After two hot summers, a picnic in the countryside has turned into a battle with nature - but only for the picnicker who selects the wrong spot. Localised 'pockets' of the plague, where insects are resistant to chemicals, have been reported throughout the country.
Householders in these areas have complained in record numbers to pest control officers and local councils. For thousands of country dwellers, old-fashioned fly-papers - changed frequently - are the only alternative to sharing the house with buzzing insects.
The culprits are Musca Domestica, the common house-fly, and Fannia Canicularis, the lesser house-fly. Both species like to share their lives with humans in houses. They are usually born in manure heaps at chicken farms and piggeries.
But some localised clans of fly are becoming resistant to synthetic pyretheroids, the insecticide normally used by farmers to control them. They are also buzzing merrily past household fly-sprays. The problem is gradually spreading. Flies can travel for hundreds of yards from chicken sheds in search of a country kitchen. Fly- grubs and larvae are also being distributed around the countryside in manure spread over fields.
Dr Philip Howse, Reader in Biology at the University of Southampton, said: 'Most farmers have gone through the whole spectrum of available insecticides by now, and it is likely that many flies are resistant. There are not too many compounds left.'
With recent warm weather flies have been breeding enthusiastically, making the problem highly visible. Pockets of flies in Hampshire have prompted council environmental health officers to seek assistance from the university and the Ministry of Agriculture.
At Droxford, near Winchester, flies no longer drop on demand. One resident said: 'We stopped using fly-sprays because they didn't work. Instead we use fly-papers, but we have to change them every day because they fill up.'
One company investigating alternatives to chemical fly-sprays is hoping to market a fly-trap, using pheromones and patterns to attract the insects on to sticky paper. A small dose of chemical would affect the fly's feet.
Dr Owen Jones, managing director of Agrisense, said: 'After years of spraying into the air to reach the flies, the idea is to bring the insect to the insecticide.'