Report 15th February 2013

In support of the product stewardship of Dursban® WG, Dow AgroSciences in conjunction with ADAS, will be monitoring Wheat Bulb fly egg-hatch and subsequent plant invasion. This helps farmers comply with needs to accurately assess risk and thus optimise product usage.
 
The latest HGCA Wheat Bulb fly survey indicated that only 3% of sites sampled in England were above the threshold of 250 eggs/m2. This was the equal lowest recorded since 1984. The full survey results are available on the HGCA website www.hgca.com. A similar low risk was indicated by surveys in Scotland by SAC Consulting / SRUC.

Late sown crops at risk

In view of these low counts it was predicted that Wheat Bulb fly would pose a limited threat to crops sown before November and many crops did not receive any Wheat bulb fly seed treatment. However the wet autumn delayed drilling and plant development.  Therefore many crops were sown late and for these a lower threshold of 100 eggs/m2 will apply.  In the east of England 47% of monitored sites were above this level and in the north of England 27% of sites were above this level.  In Scotland 30% of fields sampled have egg counts exceeding 100 eggs/m2. As a result later sown crops will still potentially be at risk if they have only one or two tillers at the time of Wheat Bulb fly egg-hatch. In this instance an egg-hatch spray may be worthwhile even if egg numbers are only in the moderate infestation category (100-250 eggs/m2).

Slow developing early drilled crops will also need to be monitored and may benefit from an egg-hatch spray if they have low numbers of tillers and egg numbers are in the moderate infestation category.

Progression of egg-hatch will be monitored into February.

Results

Egg hatch is progressing quite rapidly in the east with Suffolk and Cambridgeshire sites at or above 50% hatch and North Lincolnshire at about 44% hatch. Plant invasion is apparent at these sites but at a low level, and has in fact decreased from last week, possibly as a result of the weather. Results from Steeple Morden represent somewhat of an anomaly and are most likely the result of the low egg numbers recovered from this site.

Egg hatch remains at the early stages in the north and as such, no plant invasion has yet been observed. According to SRUC, the start of egg hatch in Scotland is anticipated in the next few days. All larvae remain at first instar.

In the absence of egg counts for specific fields, risk assessments for treatment must be made on the basis of locality, previous cropping, drilling date, plant population, tillering and soil type. Use Risk Assessment Charts to identify fields at risk. Once conditions allow apply Dursban WG at 1.0 kg/ha in 200 to 1000 litres per hectare of water. In late drilled, struggling, backward or thin crops an application of Dursban WG should be considered at the first available opportunity to promote tiller survival. In the event of a prolonged egg-hatch a repeat application of Dursban WG may be required, particularly on organic soils.

Spring cereal growers should be particularly vigilant to Wheat Bulb fly attack this season. Should egg hatch coincide with drilling spring wheat and barley crops, or even late drilled winter cereals, growers should monitor crops closely.

If necessary, Dursban WG can be applied to frosty ground but should NOT be tank mixed.

An interval of 14 days must be observed between applications of Dursban WG and UNITE® or Broadway® Star, regardless of weather conditions. For approved formulations of iodosulfuron-methyl-sodium and mesosulfuron-methyl leave a longer interval of at least 4 weeks for crop safety.

Equity® also has recommendations for Wheat Bulb fly.

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

Protecting the crop protection products we have available today is more important than ever. A new ‘risk assessment’ for chlorpyrifos, under its routine EU/UK review, means that the existing label no-spray buffer zones adjacent to watercourses are no longer considered sufficient protection for aquatic organisms by the Chemicals Regulations Directorate (CRD). An industry stewardship initiative – ‘Say NO to Drift’ is in place.   The aim of this campaign is to protect the future availability and use of chlorpyrifos.  

When spraying Dursban WG or Equity for Wheat Bulb fly:
•    Use LERAP - low drift - 3 star rated nozzles
•    Adopt a 20 metre buffer zone (1 metre dry ditch)
Trials conducted by Dow AgroSciences have shown that control of Wheat Bulb fly is not affected when Dursban WG is applied using a LERAP  - low drift - 3 star rated nozzle (compared to a Flat-fan nozzle).