Wheat Bulb fly egg hatch progressing rapidly

UK - January 31, 2012

This weeks Dow AgroSciences Pestwatch report shows that egg-hatch is progressing in East Anglia, particularly rapidly in Suffolk.  There has been no change in egg-hatch in Lincolnshire and, as yet, no start to egg-hatch at the Yorkshire site.

Issued weekly by Dow AgroSciences and ADAS, Pestwatch reports on the results of soil sampling at a number of sites across the UK and provide advice on the timely application of the soil insecticide Dursban WG. Weekly information can be accessed at www.dowagro.com/uk/cereal/pest/htm. Week-ending the 26th January 2012, Wheat Bulb fly egg-hatch in Suffolk was reported to be 36.8%, in Cambridgeshire/Hertfordshire on mineral soils was 8.3%, North Lincolnshire (a new site for 2012) on mineral soils 2.3% and in Cambridgeshire on organic land was 10.9%.

Sarah Hurry of Dow AgroSciences explains that results from the HGCA 2011 autumn survey of the incidence of Wheat Bulb fly eggs shows that 20% of crops samples were above threshold.  “For growers in the East, of the 26 sites sampled, 4% were in the very high category of more than 500 eggs/m², 19% were in the high or very high category of greater than 250 eggs/m² and finally 65% were in the moderate, high or very high category of between 100 to 250 eggs/m².”

She reports that of the 15 sites in Northern England 20% were in the high category of ,greater than 250 eggs/m² and 60% in the moderate or high category. “In this part of the country this is similar to last year which was a bad year for this pest and higher than in 2009/10.” In sampling by the Scottish Agricultural Colleges of the 50 fields samples 30% had Wheat Bulb fly populations that exceeded 100 eggs/m², in the low to moderate risk category.

Sarah explains that fields at risk, particularly in East Anglia and Lincolnshire, may need treatment with Dursban WG (chlorpyrifos) at the first opportunity as tiller survival will be important. “In the absence of prolonged cold weather, this application should have activity over the next 5 to 6 weeks on mineral soils. In the event of a prolonged egg-hatch, a repeat application may be required, particularly on organic soils. No start to egg-hatch at the Yorkshire site as yet suggests application timing is not such a priority in this area in the short term.”

She reminds growers that 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 GF-2070 or Broadway Star, regardless of weather conditions. For approved formulations of iodosulfuron-methyl-sodium and mesosulfuron-methyl, a longer interval of 4 weeks is required for crop safety.”

Growers must also make sure that that they take all precautions to prevent drift by using low drift nozzles and an extended buffer zone when applying Dursban WG. The industry Stewardship initiative – Say NO to drift!- has the aim of protecting future availability and use of insecticides containing chlorpyrifos. When spraying Dursban WG for Wheat Bulb fly, growers must use a LERAP rated 3 star nozzle and adopt a 20 metre buffer zone near to watercourses or a 1 metre near to dry ditches.

For further information of Say NO to drift, please go to the web site at www.saynotodrift.co.uk where all the details are explained. On this site there is also a video to show showing spraying with low drift nozzles versus conventional flat-fan applications.

For further information, please contact Sarah Hurry, Dow AgroSciences on the Dow Technical Hotline on 0800 689 8899.