Sugar Beet Pestwatch

    

Dow AgroSciences UK regularly undertake sampling and monitoring of Leatherjacket populations throughout England and Scotland. The studies are carried out in conjunction with ADAS in England and SAC in Scotland. Pestwatch bulletins are prepared from the results and normally issued in March to alert sugar beet growers to the potential for damage from Leatherjackets to the newly-drilled crop.

The most recent Pestwatch Report:

March 2012

Each autumn Dow AgroSciences commission ADAS and the SAC to survey leatherjacket numbers across England and Scotland as part of its commitment to the stewardship and product support for users of Dursban* WG and Equity*.

All sites sampled were in grassland. Results give an indication to the risk to susceptible crops including spring barley and sugar beet.

Scotland

A total of 219 fields were sampled in west and central Scotland.

Leatherjacket numbers are generally similar to last year, although the proportion of fields containing more than 1.0 million leatherjackets/ha has fallen from over one-third of the fields sampled last year to less than one-quarter of the fields sampled this year.

The highest field population recorded was 9.3 million leatherjackets/ha in Bute.

In general in Scotland, the risk of damage to fields remaining as permanent grassland is low. However, one-third of fields sampled contained populations in excess of 0.6 million/ha, and hence there is some risk of damage to following crops of spring cereals after grassland. The risk is highest in Argyll, Bute, Renfrewshire/Dunbartonshire and Wigtownshire; relatively high in Ayrshire and Stirling/Perthshire; and generally low in Dumfriesshire/ Kirkudbrightshire and Lanarkshire.

England

A total of 46 grassland sites in England were assessed for the presence of leatherjackets.

In England there are low populations of leatherjackets. The only exception to this is West Yorkshire where mean numbers increased by 174% in comparison to last year and 50% of sites were above 0.5 million leatherjackets/ha. Overall 6 out of 46 sites (13%) had leatherjacket numbers at or above 0.5 million leatherjackets/ha – a level likely to cause damage in following crops of spring cereals.

Mean leatherjacket populations by region in 2011/12 were 0.11 million/ha in Cheshire, Shropshire, Staffordshire and Herefordshire, 0.37 million/ha in Yorkshire and 0.1 million/ha on Berkshire, Hampshire and Oxfordshire.  Compared with 2010/11, mean numbers of leatherjackets increased in all areas.  Despite these increases the population is still low and significantly below the numbers recorded between 2004 and 2006.

The highest population for an individual field was 0.6 million/ha, which was recorded at Shocklach in Cheshire.

Leatherjacket Damage Thresholds

 >0.25 million/ha  (25/m2)  Damage likely in sugar beet and other row crops
>0.5-0.6 million/ha  (50-60/m2)  Autumn grass population likely to cause damage in following cereals
>1 million/ha (100/m2)  Population in permanent grass where treatment likely to give economic benefit
 >2 million/ha (200/m2) Population in permanent grass likely to show visible damage if untreated

 

Action

In both England and Scotland the risk of damage is low for grassland. However, for spring cereals following grass the risk has not gone away and special attention should be given to crops in West Yorkshire, Argyll, Bute, Renfrewshire/Dunbartonshire and Wigtownshire.

Elsewhere fields with a history of leatherjacket damage should be monitored for large numbers of rooks and crows feeding on the larvae. Risk assessments and testing for the presence of leatherjacket larvae will provide a good indication of fields that are most likely to need treatment.

Pre-ploughing treatments on grassland are more effective than those applied once damage is underway in the new crop.

If treatment is justified use Dursban WG  at 1.0 Kg/ha applied in 200 to 1000 litres of water.

If using Equity the recommended rate is 1.5L/ha applied in 200 to 1000 litres of water.

Control will be reduced if temperatures are below 5oC as the larvae will move deeper into the soil profile.

Use low drift nozzles and extend buffer zones to preserve Dursban WG use!

When spraying Dursban WG or Equity for leatherjackets with a conventional boom sprayer:
• Use LERAP – low drift – three star nozzles
• AND adopt a 20 metre no-spray buffer zone (1 metre for dry water bodies)

 
Use plant protection products safely. Always read the label and product information before use.
For further information including warning phrases and symbols refer to label.

Dursban and Equity are trademarks of Dow AgroSciences LLC. All other brand names are trademarks of other manufacturers for which proprietary rights may exist.

Dursban WG contains chlorpyrifos
Equity contains chlorpyrifos