The latest Pestwatch report indicates that wheat bulb fly egg hatch is well underway in East Anglia, Lincolnshire and has now started in Yorkshire.
Issued weekly by Dow AgroSciences and ADAS, Pestwatch reports on the results of soil sampling at a number of UK sites and aims to help farmers comply with the need to accurately access risk and optimize application timings of the soil insecticide Dursban WG, so fulfilling an important Stewardship responsibility.
For week-ending the 8th February 2013, Wheat Bulb fly egg-hatch had progressed in Suffolk and was reported to be at 20%, in Cambridgeshire/Hertfordshire on mineral soils it was also at 20%, in North Lincolnshire on mineral soils it was 43.8%, in Yorkshire on mineral soils 30.8% and in Cambridgeshire on organic land egg hatch 30.8%.
Progression of egg-hatch will be monitored right into February.
In light of low egg counts in the autumn survey, 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. But the wet autumn lead to many crops being sown much later than planned and many had no seed treatment either.
For such late drilled crops a lower threshold of 100 Wheat Bulb fly eggs/m² will apply. In Eastern England 47% of monitored sites were above this threshold level, in the North 27% of sites were above this level and in Scotland 30% of fields sampled had egg counts exceeding 100 eggs/m². Consequently many later sown crops will still potentially be at risk if they have only one or two tillers at the time of Wheat Bulb fly hatch.
An egg-hatch insecticide spray may be worthwhile, even where egg numbers are only in the moderate infestation category of 100 to 250 eggs/m².
Sarah Hurry of Dow AgroSciences advises growers to conduct risk assessments for specific fields, looking at locality, previous cropping, drilling date, plant population, tillering and soil type. “There are many late drilled, struggling, backward and thin crops this year that may benefit from an application of Dursban WG in order to promote all important tiller survival.”
“Once conditions allow spraying, Dursban WG should be applied at egg-hatch at 1 kg/ha in 200-1000 litres of water. In the event of prolonged egg-hatch, a repeat application of Dursban WG may be required, particularly on organic soils. If necessary Dursban WG can be applied to frosty ground but should not be tank mixed,” reminds Sarah.
Growers are being urged to take precautions to prevent any spray drift by using low drift nozzles and an extended buffer zone when applying Dursban WG. “Protecting 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. An industry Stewardship initiative – Say NO to Drift!- campaign is in place in order to protect the future availability and use of 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.
Trials have demonstrated that control is not affected when Dursban WG is applied using LERAP, low drift 3 star rated nozzles compared with Flat-fan nozzles,” says Dilwyn Harris from Dow AgroSciences.
Dursban WG (75% w/w chlorpyrifos formulated as a Water Dispersible Granule) is recommended for the control of Wheat Bulb fly as well as Leatherjackets, Frit fly and Wheat Blossom Midge. Two applications at dose rates of 1 kg/ha may be applied up until flag leaf sheath extending (GS 39). It is packed in a 1 kg pack.
