Cereal Pestwatch

Dow AgroSciences UK regularly undertake sampling and monitoring for the most important insect pests of cereals in the UK. 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 weekly during the key periods of potential threat from the relevant pest.

Insect Pest	Initial Sampling	Pestwatch Reports
Wheat Bulb fly	December	January/February/March
Leatherjackets	December/January	March
Wheat Blossom midge	April	May/June
Frit fly	August	August/September

To find out more about this service, please contact our Technical Hotline on 0800 689 8899 or E-mail.

For the most recent Wheat Blossom Midge, Leatherjacket and Wheat Bulb Fly  Pestwatch Reports see below:

WHEAT BULB FLY

Report 8
Date of issue:- 06/03/09

There has been a further increase in the % hatch in the east and in the north this week.  Plant invasion in the east has not increased all larvae are still at 1st instar.  If egg hatch sprays haven't been applied to "at risk fields", an application needs to be made urgently, as soon as field conditions permit.

Site	Viable Eggs	% Hatch	% Plant Invasion
Cambridgeshire
Manea (organic)	6	83.3	0.6
Gt Chesterford (mineral)	6	66.7	-
Linton (mineral)	9	88.9	-
Holme Fen (organic)	15	66.7	1.2
E Yorkshire
Fridaythorpe (mineral)	15	40	0

Action: Use  Risk Assessment Charts  to identify fields at high risk. These are late drilled, e.g. following sugar beet, or backward crops with few tillers and poor overall establishment.  Be prepared to apply Dursban* WG  at 1.0 kg/ha in 200 to 1,000 litres per hectare of water to fields in the highest risk category. Trials conducted by Dow AgroSciences confirm yield increases of at least 0.3 t/ha can be achieved from appropriately timed treatments to control wheat bulb fly.

If necessary, Dursban WG can be applied to frosty ground but should NOT be tank mixed. Dursban WG must NOT be applied in tank mix with Atlantis WG or Broadway* Star, regardless of weather conditions.

An interval of 14 days must be observed between applications of Dursban WG and Broadway Star.

Always read the label. Use pesticides safely.          * Trademark of Dow AgroSciences LLC
Dursban WG contains chlorpyrifos.
Broadway Star contains florasulam and pyroxsulam.

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WHEAT BLOSSOM MIDGE

Report 3
Date of issue:- 08/06/09

Orange Wheat Blossom Midge pupation has advanced and has been recorded at 6 out of 8 sites.  Mean pupation is currently at 7.3% (range 0-14.3%).  Current soil moisture status and temperatures favour further OWBM development in most areas.   There are likely to be hot spots not covered by the survey, so vigilance will be needed everywhere.  Adult male midges have been caught in pheromone traps in a number of locations, with numbers in excess of 100/trap/day in some cases. Counts of females in crops have generally been low, but although some crops in the south are beyond the susceptible stage, some, as you go north, are only at early ear emergence so careful monitoring is still needed.

County	Location	% as pupae
North Yorkshire	Duggleby	12.3
Lincolnshire	Sutton Bridge	7.7
Norfolk	Terrington St Clement	14.3
Cambridgeshire	Boxworth 1	10.5
Cambridgeshire	Boxworth 2	9.2
Suffolk	Haverhill 1	4.5
Suffolk	Haverhill 2	0
Shropshire	Rushberry	0
Mean (8 sites to 29 May 2009)		7.3

 

Any wheat crops at the susceptible growth stage (GS 53-59, ears emerged) must be monitored closely over the next 7 to 10 days. DO NOT apply Dursban* WG  unless ears are emerged and thresholds met or exceeded.

Action: Use Risk Assessment Charts to identify fields at high risk and consider the use of traps at the most susceptible sites. These are typically wheat fields where the pest was noted last year, especially if no treatment was carried out. The economic risk is highest in crops intended for seed or milling. This is reflected in the lower threshold of one midge per 6 ears. The threshold for feed wheat is one midge per 3 ears.

Be prepared to apply Dursban* WG at 0.6 kg/ha in 200 to 1000 litres of water per hectare (leaving an unsprayed headland of at least 12 metres) if thresholds are met or exceeded and crops are at the susceptible GS 53-59 (ears emerged) growth stage.

For further information contact the Dow AgroSciences Hotline - 0800 689 8899

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LEATHERJACKETS

Date Issued:  March 2008

The latest survey from autumn 2007 indicates a much lower risk of damage to susceptible crops in 2008 for England.  In Scotland the high levels of the last four years have also fallen to a little below levels seen in 2002, but 21% of sites were over the cereals damage threshold of 60 leatherjackets per square metre.

