Pests
Pests
Key Facts
- Aphids, letherjackets and slugs are the main pests of spring barley.
- Late sown crops are more prone to yield loss due to BYDV.
- A fine, firm, seedbed will reduce the risk of damage from both slugs and leatherjackets.
Aphid (BYDV) Management
Aphids are the most serious pests of cereal crops in Ireland. Damage occurs in two ways:
- By transmitting virus disease (BYDV) to and within crops,
- By direct feeding on tillers.
The Grain-Aphid, Sitobion avenae, is the most common aphid vector of BYDV in Ireland. BYDV can reduce the yield of April drilled barley by 2 t/ha, while feeding aphids can reduce yield by 0.8 t/ha. In general, March drilled barley is at lower risk of significant BYDV damage than April drilled barley due to aphid activity patterns (see graph).
Recent research in Ireland has confirmed the development of resistance to pyrethroid insecticides (e.g. cypermethrin) in the Grain-Aphid. Growers need to be aware of this development and consult with their advisors on a suitable integrated pest management strategy.
Aphid Control
- Apply an aphicide at the 3-5 leaf stage (GS13-15) in crops at risk of BYDV.
- All aphicides (incl. pyrethroids) should be applied according to their labels, ensuring good spray coverage.
- Monitor aphid activity after application and where control is poor; consult your advisor and consider applying a non-pyrethroid (e.g. primicarb, chloropyrifos) as a follow-up treatment.
- Do not use pyrethroids to control feeding aphids in cereal ears, use pirimicarb instead.
- Once crops are at milk dough stage (GS75), the yield effect from feeding aphids is negligible.
Leatherjackets
Leatherjackets are the grub of the Crane Fly (Daddy Long-Legs) and are sporadically a pest of spring barley. Where numbers are high (possibly as a result of high autumn rainfall), damage can be significant, especially in slowly emerging crops. Leatherjackets reduce yield by reducing plant and tiller numbers.
Leatherjacket Control
- Monitor cereals (in high risk fields) for leatherjacket damage at early crop emergence. Ensure the seedbed is consolidated with additional rolling will help restrict/kill leatherjacket grubs. Ensure the crop has adequate fertiliser.
- Control is necessary if more than 10 leatherjackets are found in ten 30 cm drill length at 13 cm spacing. Chlorpyrifos (Dursban/Clinch/Trigger) cannot be used from March 31st 2016. The industry is currently looking for alternatives to replace chlorpyrifos.
Slugs
Slugs can also be a problem in slowly emerging crops and reduce yield by reducing tiller numbers. Monitoring numbers by laying traps is the key to their management. Loose seedbeds, previous cropping and field history are important considerations.
Slug Control
- Bait newly sown crops with some muesli or layer mash (not slug pellets due to the risk to wildlife and pets) under a slate. Leave traps overnight and examine early the following morning. If you find > 4 the next morning, consider treatment options.
- Concentrate on fields/areas known to suffer damage.
- If thresholds are breached and the crop is being damaged more than it is growing, consider slug pellet application.
- The common slug control products are based on Metaldehyde and Ferric Phosphate.
- The formulation process of the pellet is important where an extended period of control is required.
Key husbandry factors:
- Early (March) sown crops are less susceptible to yield loss due to BYDV.
- Fine, firm and well consolidated seed beds will reduce the risk of both slug and Leatherjacket damage.