East: Neonic seed treatments help reduce flea beetle pressure

After a somewhat protracted harvest, most in this area are now finished, with good yields and quality achieved. Unfortunately whilst updating budgets with estimated yields and price the net result is comparable, with lower prices negating the higher yields. The encouraging thing is that where yields have significantly exceeded the budget we will hopefully still come out on budget, proving that yield is still king and one area we can still influence, even if it was the increased radiation that contributed most.

The oilseed rape area has reduced significantly on the back of the cabbage stem flea beetle issues of last year, replacing the rape area with barley, oats or beans. Where OSR is still being grown, many have managed to use neonicotinoid-treated seed, which has helped reduce the early pest pressure and with regular rain the crop has kept growing away.

The aim was to plant in the second and third week of August to get two leaves on the crop by the end of August, which in most cases has been achieved. Some of the later planted crops have struggled a little with slow growth during the cold nights, but with the regular rain crops are generally growing away from damage. Cabbage stem flea beetle samples were sent to Rothamsted Research post-harvest for resistance testing, with the results suggesting an average of 25% pyrethroid resistance. Subsequently, where appropriate, pyrethroids have been used to control adults found in crops and appear to have been effective.

The earlier drilling has resulted in other problems in terms of blackgrass emergence and where the crop is at least 2-3 leaves and the blackgrass at 3-leaf we are applying Centurion Max (clethodim), plus X-change water conditioner in hard water areas. With the timing restrictions around the product and the no other treatment 14 days either side of application, it is essential to ensure the crop is growing away from any flea beetle damage prior to application.

Although crops are growing away well they should be monitored throughout September and October. Surviving adults will begin laying eggs at the base of the plant in early October onwards and it was the subsequent larvae that hatched and burrowed into leaf petioles that caused massive damage last year, so we are not yet out of the woods.

Adas have reported ‘moderate’ blackgrass dormancy and it is growing quite happily in stubbles and stale seed-beds. Make the most of the opportunity to achieve several stale seedbeds prior to cereal drilling. This should involve spraying off the seed-bed and crucially lightly moving the ground to encourage a further flush. Do not be rushed into drilling before you are happy you have had a suitable flush of blackgrass for what you would expect from a particular field. The order of drilling should also be based on blackgrass risk, with the low risk fields drilled first to allow further weed flushes on the worst fields.

This year is very different to last year, when we had little blackgrass germinating until October. We have had moisture and blackgrass germinating for a month already, so drilling date should be driven by how successful blackgrass germination and stale seed-beds have been in relation to the level of blackgrass you are expecting.

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