ENGLAND
A total of 46 sites were sampled in the three key regions shown below during autumn 2007.  The overall mean leatherjacket population was 15.7/m2 compared with a long term average of 67.6/m2.  The damage threshold for winter and spring cereals is 60/m2.

The Midlands/Western Region comprised Cheshire, Shropshire, Staffordshire, Warwickshire, and Herefordshire where a total of 25 sites were sampled.

The Northern Region covered North, South, and West Yorkshire where 27 sites were sampled.

The Southern Region had six sites sampled covering Berkshire, Hampshire and Oxfordshire.

The survey suggests there is a lower risk of damage to susceptible crops in all regions sampled.  In every case numbers are lower than the long term average.  The substantial reduction in numbers appears to be due to adverse weather in early-mid September. Waterlogging of soils in summer 2007 may also have been a contributory factor.

However, in spite of the low survey numbers, there have been some reports of leatherjacket damage in winter wheat and resown leys.

SCOTLAND
A total of 221 sites in west and central Scotland were sampled during November 2007 - January 2008.  Leatherjacket populations have fallen steeply from the extremely high levels of the past four years.  The overall mean leatherjacket population was 32/m2.  This compares with a 16 year mean of 101/m2. However, 21% of fields sampled had over 60/m2 and in these fields spring cereals will be at risk. Only in Dumfries/Kirkcudbright does the risk appear to be low.

Leatherjacket Damage Thresholds

0.3 million/ha (30/m2)	Population in w & spr. Cereals, sugar beet etc. likely to cause damage
>0.6 million/ha (60/m2)	Autumn grass population likely to cause damage in following cereals
>1 million/ha (100/m2)	Population in permanent grass likely to give economic benefit
>2 million/ha (200/m2)	Population in permanent grass likely to show visible damage

 

ACTION

The risk of economic damage from leatherjackets this season is considerably lower than in recent years for susceptible crops in England and also in Scotland. However, the risk has not gone away. Fields with a history of leatherjacket damage, particularly going into spring cereals, 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.  Because leatherjacket populations will vary from field to field, risks should be assessed before treatment is made. High infestations should be treated as soon as ground conditions permit.  Pre-ploughing treatments 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 per hectare 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.

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Wheat Bulb Fly

Soil samples are taken during December, from sites considered to be at risk, to establish the number of Wheat Bulb fly eggs present. Weekly soil sampling is then carried out during January, February and March to monitor egg hatch and then plant invasion. Monitoring sites normally cover a range of soil types from East Anglia and Yorkshire.

Pestwatch reports are produced to reflect weekly data and provide advice on timely application of Dursban WG. The advice provided also indicates when switching to dead-heart sprays would be most appropriate.

Leatherjackets

Nationwide assessments of Leatherjacket populations are undertaken annually by Dow AgroSciences UK. Soil samples are taken from over 100 representative sites, from the south coast of England, through the south and west Midlands, the north-west of England, Yorkshire and from the west of Scotland.

The results of the surveys are expressed as the number of Leatherjackets per square metre and an indication of the potential for damage to susceptible crops is given. One Pestwatch report is published annually and is normally available in March, to coincide with the drilling of susceptible spring crops.

Wheat Blossom Midge

Soil sampling to establish baseline populations of Wheat Blossom midge is done in April. Representative samples are taken from the key wheat growing areas of England and analysed for the total number of Wheat Blossom midge present. The data also reports the life cycle stage of the midge detected. During baseline sampling most midges are still in the overwintering cocoon stage.

Further soil samples are taken during May and June. The purpose of these samples is to monitor progression through life cycle stages. Suitable weather conditions together with a higher proportion of midge present as pupae in the soil indicate an emergence of adults is imminent. As the situation, and hence potential risk, can change very quickly Pestwatch reports are issued as they are needed throughout May and June.

Frit Fly

Adult Frit fly are trapped, and their numbers monitored, by deploying water traps. The traps are initially set during early August and reset and monitored weekly for around six weeks. This gives an indication of the potential risk to susceptible crops from third generation Frit fly. Traps are normally placed in south-west England, the west Midlands, north-west England and North Yorkshire.

Pestwatch reports are issued weekly during this time, indicating numbers caught, the potential risk and appropriate use of Dursban WG. Where numbers of adults are relatively low, but still sufficient to cause problems in emerging crops, the Pestwatch report will recommend the lower Integrated Pest Management rate of Dursban WG be applied.

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