How can we manage the Cabbage Stem Seed Beetle risk?

Key considerations:

Loss of Insecticidal seed treatments

Insecticide resistance

Pre-drilling considerations

Drilling time – forget about the calendar

 

Cabbage Stem Flea beetle.jpg

With the loss of neonicotinoid seed treatments and resistance to pyrethoid chemistry, we have seen crop losses of up to 11%, a figure steadily increasing over the last 5 years.

Without these tools we are having to turn more seriously to a more integrated Crop approach to maintain OSR as our main break crop.

What are the key factors we need to consider?

Before drilling

Leave long straw stubbles in fields planned for OSR crops, this disguises the field as being brown in colour, especially when the crop is green & vulnerable at the early cotyledon stage.

Don’t destroy volunteer OSR plants in neighbouring fields too early, these can significantly reduce the numbers of adults affecting the newly sown crop next door. This effectively breaks the life cycle of the pest. More research is being carried out to investigate this method of field trapping.

 

Drilling Time

We have seen no significant difference between varieties, but we do need to consider vigour of the variety both in the autumn but just as important in the spring.

Does drilling date make a difference? We have seen from this current season that the early drilled crops have suffered most from the increased larval burden, causing loss of plants both in the autumn but more shockingly in the spring as late as March and April. This is compared to later drillings which have suffered more from adult damage. Most of the migrations start at the end of August.

 

Establishment

This needs to be key over gross output at the present time. The drilling window is anytime between early August and mid-September. Always drill into moisture and forget about calendar dates. Consolidate seedbeds to conserve moisture, with the additional benefit of restricting beetle movement. We suggest two passes of the rolls at 900  if possible.

Our DAP + polysulphate blends are ideal as a seedbed fertilizer, with the sulphur increasing glucosinolates, which act as a natural plant defence mechanism against pests.  Root enhancing seed treatments as well as a well-timed zinc or phosphite based materials will also encourage early root growth.  Later drilling in early September will reduce the larval burden, while egg hatch will be later and slower due to cooler temperatures.

Do we spray with a pyrethoid?

If we reach out for the spray can, are we just comfort spraying? In many cases we are doing more harm than good by killing off Beneficial’s such as ground beetles, which have an appetite for the eggs. A new registration has now been approved for autumn use of Tau -fluvalinate (Mavrik) which is claimed to have less effect on these beneficial.

Companion Cropping

Much work is going on regarding companion cropping, ranging from buckwheat to mustards. We don’t want the companion crop to compete with the main OSR crop, and we need to decide on when these companion crops need to be destroyed. If using a Clearfield variety, other brassica crops can be easily removed with the Clearfield chemistry, but other crops may have to rely on first frost. More work needs to be done in this area as there are still many unknowns.

Seed dressings

Currently there are no UK registrations for the Corteva active, cyantraniliprole (OSR seed dressing), which has been available in other EU states since 2017. Seed can be purchased from imported sources legally, but cannot be supported by Corteva until UK registration is received in the future.

Summary

OSR is still one of our best break crops.

Establishment is key.

Make use of as many cultural methods before grabbing the chemical can.

More research on many other cultural methods of control are currently being worked on.