|Wheat Bulb fly larvae munching away at cereal plants|
I expect it is just the farmers amongst you that have ever heard of Wheat Bulb fly, and even then it is only the Eastern based arable farmers who actually have to take much notice of this pest.
Wheat bulb fly is most prevalent in eastern England, the East Midlands and north-eastern England, because the female adult fly likes to lay her eggs in bare soil in July and August, therefore she most often chooses crops that are harvested early, such as vining peas. She also targets the bare soil in between rows of crops such as potatoes, sugar beet and onions and it is in the Eastern parts of the country were most of these crops are grown. These crops are invariably followed by a cereal crop which will be sown in the autumn.
Meanwhile the Wheat Bulb fly’s eggs, which have lain dormant through the winter, start to hatch out between January and March and the little grubs make straight for the cereal plants, attacking the new small shoots that are now a couple of inches or so high. If a farmer has a bad outbreak of this pest, then large yield losses can occur. As a guide, if just 20% of plants are attacked, a potential loss in yield of about 0.7 tonnes per hectare can be expected, which could easily result in the field making a financial loss.
But help is at hand from both the chemical companies and the Home Grown Cereals Authority (HGCA) who continually up-date farmers on the likelihood of there being a problem. Soil samples are taken during the autumn from sites considered to be at risk, to establish the number of Wheat Bulb fly eggs present. From this survey, fields are selected which have high or very high egg numbers present. Weekly soil sampling is then carried out on these selected fields 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.
The HGCA and companies such as Dow then produce constant up-dates for farmers through the period of concern, so that agronomists and growers, who will also walk across their cereal crops to see if there are signs of attack, are helped to make sensible decisions about the need, or otherwise of applying an insecticide.
This is just one example of a process called “Integrated Pest Management” (IPM) which is now practised throughout farming nowadays, resulting in a much better targeted approach to pesticide usage and consequently, only applying a product when absolutely necessary.
The good news is that Wheat Bulb fly seem to be at low levels this year. The latest HGCA Wheat Bulb fly survey indicated that only 7% of sites sampled were above the 250 eggs/m2 treatment threshold, which is the third lowest recorded since 1984.