JCSFB damage weakens stem and restricts growth, rendering crops increasingly prone to lodging, ADAS work has confirmed.
ADAS entomologist Fran Pickering says: “It’s long been assumed that CSFB larvae and their activity affect stem strength, but we wanted to know, by how much? And taking it one step further, what impact does that have on lodging?” The ADAS field trials took 50 plants at the end of flowering in May 2020 from two sites in East Anglia.
Strength The team assessed the plants’ stem diameter, breaking strength and the internal damage caused by CSFB.
By assessing the percentage area of stem damaged, the plants were sorted into five categories ranging from ‘minimal’ (plants with less than 5% damage), to ‘severe’ (plants with 76-100% of stem area damaged).
Ms Pickering says: “There was a clear trend showing thicker stems were stronger and while this is not news, the results also showed that higher damage was associated with the thinner stems. But why?”
The CSFB damage was predominantly mining and browning at the base of the stem and this type of damage restricts the take-up of nutrients and water, which in turn, restricts growth, adds Ms Pickering.
“Plants taken from the second site revealed that for any given stem diameter, more damage makes stems weaker.”
The larval feeding not only restricts thickness of the stem but hollows stems, reducing their strength.
“Even low levels of CSFB damage significantly reduce stem strength. On average, stems with less than 25% damage were 29% weaker.”
Agronomic practices adopted to manage CSFB may also contribute to an increased lodging risk.
Berkshire OSR grower Tim Hayward has changed how he grows OSR to combat the effects of CSFB.
He says: “Previously we were drilling after barley. We are a late farm so it would be the first week of September before OSR was in the ground. In 2019 and 2020 we had dry spells in September. That, together with the CSFB damage, meant we had some crop failures.”
“Now, we’re direct drilling into long wheat stubbles and paying much more attention to the forecast.”
Being on thin chalk soils with restricted potential yields, Mr Hayward has not, historically, had a problem with lodging. But moving to conventional seed sown at higher seed rates, combined with some larvae damage, means his crops are higher risk. However, with careful monitoring the risk is manageable, says Ms Pickering.