SCIENTISTS at the Institute of Arable Crop Research in Rothamsted are predicting the early appearance of greenfly yet again this spring, due to another unseasonably mild winter.

Professor Richard Harrington, one of the principal research scientists at the institute, based in Harpenden, has been collecting data on greenfly in order to come up with the best methods of pest control.

The institute has been collecting data on greenfly since 1965, along with a number of other European countries.

Professor Harrington said: "When you have a really long-term set of data as we have, then you can look at the patterns that are emerging in depth and determine just what is making aphids do what they do."

He said that in the past few years, greenfly have been arriving progressively earlier and he puts this down to the fact that the temperature has been at least a couple of degrees higher than the average.

The 1990's saw some of the mildest winters on record.

This means that this year we could see the arrival of the pests as soon as early April.

The findings will be used to help formulate the best ways of controlling the pests, focusing specifically on the needs of agricultural crops.

Professor Harrington said: "If we have some idea of when things are going to happen then we can determine whether the flies need to be treated with pesticides.

"One of our central concerns is that we don't resort to the use of pesticides for greenfly control unless it is absolutely necessary."

The institute is responsible for compiling the database, which records findings from 15 different scientific and crop centres across the country.

The project also collaborates with similar aphid data collections across Europe.

It has also recently applied to extend the scheme so that it can include some of the newly associated EU member states such as Lithuania, making the data network even more extensive.