East: Leaf miner damage in sugar beet high

The difference between beet crops planted early into moisture or later into a dry April seed-bed is still marked. Thankfully in this part of the world the majority were in early, have never looked back, and have now fully covered the ground. Dry conditions seem to have reduced mobility and therefore efficacy of neonicotinoid seed treatments, with more leaf miner damage than usual apparent at this stage. Check for eggs on the undersides of leaves for an indication of the pressure crops may be under and to allow the planning of an insecticide, tank mix with fungicide applications.

Timing of the first fungicide in beet will, as always, be a balancing act – application before the 10-leaf stage can have a detrimental effect on yield – however, there can be a yield benefit from applying before disease is present in the crop. Black bean aphid can be found hidden in the centres of many plants, but colonies will tend to collapse with the aid of natural predators, so the decision to apply an insecticide should only be made if the crop is weak and feeding  pressure high.

Pressure from black bean aphid is certainly higher than it has been for several years in bean crops (see right). Some have required two insecticides to control the large numbers of colonies; application can also be an opportunity to target bruchid beetle if the timings come together. At this stage, crops that have received a programme of magnesium and manganese treatments stand out as looking particularly well. Downy mildew remains a threat; bear in mind that spring crops are more susceptible and that the disease can suddenly appear even at this later stage. image1

Our vining pea crops have generally not required any post-emergence weed control, despite conditions not being particularly favourable for pre-em efficacy. Some crops have had an early insecticide due to incredibly high populations of pea aphid.

Whilst it can be convenient to apply pod sealant materials to oilseed rape crops in a tank mix with a desiccant, application at this earlier stage while pods are still green and supple gives maximum benefit from the product and also moves plants around tramlines, reducing pod shatter from the sprayer when desiccants are applied.

Where crops are even and weed free, natural deciccation will save cost and reduce crop damage from travelling. However this choice requires bravery as harvest timing will be less predictable and very likely delayed. Glyphosate requires patience – it is not a true desiccant, but works by inhibiting amino acid synthesis thus starving the plant. Glyphosate always needs a water conditioner and if difficult weeds are present an adjuvant will better aid their control. Diquat is a true desiccant, working by damaging cell membranes, and therefore needs good coverage and higher water volumes for optimum efficacy. It will be most useful in crops that have more weed pressure or that have lodged.

NOVEMBER
3

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