CARROT FLY FORECASTS 2010

We're using a new source of weather data this year and using data from in-field weather stations - supplied by Plantsystems (except for Wellesbourne where the data come from the Met Station). Although the number of sites will be considerably less than in previous years, the weather stations will be in locations that are more appropriate for commercial vegetable production (the location of Met Office sites is determined by other factors). It is also the 'type' of weather data that growers would use if running MORPH for themselves, so should give us more experience of a commercial situation.

Control - The timing of foliar sprays of pyrethroids is critical. They should be targeted against the adults and the aim should be to kill female flies before they lay eggs, since most pyrethroid insecticides are ineffective in the soil. The flies are killed either by direct contact with the insecticide or by contact with insecticide residues on the crop foliage. The best time to apply sprays to kill flies by direct contact is between 4 pm and 6 pm, when maximum numbers of female flies are in the crop.

The table below shows the output for the forecasts. We have used historical data (at present from 2008) to project the forecasts forwards beyond the date when data for the current year are available.

Carrot fly forecasts 2010 - weather data up to 26 September 2010 

There is an apparent discrepancy between the Wellesbourne forecast - which uses the 'old' type of data and the other forecasts which use the new type. Some of the forecasts, particularly the Scottish one, seem quite 'late'. Please bear this in mind when interpreting the information. Apologies for any confusion.

Third generation - some third generation flies may emerge in late September at sites towards the south. However, declining temperatures during October will slow development, meaning that some flies may not lay eggs, and even if eggs are laid, the eggs are unikely to develop sufficiently to hatch. HDC-funded studies a number of years ago indicated that the risk of new carrot fly larvae hatching decreased considerably after the end of September and that the damage that develops on carrot crops during the winter is due to late-developing second generation larvae which continue to feed.

The graph below shows forecasts of carrot fly EGG-LAYING for five sites - as above.

The graph below shows the forecast pattern of egg-laying by female carrot flies at Wellesbourne in 2010 and compares it with captures on sticky traps. The first set of traps was in the overwintered carrot crop and fly numbers declined as the flies moved off to our new carrots (traps removed 25 May). There is a second set of traps in the new carrots (from 18 May).

Information on control of carrot fly with foliar sprays of pyrethroids is in HDC Factsheet 08/01 - 'Insecticidal control of carrot fly' - available from the HDC.  

Follow this link to the output from a recent EPPO workshop on carrot fly control

CARROT FLY - trap captures at Wellesbourne in 2005

Sticky trap in our carrot plot at Wellesbourne - May 2006

CARROT FLY - trap captures at Wellesbourne in 2006

CARROT FLY - activity at Wellesbourne in 2008

CARROT FLY - trap captures at Wellesbourne in 2009