Most winter wheat crops are now flowering, and unlike some winter barley crops remain standing after the very heavy showers over the last couple of weeks.

Leaves 1 (the flag leaf), 2 and 3 on most are clean, but Septoria is present further down the plant, and with a return to a more unsettled weather pattern, has the potential to move upwards very quickly. And as flowering gets underway, late ear diseases require consideration and effective control. With approximately six weeks of growing, and grain fill still to happen before the beginning of senescence and ripening, late season disease control is essential.

The final spray timing in wheat, applied to the ear, is still based on effective azole chemistry in order to reduce the risk of Fusarium and mycotoxins, continue to control Septoria, and an important timing to retain green leaf to maximise both grain yield and bushel weight. Timing is key especially when there is the threat of rain splash during flowering, and if rain is likely, has to be during early to mid-flowering. Tebuconazole is the most effective triazole for Fusarium and is an important component of any mix at this time. Prothioconazole remains important too, continuing to suppress Septoria activity, and is also effective on mycotoxins.

Good grain fill is totally dependent on retaining green leaf area for as long as possible and the strobilurin extends this, and strengthens the Yellow Rust and Fusarium activity. ADHB trials continue to show pyraclostrobin (COMET) to be the strongest rated strob for use in wheat at this time.

Aphids in cereals

Though virus transmission is no longer an issue in winter cereals, once grain-fill begins, aphid feeding may become an issue once more, and control may be necessary. During grain-fill they colonise the ear and feed at the base of the developing pickles, drawing off the plant sugars that should be filling the grain. Growers should monitor crops regularly for aphid colonies right up to early milky ripe stage (GS73) in barley, late milky ripe (GS77) in wheat on warm sunny days, and consider control if colonies can be found on more than 50% of plants. Any less than 50% and they are unlikely to pose any economic threat.

Look out also for ladybirds. These are very effective aphid predators and if also present, then hold off on any aphicide as they are voracious feeders of these insects.

Control during grain-fill

Grain aphid, bird cherry-oat aphid and rose-grain aphid are the main aphid pests of cereals in the UK and Ireland. As well as being the same vectors of BYDV back at the early tillering stages, the same species of aphids all are also capable of direct feeding damage during grain-fill. Of these, some populations of grain aphid in certain geographical regions are becoming moderately resistant to pyrethroid insecticides, including DECIS PROTECH and STEALTH. Whilst pyrethroid resistance does not yet appear to be an issue locally, it is essential all the same to maximise efficacy and to protect these insecticides from resistance, and therefore essential to follow best practice using IPM programmes: adhere to population thresholds to assess the need for applying an insecticide. Where aphids numbers are below thresholds, avoid spraying and if required, use full rates when doing so.

In addition, any insecticide application at this time of the year is not bee friendly. Check for aphid predators such as ladybirds and hoverflies, which often do a good job of reducing aphid numbers without the need for an insecticide to be applied. If still necessary, only spray in the evening when bees are less likely to be foraging.

The cereal leaf beetle has become more apparent in recent years at this time of the season.

Its larvae are little slug-like black shiny blobs, the adult a 5mm long beetle with black head, red thorax, blue/green metallic coloured wing cases and red/orange legs. Both larva and adult feed between the veins on the upper leaves, striping out thin conspicuous stripes along the leaf. Though becoming more prevalent, they are very rarely of economic importance, and predation by other fauna keeps them in check.