Fighting back against flea beetle in oilseed rape with drilling date and companion crop16 July 2024
With no magic bullet against cabbage stem flea beetle (CSFB), could adjusting drilling date and planting a companion crop put you in a better position?
That is the thought of ProCam regional technical manager, Nigel Scott, who says we need to think differently about how cabbage stem flea beetle is managed.
CSFB problems can arise whenever winter oilseed rape (WOSR) is planted, he says, but in parts of the country problems seem worse when drilled during its traditional mid to late-August window. This seems to provide a perfect storm for adult beetle invasion and crop failure, he believes.
“If this is the case, depending on individual farm situations, one strategy is to consider planting WOSR much earlier, at the very start of August, or to miss out August completely and plant well into September,” says Mr Scott.
“In both scenarios, varieties need choosing accordingly. Hybrids make sense because you want good establishment from early vigour. But if drilling earlier, you don’t want the crop to get too far ahead over winter, because it will be prone to later frosts.
“Traditionally, varieties have been bred for late-August drilling. So a changed approach means looking at variety choice in a different way – selecting varieties that sit at either end of the spectrum. These might not be on the Recommended List, but have a specific purpose,” he adds.
EARLIER DRILLING
By drilling earlier, Mr Scott says the aim is to get WOSR to 4-5 leaves before adult beetle migration occurs so it can tolerate adult feeding. Larvae are difficult to avoid in this situation, but if a vigorous plant with a thick stem can be created, he says the crop has a fighting chance.
“I’ve seen crops drilled in the first week of August or into July develop a big collar at the base of the plant. This makes them better able to withstand infestation.
“A variety we’ve seen that’s particularly suited to early drilling is LG Areti. It grows away well initially but has a prostrate growth habit close to the soil over winter. So it’s potentially less at risk from frosts while also providing good ground cover.
“Most critical in terms of CSFB is its spring vigour. It’s very quick to move in spring, meaning it can grow away from larval feeding nice and rapidly.”
LATER DRILLING
Alternatively, by planting later, for example well into September depending on location and conditions, Mr Scott says the aim is to plant after adult CSFB migration has finished.
“In September, there should also hopefully be better soil moisture to help establishment and soils should be reasonably warm. However, at this stage, you want a rapidly-establishing plant to compensate for later drilling. You need to grow the most vigorous variety you can.”
Mr Scott’s recommendation here is RGT Blackmoon. “Its vigour in trials has been outstanding, and field performance is equally impressive. I’ve seen Blackmoon drilled in mid-September race away. Drilled alongside an alternative hybrid, it was chalk and cheese, and the vigour was ultimately the difference between survival and failure. Drilling in September is a useful tool for avoiding beetle, but variety choice is essential.”
COMPANION CROPPING
In tandem with drilling date and variety, Mr Scott has had good results with companion cropping to reduce CSFB damage when drilled into stubble.
“A companion crop is a no-brainer for SFI payments anyway. But companion species choice and variety choice are critical if we’re to use them to support our CSFB strategy as well as access the £55/ha payment.
“New for this year, we’re marketing GreenPack Bronze. This companion crop mix contains tartaric buckwheat, which is a ‘must have’ to help shield WOSR from beetles. But it also contains fenugreek, which has a garlic odour to act as a CSFB deterrent.”
Mr Scott says tartaric buckwheat has been selected as a particularly vigorous variety, with a seed size that means GreenPack Bronze can be mixed with the OSR and established together.
“Alternatively it can be established ahead, with the OSR drilled into the protective canopy. Flexibility is key, and the vigour of the companion crop means it is able to provide an IPM tool in either instance as the buckwheat grows ahead of the rape to provide a shield.
“Clearly, companion crops and OSR need moisture irrespective of drilling date, so a stacked approach is needed. Moisture, companions, variety choice and drilling date all need to work together to maximise the chance of success.”
Steps to consider to mitigate CSFB risk
- Plant early or late – to avoid peak adult beetle migration
- Choose a variety that aligns to your planned drilling date – drilling early requires spring vigour, drilling late demands autumn vigour
- Plant a dual-purpose companion crop – providing a shield and deterrent against CSFB
- Plant when adequate soil moisture for rapid OSR and companion crop establishment
LG Areti – breeder’s view
LG Areti is a great variety to drill early due to its growth habit, says Kurtis Scarboro of breeder Limagrain.
“Once it has accumulated good early biomass, it doesn’t get too ahead of itself into autumn, but will begin to race on into spring once day length starts increasing,” he explains.
“Its shorter, stiff straw also adds to its suitability as an early drilling variety, and it’s fully loaded with pod shatter resistance, TUYV resistance and RLM7 stem canker resistance.”
RGT BLACKMOON – breeder’s view
Lee Bennett of RAGT UK, the breeder of RGT Blackmoon, agrees it is well suited to later drilling, for example if drilling later because CSFB is a worry and where powerful, early vigour is required.
“RGT Blackmoon is all about vigour,” he says. “It’s speed of development in autumn is very fast. It sets off and doesn’t look back.
“Agronomically, it’s very good against phoma, good against light leaf spot and is TUYV resistant. It’s also scored well in ADAS work against verticillium. It’s a medium tall type but with very stiff straw, an upright canopy and is medium maturing.”