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ADAS research shows PGR reduces lodging risk caused by CSFB larvae damage

ADAS researchers have discovered that using Caryx can o set the increased lodging risk caused by cabbage stem ea beetle (CSFB) larvae damage inside the stem.

In replicated trials in North Yorkshire and Norfolk last year, the pest’s activity increased lodging risk from 33% to 60% but the use of Caryx reduced that risk below the baseline to 20%.

“CSFB larvae reduce stem strength and stem diameter. They may also reduce height slightly, but not enough to compensate for the decreased stem strength. CSFB larvae damage lowers overall wind resistance, and the crop is more likely to lodge,” explains Pete Berry (left), ADAS head of crop physiology.

“Caryx reduces plant height and consequently, has a positive e ect on increasing wind resistance,” he comments.

Mr Berry has typically seen Caryx reduce OSR plant height by 10cm in trials. “That will reduce lodging risk substantially,” he says. “We’ve also seen reductions of up to 20cm. How much you get, depends on the growing conditions at time of application but Caryx is probably the most e ective PGR for reducing height.”

Reduced nitrogen impact

Further research looked at the the relative impacts of reduced nitrogen applications. Conducted in spring 2022, the trial compared the e ects of the PGR alongside a standard nitrogen regime and a reduced programme.

“The crop was forward and had high CSFB larvae pressure of 14 larvae/plant in the March. Otherwise, it exhibited normal development,” recalls Mr Berry.

The standard nitrogen regime (in accordance with RB209 guidelines) saw a total of 140kg N/ ha applied to the crop. An initial 40kg N/ha was applied at the end of February, 60kg N/ha at green bud and 40kg N/ha at yellow bud. The experimental reduced nitrogen regime omitted the rst dose.

“Under both nitrogen regimes, Caryx signi cantly increased wind resistance and therefore reduced lodging risk,” explains Mr Berry.

“Despite previously nding reducing nitrogen can lower lodging risk, in this trial it did not. This may have been caused by the dry March and April, which could have a ected uptake. Yield was reduced as expected.”

Managing lodging risk this spring

For growers looking at managing crops this spring, Mr Berry says delaying the rst split can be useful for those crops with a large canopy (a GAI of 2 or more) in February. A more drastic option is to reduce the overall rate of nitrogen, but this may also reduce yield and can only really be justi ed where the lodging risk is very high and/ or fertiliser prices make it a more viable option.

“Ultimately, the most consistent and e ective way to reduce lodging risk comes from using a PGR such as Caryx,” he comments.

This latest advice comes in a season where growers are potentially facing a higher than usual risk of lodging as a result of good establishment, a mild winter and moderate CSFB pressure last autumn.

“Generally, growers held out for moisture, and OSR was drilled into decent conditions,” notes BASF agronomy manager, Matt Keane (left). “It has been a mild winter so far and OSR crops are looking as good as perhaps they ever have.” far and OSR crops are looking as good as the

According to Mr Keane, any crops with a GAI above 0.8 at the end of February, just before stem extension, warrants an application of Caryx. “Usually, we recommend application rates of 0.7-litres/ha to 1-litres/ha, but where crops are very large, you can go up to 1.4-litres/ha,” he says.

Optimum timing of applications is green bud to yellow bud when crops are actively growing. Mr Keane advises growers to aim for green bud rather than yellow when facing a larger canopy. “Also look at the nutrient status of that crop. Where the land is very fertile, consider upping the rate of Caryx.”

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