For crops that have flowered, sclerotinia spraying has the potential to become a protracted affair, with crops exhibiting varying growth stages within fields.
Many crops were flowering three weeks earlier than last year, meaning flowering is likely to be a prolonged affair resulting in a longer sclerotinia risk period.
Three factors are needed to contribute to the sclerotinia infection cycle – the crop being in flower, the presence of sclerotinia inoculum and warm, humid weather conditions with relative humidity over 80% and air temperature at, or over, 7degC for more than 23 hours.
Applying sclerotinia fungicides at the right time is critical for effective disease control and forecasting and disease alerts have become an important part of spray decision-making.
As sclerotinia sprays are preventative rather than curative, it is crucial that infection risk (published in weekly updates from AHDB and BASF) is taken into account, as well as the stage of the crop – and the possibility of spraying twice may need to be considered if the flowering period is long and conditions remain conducive to infection.
In winter wheat, T1 timing is looming. However, with some varieties romping away this spring and looking to be very forward, we must remember that this visual picture can be very deceptive and that the forwardness of the crop and the actual growth stage can be misaligned.
Therefore, the only way to determine if your crop is indeed ready for its T1 is to dissect the plant to determine if leaf three has fully emerged.
This timing is crucial, as it is important to keep leaf three clean to prevent septoria infection spreading up on to leaf two and eventually the flag.
It is also important to wait for this growth stage, to minimise the gap between the T1 and T2 application to no more than three weeks. T1 chemistry can be costly and protection of leaf three is crucial, so make the application count – and be sure you have hit the right leaf.