Unseasonally dry, mild weather during April and at the beginning of May has resulted in much earlier sightings of a wider range of crop pests, according to United Agri Products (UAP), a leading distributor of crop protection products.

"As a general rule we either have a 'pest year' or a 'disease year' in the UK. To date, it has been too dry in the South East for much disease to develop and 2007 is shaping up to be a pest year," explains UAP's Vegetable Technical Manager Chris Wallwork.

"Many species are being seen in increased numbers, much earlier than last year. A good example is the mealy cabbage aphid. The first ones normally first migrate to brassica crops in mid-May in the South of England, but this year the first sightings in Kent were during mid-April, a month early. The Rothamsted suction trap network also recorded some individuals of Myzus persicae as early as January, which is exceptionally early. Although they were not present in sufficient numbers to be of any economic significance at that stage, they are now."

"Weather conditions have tended to be more evenly spread throughout the country this year, with the East very dry and the West drier than usual. As a result, pests are moving north from the South East earlier, and small colonies of mealy aphids have already been seen on brassicas in Lincolnshire. Less common pest species have also been sighted. For example, UAP agronomists have seen visible damage from springtails in early, fleece-covered lettuce. In most seasons, we expect to see springtails under the fleece covering, but no damage. The fact that there is less decaying materials in the soil this year because it has been so dry may mean that springtails are being forced to feed on the crop itself.

"The other side of the coin is that the un-seasonal weather has produced an abundance of beneficials such as parasitic wasps and lacewings, the larvae of which are a major aphid predator. In previous years, large numbers of aphids and aphid-predators early in the season have been followed by a crash in populations later in the season. It would be dangerous to predict that will automatically be the case this year, but growers should, where possible, favour the use of products that have the least impact on them.

"Products and treatment advice are shifting towards the need to maintain populations of beneficials and UAP agronomists always take this into consideration when making recommendations. The use of beneficial-friendly materials has long been the case in the top fruit sector, then spread into soft fruit and is becoming more widespread in the vegetable and arable sectors. It will become more important in the future as the number of aphids with resistance to older insecticides increases."

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