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Alternative strategies for CFSB control needed this spring

10 May 2016

Controlling cabbage stem flea beetle (CSFB) is going to need a step change in approach, was the warning from Alan Dewar of Dewar Crop Protection, at the recent Association of Independent Crop Consultants annual Conference (AICC), near Towcester, Northamptonshire.

Where crops are badly infected we could be looking at infection levels of over 2 million adults/hectare and programmed spraying will not control this, which leaves us in a crisis situation, with regards to effective control of CSFB, he said.

“Flea beetles move about at different times every autumn so it’s difficult to get the timing right for spraying. Also we cannot ignore the fact that there is increasing resistance to pyrethroids; we are looking at over 50% resistance in some areas, and I don’t see any effective control from other non-pyrethroid autumn sprays such as Biscaya, which leaves us without a viable control option.”

So what can be done to help control this devastating pest in oilseed rape?   He asks.

“We need to look at cultural control practices such as early sowing; August if possible. Increasing seed rates will also help to dilute the damage a given population of beetles will have.”

He also suggests removing flushes of volunteers thereby depleting the food source of the adults that are developing their ovaries in an attempt to reduce fertility before they attack the newly emerged crop.

“Consider providing a trap crop around the edge of the main crop as this may encourage the beetles to lay their eggs in the trap crop and not the main crop, and this can be sprayed off in late autumn to take them out.”

Longer term Dr Dewar believes that an inability to control CFSB could move OSR production to areas where currently the threat is reduced such as the north and west. 

 “Although a bit extreme, in some areas we may even need to consider putting sheep into established crops to eat the leaves containing the flea beetle larvae. This might reduce the number of larvae pupating in the soil, and thus reduce adult emergence in the summer.”

“What is certainly needed is a comprehensive, independent study to devise an IPM strategy for controlling this now-epidemic pest, as we can longer rely on established control methods.”

Recent figures published by the AHDB estimate that 1%, which is about 6,000ha, of winter oilseed rape crop losses will be due to cabbage stem flea beetle activity.

As in 2014, crop loss and damage estimates were calculated by ADAS using information supplied by AICC agronomists.

For more information go to:

http://cereals.ahdb.org.uk/publications/2016/january/27/cabbage-stem-flea-beetle-live-incidence-and-severity-monitoring-2015.aspx

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