VIGOROUS FAST-DEVELOPING DEKALB VARIETIES MINIMISE ESTABLISHMENT RISKS
- OSR hybrids that are faster to develop before winter and start stem elongation earlier in spring can markedly limit damage from cabbage stem flea beetle larvae.
- Rapid development before winter and early stem elongation in spring are also valuable in providing the greatest possible tolerance to slug and pigeon problems.
- Furthermore, better grown crops coming out of the winter offer the opportunity to save around £20/ha on spring canopy nitrogen.
Winter OSR establishment and survival into the spring can be seriously compromised by a number of pests – most notably cabbage stem flea beetle, slugs and pigeons.
Heavy autumn flea beetle and slug grazing can completely destroy emerging crops, while less severe infestations result in very uneven establishment and large areas of plant loss that markedly reduce productivity.
Early flea beetle attack is invariably more damaging where soil moisture limitations restrict the speed of crop establishment, while slug damage is worse where autumn conditions are wetter.
Beyond the initial leaf damage caused by the adults, flea beetle larvae feeding within the stem can then lead to major losses of stems and badly stunted plants which are also much more susceptible to frost damage over the winter.
Slugs can cause problems for an extended period in relatively mild winters. In contrast, where cold winter conditions limit the availability of alternative foodspigeon grazing can rapidly defoliate crops in some areas.
In the absence of neonicotinoid seed dressings, pyrethroid sprays offer the only chemical defnce against flea beetles. The growing incidence of pyrethroid resistance across Europe is, however, progressively limiting their effectiveness.
Slugs can be effectively controlled using specialist surface baits. However, they need to be applied regularly to maintain their activity in wet weather, in particular, and are subject to increasing restrictions on their use.
While they are unlikely to be able to resist the heaviest infestations, we have found the vigorous establishment we have always prioritised in our improvement programme allows varieties to tolerate attacks that can be extremely harmful to those with less establishment vigour. We also see rapid autumn development as a valuable pest management characteristic in enabling varieties to more reliably grow away from early flea beetle and slug attack.
Where pigeons are a problem, it can be very useful too. This is primarily because birds actively avoid landing in crops with the most complete canopies to ensure they keep themselves dry enough for rapid take-off in the event of danger.
The latest studies have shown that our varieties which develop more rapidly before winter and are earlier to commence stem elongation in the spring can limit the damage caused by cabbage stem flea beetle larvae.
Under very high infestation conditions these varieties lost noticeably fewer of their main stems and showed far less stunting than varieties with a slower early speed of development or a less early start to stem elongation.
They were as infested with larvae as less rapid early developers but, assisted by a greater branching ability, their extra biomass and earlier spring regrowth enabled them to cope better with the damage caused.
As an alternative strategy, our less rapidly developing varieties are best suited to regimes in which the crop is sown as early as possible in August to get it through its most vulnerable stage before the peak of cabbage stem flea beetle emergence.
Regardless of their speed of early development, of course, vigorous varieties with the ability to grow away early in the spring offer the greatest possible tolerance to winter slug and pigeon attack.
DK EXALTE A leading combination of fast early plant development and DEKALB’s yield protecting traits. Learn More
DK EXCLAIM A stiff stemmed high yielding variety with DEKALB’s leading yield protecting traits. Learn More
DK IMPERIAL CL The Benchmark Clearfield Variety. Learn More
DK EXPEDIENT New from DEKALB, rapid developing, early to harvest, high yielding variety. Learn More