Recognise these beasties? I took these pictures of cabbage stem flea beetle larvae in an OSR crop near Derby, variety Alasco earlier this week.

Drilled early September into good growing conditions, the crop is at about 6 leaves now and mostly under a blanket of snow. The larvae are still hatching and migrating from soil to plant but the recent freezing followed by wet conditions will not help their progress.

On the 10 plants I sampled today, over 3 adjacent fields, the average number of larvae in the leaf petiole is 3.3 per plant, with none having reached as far as the stem or growing point, as of yet. Comparing this to last year, there are slightly fewer per plant and in 2020 approximately 30% of these had made it to the stem or growing point, by this time.

The sold yield on this farm from 2020 was around 2.5t/ha, down on the farm average but still a crop, in a year that threw everything at us. It started with a slow establishment, combined with the highest adult and larvae flea beetle pressure we have ever seen, then followed a wet early spring, a very dry and hot late spring, finishing off with a catchy harvest! Not what I would call ideal growing conditions. As a consequence of these factors, the number growing OSR has dropped, so has that had an effect on the flea beetle pressure?

There may still be a place for OSR as just one of the break crops to consider, with smaller acreages on each farm. An integrated approach to management of the OSR crop will also be essential.

Fingers crossed for this crop, only time will tell…

We’ll be holding an OSR webinar on 4th March to discuss the results from our trials and work to put Agrii’s 8 point plan for cultural control of CSFB into practice. Details will be available shortly on our online events page.