The latest Pestwatch report indicates that wheat bulb fly egg-hatch is progressing further in East Anglia, Lincolnshire and Yorkshire and that plant invasion, albeit at low levels, has started in East Anglia and Lincolnshire.
Issued weekly by Dow AgroSciences and ADAS, PestWatch reports help farmers comply with the need to accurately access risk and optimize application timings of the soil insecticide Dursban WG in both winter and spring cereals, so fulfilling an important Stewardship responsibility.
In the last PestWatch report for Wheat Bulb fly for this season, in week-ending the 22nd February 2013, Wheat Bulb fly egg-hatch in Suffolk and in North Lincolnshire on mineral soils were reported to be at 50%, in Cambridgeshire/Hertfordshire on mineral soils it was at 28.6% and in Yorkshire on mineral soils 22.2%.
In Cambridgeshire on organic land, egg-hatch was 52.6%. According to SCUC egg-hatch has started in East Lothian and the Borders of Scotland but is still less than 5%.
There has been some low level plant invasion, but with all larvae still at the first instar stage.
In Cambridgeshire/Hertfordshire and in North Lincolnshire 10% of plants have been invaded and in Suffolk and on organic soils in Cambridgeshire 8%. No plant invasion has been detected in Yorkshire or Scotland.
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.
In Eastern England 47% of monitored sites, in the North 27% of sites and in Scotland 30% of sites were above this threshold level. Many later sown winter crops are potentially thought to be at risk, particularly if they have only one or two tillers at the time of Wheat Bulb fly hatch.
Sarah Hurry of Dow AgroSciences points outs that there are many late drilled, struggling, backward and thin winter crops this year that may well benefit from an application of Dursban WG in order to promote all important tiller survival.
She also warns spring cereal growers to be particularly vigilant to Wheat Bulb fly attack this season.
“Many spring crops are being drilled now at egg-hatch time. Wheat Bulb fly may attack spring barley or spring wheat before crops emerge. Crops at particular risk include those after bare fallow, potatoes, peas and sugar beet."
“In winter cereals, 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.
When applying Dursban WG, growers should be aware of the 14 day interval between applications of Dursban WG and Unite 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 reasons.
"Protecting crop protection products today is even more important than ever. A more stringent 'aquatic organism risk assessment' for plant protection products under routine EU/UK review means that existing label no-spray buffer zones adjacent to watercourses may not be considered sufficient. Adoption of 75% low drift nozzles may allow many crop protection products to pass this aquatic risk assessment."