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Pests in Spring barley, April 2019

4 April 2019

Crops sown after grass will be at risk from leatherjackets. With the loss of chlorpyrifos, crops sown after grass have limited options should leatherjackets start to cause damage to emerging crops. One option is extra cultivations, as ploughing reduces populations by about 50%. Rolling the seedbed with a heavy roller immediately after sowing can also reduce damage by leatherjackets.

Slugs may be an issue this season as they have enjoyed the recent wet conditions. Check for signs of leaf shredding at early crop emergence. Bear in mind that if you are to use slug pellets that there are guidelines as to how much metaldehyde pellets you can apply, and that no metaldehyde pellets should be allowed to fall within a minimum of 10 metres of any field boundary or watercourse. A maximum of 700g metaldehyde a.i. is allowed in a calendar year, with a maximum of 210g after August. Ferric phosphate products are good alternatives to metaldehyde.
Other pests such as rabbits and wireworm can all have an impact on crop establishment. Make sure that the cause of any poor growth is determined as options for control of the above will vary.

There is also the threat from barley yellow dwarf virus (BYDV) being transmitted by aphids walking onto the spring barley crops via the ‘green bridge’. Aphids pose a threat by walking onto germinating crops from stubble, grass and volunteers. The winter and current wet cold weather may well have knocked back aphids on stubble and volunteers, but crops should be monitored from emergence for the presence of aphids. Aphids are expected to fly into crops in mid-late April this season so crops could well be at risk from BYDV this season. A pyrethroid aphicide is the only option but we need to avoid unnecessary applications due to resistance in the grain aphid, so monitor crops at emergence and only use an aphicide if necessary.

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