Following the proposal to ban neonicotinoids, what is the alternative solution? The answer is simple but needs thinking about well in time for planting in August. Firstly you must choose a vigorous variety. And secondly you must give it the best chance to grow away and establish by working the seedbed well,” says Neil Groom, technical director for Grainseed.
Neil says that growers should not make the mistake of over-simplifying this choice because autumn vigour is a characteristic of the individual variety, not the variety type. “In other words not all hybrids are vigorous whilst some conventionals are very vigorous. It is a message that we have been sending out to the market place for a few years now. But this coming autumn without neonicotinoids to fall back on, it has never been as crucial.”
This view is also held by variety specialist Simon Kightley of NIABTAG who has measured vigour using three specific criteria – young plant height, number of leaves and ground cover in a multi-site three-year experiment. He is quoted “These measurements show that vigour is something that varies tremendously from variety to variety and that some conventional rape varieties are just as, and in some cases more vigorous, than hybrid varieties. Results illustrate that you have to look at the individual variety itself, not just whether it is a conventional or a hybrid.”
Doug Balderson, director of independent merchant and distributor Doug Balderson Agriculture Ltd, says that the conventional winter rape variety Mambo has excellent autumn vigour with strong standing power and lodging resistance. “Mambo grows away strongly in the autumn giving growers the best chance of the crop outgrowing cabbage stem flea beetle, slugs and Phoma stem canker,” comments Doug.
Neil Groom suggests that adopting the practise of early season nutrients could also boost growth early on and should also be adopted. “Following wheat, there is likely to be little residual Nitrogen in the soil as the crop will have taken it up or it would have leached from the soil. Applying 40 kg/ha of Nitrogen for rape establishment should become the norm in my view. But I would advise that nutrients are applied in the seedbed, rather than once the crop has emerged, as the Nitrogen needs to be fully available in soil solution as soon as the plant has used up its seed reserves. Applying to the emerged plant is too late.”
Mambo has one of the highest disease resistance ratings to Phoma, “Varietal resistance in rape is an underrated benefit. Mambo has a Phoma resistance rating of 7.8, a sound rating for Light leaf spot of 6.4 and is also resistant toVerticilliumthat is much more widely found nowadays. Planting a tolerant variety is an important way to minimise Verticilliumas we have no approved chemicals to control this soil-borne disease. For Phoma it gives you more thinking time and you could be able to save on an autumn fungicide,” Neil says.
Mambo also has good standing power (a rating of 9 for resistance to lodging and an 8 for stem stiffness) and its low biomass helps with combining by reducing the volume of material to cut. Such a variety will save on combining costs and time. Mambo is a conventional low biomass winter rape variety. “It has exceptional autumn vigour which, without the availability of neonicotinoid seed treatments any more, is essential. This vigour helps the crop grow away from damaging flea beetle attack and reduce the levels of Phoma cankers too.”
Finally Neil says that the cultivations must be up to scratch. With autocast and direct drilling, rolling is important to crack straw over and stop any moisture loss through the wheat stubble. Firming the soil will also reduce slug movement under the straw mat. With the restrictions on neonicotinoids now, rapid establishment, Nitrogen in the seedbed and early autumn vigour are fundamental to securing your rape crop over the problematic autumn/winter period.”