An industry led campaign launched to reverse the decline in the UK’s oilseed rape area has put together a set of cabbage stem flea beetle (CSFB) management tips to help growers cope with the pest.

While some of the advice from the OSR Reboot initiative is well-known and widely adopted, some tips are there to help growers tap into new research as it emerges.

This is according to Dr Sacha White, lead crop protection scientist at the AHDB, who is one of the key members of the group.

See also: Lower flea beetle numbers found in nationwide monitoring project

The project’s 10 top tips

1. Ditch the date

Probably the most widely publicised advice for mitigating adult flea beetle damage is to avoid sowing the crop around peak migration of the pest when it is most active.

This tends to be the end of August to the start of September.

Sacha says: “When looking at sowing date, think about going early or late. Early means early to mid-August to maximise the crop’s ability to cope with adult feeding.”

However, any crops drilled before mid-August tend to have a higher larval load later in the autumn or following spring.

“It is useful to treat adult beetles and larvae as two separate problems in this respect. Sowing date is really important here, because it helps inform you of the sorts of problems you’re likely to encounter.”

The alternative is to wait until mid-September, so crops will emerge after peak pest migration has passed.

CSFB tend to be elsewhere in other fields by the time these crops emerge so there is less adult damage and much less larval load.

Whatever date growers choose, moisture should always be king.

“If there isn’t moisture there, you are going to establish a poor crop that will be perfect for flea beetle to pick off as it emerges.”

2. Fine tune crop establishment

It is critical to get the crop established well, and in the best conditions.

“One of the most important things with OSR is attention to detail,” says Sacha. “Gone are the days of OSR being an easy crop that you can just throw in the ground and not worry about.”

This means a decent seedbed, with good seed to soil contact and appropriate moisture.

“Choose a variety that suits your sow date, so if you’ve got a mid-late drilled crop, ensure it has good autumn vigour so it will get up and away quickly, and have more leaf material by the time flea beetle arrive.

“Use good quality seed and consider adding nutrition to get the crop away. If you are using farm saved seed, screen it to make sure you are using larger seed that is 1.8-2.2mm in size,” says Sacha.

Strategies such as leaving the previous year’s stubble can make it harder for flea beetle to find the crop.

It is also important to consider the season, for example a wet autumn will likely need good slug control measures, he adds.

3. Isolate your crop

Although not necessarily possible on all farms, growing OSR crops as far away from previous or other OSR can help reduce pest burden.

“Flea beetle can fly at least 2km so if yours is the only crop in the area, you could get a lot of damage,” says Sacha.

4. Build larval tolerance

There is a growing body of evidence to show crops drilled at lower seed rates lead to more vigorous, bushier and bigger plants, which are more tolerable of larval feeding.

Similarly, varieties with good spring vigour that put on growth early towards the end of winter and early spring.

5. Apply organic amendments

Applications of organic amendments at sowing or during establishment can aid crops.

“Whether that’s manure or chicken muck, we see better establishment and lower damage in crops. The reason is based on theories, but it is likely because it’s getting crops growing quickly.

It could also be the flea beetle are actively deterred by the smell, or the smell is masking the crop, so it’s harder to find.”

6. Avoid pyrethroids in England

Pyrethroid resistance in CSFB is found throughout England, with growers unlikely to get much control, if any, from the insecticide.

“However, you will knock back natural enemies like parasitic wasps or ground beetles, which are more sensitive to pyrethroids than the pest now, essentially making things worse,” warns Sacha.

Pyrethroid resistance is rarer in Wales, Scotland and Northern Ireland, so growers can generally still get control from the insecticide.

However, these should only be used as a last resort and when treatment thresholds are reached, to reduce resistance risk.

7. Sow companion plants

Planting a companion crop a week or so ahead of OSR can lead to reductions in adult feeding damage by about 40%.

Plants that are frost sensitive or easy to manage with a herbicide such as berseem clover, buckwheat and fenugreek are beneficial. Intercropping with faba beans provides similar benefits.

“As part of an IPM programme, companion crops can be a key component.”

It is not yet known why companion crops help to deter flea beetle.

Sacha says it could be down to multiple factors including their soil conditioning properties, the fact they are masking the crop from the pest, or because they are providing habitats for natural enemies to thrive.

8. Leave trap crops

Waiting until late September to destroy volunteers in fields coming out of OSR can be effective in luring CSFB away from emerging crops.

Alternatively, growers could try sowing borders or strips of turnip rape, to draw CSFB away.

Sacha says: “If you can’t isolate a crop, leaving volunteers is a good way of creating a trap crop.”

It is also possible brassica-rich cover crops have been acting as trap crops, which could be part of the reason there was lower flea beetle pressure last autumn.

9. Cultivating stubbles soon after harvest

When CSFB typically re-emerge in June, it snacks on OSR but cause little damage, before entering a period of summer hibernation in sheltered areas such as hedgerows, field margins or burrowing into soil.

Cultivating the crop immediately after harvest can kill off dormant CSFB in the soil, preventing it from moving into new crops.

Sacha emphasises more work needs to be done to determine the impact this could have on dormant beneficials such as parasitic wasp pupae.

10. Hidden gems

As well as cultural options, there are “hidden gems” that can be included to provide incremental control.

“Seed treatments like Lumiposa provides some control of CSFB, and there is anecdotal evidence to suggest applying silica products can reduce adult damage.

“Anything you can do to promote natural enemy activity will help.

“If you have a high larval load, you could consider grazing or topping. There is a lot of work showing this helps, but it has to be done right.

“Don’t do it any later than December, and not too severely so not to reduce yield.”