How to fight back against cabbage stem flea beetle

Adjusting drilling dates and planting companion crops can help combat cabbage stem flea beetle in oilseed rape.

Drilling rape in the traditional mid- to late-August slot can exacerbate flea beetle problems – increasing the chance of crop failure, says ProCam technical manager Nigel Scott. Different thinking is needed to manage the pest, he adds.

“Depending on individual farm situations, one strategy is to consider planting winter rape 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.

“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.”

Earlier drilling

Drilling earlier allows rape to reach 4-5 leaves before adult beetle migration occurs so the plant can tolerate adult feeding. Larvae are still difficult to avoid a vigorous plant with a thick stem will have a bigger chance of survival.

“I’ve seen crops drilled in the first week of August or into July develop a big collar at the base of the plant,” explains Mr Scott. “This makes them better able to withstand infestation.”

One variety 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.This means it is potentially less at risk from frosts while also providing good ground cover.

“Most critical in terms of cabbage stem flea beetle 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

Planting later, such as well into September, means rape will establish after flea beetle migration has finished. But Mr Scott says growers need to consider their individual location and field conditions.

Higher levels of soil moisture in September will also aid establishment But growers should choose a rapidly-establishing variety – such as RGT Blackmoon – to compensate for later drilling.

“You need to grow the most vigorous variety you can,” says Mr Scott. “I’ve seen Blackmoon drilled in mid-September race away. Its vigour in trials has been outstanding, and field performance is equally impressive.

“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 Sustainable Farming Incentive 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 rape from beetles. But it also contains fenugreek, which has a garlic odour to act as a beetle deterrent.”

Tartaric buckwheat was selected because it is a particularly vigorous variety with a seed size that means GreenPack Bronze can be mixed with the oilseed rape and established together.

Alternatively, the cover crop can be planted first, with the rape drilled later into the protective canopy. Either way, the theory is the same: the vigour of the companion crop means the buckwheat grows ahead to provide a shield for the rape.

Clearly, companion crops and rape need moisture irrespective of drilling date, so a stacked approach is needed, explains Mr Scott.

Moisture, companions, variety choice and drilling date all need to work together to maximise the chance of success.”

RGT Blackmoon –breeder’s view

RGT Blackmoon is well suited to later drilling, says Lee Bennett of RAGT UK.

An ideal for growers wanting a powerful variety with early vigour, Mr Bennett says RGT Blackmoon is all about vigour. “It’s speed of development in autumn is very fast. It sets off and doesn’t look back.

“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.”

Four steps to mitigate flea beetle

Make a conscious decision to plant early or late – to avoid peak adult beetle migration

Choose a variety that aligns with your planned drilling date – drilling early requires spring vigour, drilling late demands autumn vigour

Plant a dual-purpose companion crop – to provide a protective canopy to act as a shield and deterrent against flea beetle

Drill when adequate soil moisture will encourage rapid rape establishment and companion crop growth [Source: ProCam]

LG Areti – breeder’s view

LG Areti is a great oilseed rape 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, resistance to turnip yellows virus and RLM7 stem canker resistance.”