East: High numbers of aphids threaten cereal crops

Cereal drilling has been progressing well into some very good seed-beds and although the recent wet weather has slowed progress, it has been readily received by very dry soils. Early drilled wheat had the dilemma of “to pre-em or not to pre-em”. However, the thought of applying residuals to emerged blackgrass was of greater concern than applying them to dry seed-beds, so they were applied pre-emergence. Now we have received some moisture it is clear to see the early applied residuals are working, but the level of control is still to be determined, with some blackgrass beyond 1-leaf when the rain arrived!

The early drilled wheat is now at GS13, with blackgrass not far behind in some cases. Any delay to drilling has been counteracted by the dry conditions and therefore stale seed-beds during September produced little weed emergence. However, where drilling has been delayed into October and stubbles were scratched, rolled and received rain the amount of blackgrass germinating and being controlled is very reassuring, with at least two good flushes of blackgrass being destroyed prior to drilling.

High numbers of bird cherry-oat aphids have been caught in the Rothamstead Research suction traps and with aphids being found in the field, any non-Deter (clothianidin) treated crops will be a priority for an insecticide soon after emergence. Where Deter seed treatments have been used then we have approximately six weeks protection, but if mild conditions continue a follow up aphicide will be required.

Oilseed rape crops are very variable, from 10 leaves and knee height to still struggling to grow away from the flea beetle damage. In those where we lost the battle against the flea beetle, the decisions on what crop to re-drill in its place is further complicated by still having to satisfy the three crop rule.

Crops that have the survived the cabbage stem flea beetle (CSFB) are by no means out of the woods. As the surviving CSFB adults lay their eggs at the base of the plant, the larvae will emerge over the next few months if mild and continue to emerge into the spring, feeding in the leaf petioles of the crop and below the growing point (see below).


Phoma levels are still low, although rain this week will certainly increase the presence of the disease in the more susceptible varieties and smaller crops are being prioritised for fungicides. Aphids can also be found in crops and with the threat of turnip yellows virus, an aphicide should also be considered where aphids are present.

Winter bean drilling will commence once the land dries up. However, good seed-bed conditions are paramount for effective residual herbicides, good germination and crop competition. Bean seed test results have indicated some samples with high stem nematode levels and should not be planted. Also, germination has been quite variable therefore seed rates will be adjusted accordingly.

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