East: Virus-carrying aphids continue to migrate

Cereal crops drilled during this season’s main drilling window (early October) are now emerging and most are establishing well. Now is a good time to drill “delayed” wheats where blackgrass is a challenge. However, many of these have been drilled as growers feared wet days ahead and took the opportunity to get the crop in the ground. Time will reveal the wisdom of this decision.

Slugs are still very active in some cereals, but as crops establish damage is more confined to the slower growing, cloddy and trashy areas. As conditions become cooler and wet, ferric phosphate based pellets will become the best choice, with more activity and being safer to the environment than those based on metaldehyde. These pellets work by stopping the slugs feeding, so there is no satisfaction of finding slime trails and dead slugs, but grazing will stop and slowly the crop will improve.

Aphid vectors of barley yellow dwar virus (BYDV) – mainly the bird cherry-oat aphid – continue to migrate. Non-Deter (clothianidin) treated crops will need protection at the 2-leaf stage and previously treated early drilled crops will need a follow up spray to maintain protection until the migration tails off. Mid-September sown Deter-treated crops may also require a top up with foliar treatment 8-10 weeks after drilling if aphids continue to migrate in mild conditions.

On fields prone to manganese deficiency (light, organic and puffy) now is time to apply foliar manganese nutrition to improve winter hardiness. As crops establish some are starting to show deficiency symptoms.

Blackgrass is already emerging in some wheats drilled in early October, particularly where pre-emergence herbicides were delayed due to wet conditions or busy workloads. In “difficult” blackgrass situations many crops have received large herbicide “stacks” and sequences; this and the slightly later drilling date may lead to fewer post-emergence contact applications (for example, Atlantis or Unite) this autumn? However, where autumn post-emergence contacts are required, they should be completed whilst the weed is still actively growing. Results can be disappointing if applied when the plant is on verge of shutting down.  Remember the usual mantra regarding the importance of good application techniques and spray times that enable the spray to dry on the leaf before the evening dew settles.

In rapeseed, propyzamide (e.g. Kerb Flo) is more effective when applied in cool conditions as this improves its persistence and weeds are more easily controlled when their growth is less active, but not entirely shut down. Firm seed-beds, high soil moisture content and recent frosts also improve the efficacy of these actives. Reports show that soil temperatures are cooling, hold your nerve a little longer and stall Propyzamide applications until soils cool to approx. 10Cor below at 30cm depth (current temperatures are approx. 12C).

Phoma is now developing quickly in previously untreated crops, so any outstanding fungicide treatments should be applied soon. In crops where phoma threshold has not yet occurred, a latent infection will be developing within the plant. In these cases a pragmatic approach to control is advised by, for example, mixing the fungicide with a scheduled propyzamide application for grassweed control. Earlier treatments will also require a robust top up for phoma and light leaf spot, for example, Proline (prothioconazole) or Refinzar (picoxystobin + penthiopyrad).

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