Newly published research, conducted by ADAS, gives hope for the UK growers to keep oilseed rape (OSR) as a profitable break crop in their rotations.
The four-year study found that it is cabbage stem flea beetle (CSFB) tunnelling damage, rather than larvae number, that is a better indicator of lodging risk in OSR.
Building on ADAS and BASF’s long-term collaborative OSR research, the findings were presented at a recent roundtable discussion.
Dr Thomas Wilkinson, ADAS senior research consultant, shared insight into larval counts and that, even when high, canopy management principles are as important as they have ever been.
“From measuring various stem lodging risk parameters and CSFB damage in over 350 plants, we’ve gained a number of insights that can help growers lower the risk of lodging,” he said.
“Larvae counts have often been used as the primary indicator for CSFB damage, but interestingly, in this study, we noted the percentage of the stem damaged by CSFB tunnelling.”
When OSR has reached its maximum height and is therefore most at risk of lodging, the CSFB larvae will, in most situations, have left the stem, Dr Wilkinson explained.
Even where there are a lot of larvae, the severity of the damage seen compared to the overall structure of the crop can range from high to low, particularly in those plants with thicker stems.
He said: “During the study we used a lodging risk model rather than actual lodging events because it enabled us to take multiple measurements and meant we weren’t relying on the vagaries of the British weather.”
Dr Wilkinson described important new observations in the understanding of CSFB impact from the work.
Researcher found that crops with a high proportion of damage from CSFB larvae were related to reduced stem diameters – which is a key factor in determining stem strength.
Yet the CSFB tunnelling damage they saw, weakened stems more than could be accounted for by the reduced stem diameter alone.
Dr Wilkinson said: “Whether this tunnelling causes thinner stems, or thicker stems dilute CSFB tunnelling damage, we are not wholly sure yet.
“But what we do know is that crops with large robust stems tend to yield well and be more tolerant to CSFB larval pressure.”
He also highlighted the importance of using Caryx, BASF’s plant growth regulator, as it significantly reduced lodging risk by increasing stem strength, in addition to its already understood height reduction.
“Our modelling showed that Caryx reduced the lodging risk from one in three, to one in five or six for a ‘typical plant’," he explained.
