East: Spring crop pre-em herbicides need some rain

The recent run of fine weather has allowed much of the spring cropping to be planted into good conditions and fertiliser to be applied. Spring crops where pre-emergence herbicides have been applied are now in need of a warm rain to ensure good crop establishment and enable the herbicides to work effectively.

Following the night frosts a week or two ago, grassweed herbicide applications were delayed until more consistent warm weather was experienced and we could see weeds starting to grow, but it is too early to tell what level of control we have achieved. However, changes to rotations, delayed drilling and high residual doses in the autumn has certainly reduced the amount of blackgrass emerging.

The dry and cool weather has certainly helped to reduce the disease pressure, with septoria less likely to develop onto new growth during the dry weather. The early drilled wheat is at GS30 and varieties with good rust resistance will generally receive a chlorothalonil treatment to protect against septoria, plus a plant growth regulator (PGR). With the dry and warm conditions rust is more of a focus and there are signs of rust on varieties such as Santiago, which are the priority for treatment with a mix of either tebuconazole or cyproconazole plus chlorothalonil.

Winter beans have established well and are generally clean and as spring beans start to emerge we will be watching for weevil damage and treating accordingly.

The main concern for some parts of oilseed rape fields currently is the number of cabbage stem flea beetle (CSFB) larvae in the plant. Following a dose of fertiliser most OSR crops are growing away well, but in some fields and in some patches of fields the crop has gone backward due to the larvae feeding inside the plant. Some plants are carrying up to 15 larvae, causing the side branches and the growing point to die and rot the top of the plant. In most crops the affected plants are scattered across a field with enough good plants to make a crop but in some cases, following pigeon damage, the viability of crops is questionable. It also appears to be very much soil type and soil nutrition affected as well, with more fertile fields able to put on new growth ahead of the larvae, but lighter chalky soils and low fertility areas are suffering the most.

Considering the lifecycle of CSFB, they could continue feeding until April or even May prior to returning to the soil to pupate. If the migration of the larvae to the soil happens early enough then there may be some time for the crop to put out new side branches. However, with no effective control options for CSFB currently available, in some areas the viability of OSR is even more questionable now than it was before.

See more