Carrot rust fly (Psila rosae) temperature model

Description of the model

The warning system model «Carrot rust fly temperature» is based on a Finnish temperature-based model (Markkula et al, 1998; Tiilikkala & Ojanen, 1999; Markkula et al, 2000). The model determines the start of the flight period for the 1st and 2nd generation of carrot rust fly based on accumuleted degree-days (day-degrees) over a base temperature of 5,0 °C. VIPS uses the model for the 1st generation only.

Standard air temperature (temperature measured 2 m above ground) is used in the model. Degree-days are defined for this model as the sum of the difference between a base temperature of 5,0 °C and the mean temperature for all days with a temperature >5,0 °C, in other words (daily mean temperature – 5,0 °C) from 1 March (beginning when the ground has thawed).

Interpretation of the warning

Green rectangles indicate that the flight period has not yet begun. The accumulated day-degrees are < 260 degree-days (day-degrees).

Yellow rectangles indicate that the flight period is beginning and that flies can be coming into the field. The accumulated day-degrees are ≥ 260 degree-days (day-degrees).

Red rectangles indicate peak flight period. The accumulated day-degrees are ≥ 360 degree-days (day-degrees).

Grey rectangles indicate that the flight period of the 1st generation is over. The accumulated day-degrees are ≥ 560 degree-days (day-degrees).

Be aware that in areas with field covers (plastic, single or double non-woven covers, etc.) with early crops the preceding season (either on the current field or neighboring fields), the flight period can start earlier due to higher soil temperature under the covers.

The graphic presentation shows the progress of the day-degree calculation that is the basis for the green, yellow and red warnings (the line: «Accumulated day-degrees with the base temperature of 5 degrees C»). The graph show straight horizontal lines for the threshold values. «Day-degree threshold for low likelihood of attack» corresponds to when the warning changes from green to yellow (260 day-degrees). «Day-degree threshold for high likelihood of attack » corresponds to when the warning changes from yellow to red (360 day-degrees). «Day-degree threshold for end of flight period» corresponds to when the warning changes from red to grey (560 day-degrees) and the flight period for the 1st generation is considered to be over. When the line « Accumulated day-degrees with the base temperature of 5 degrees C» intersects one of the lines for the day-degree threshold, the warning will advance to the next level and the color of the warning rectangle will change. The graph also shows the daily mean temperature for the relevant weather station. The graph is dynamic and the user can choose which parameters that are shown by clicking on the explanation below the graph.

Warning season – start and end of the warning

Starting time: Shown in VIPS from 1 April (starting date for accumulation of degree-days beginning from when the ground has thawed).
Ending time: When the model has reached the requirement for the end of the flight period for the 1st generation (560 day-degrees).

Testing and validation of the model

National

The model has been tested for Norwegian conditions in the period of 2011-2015. Validation has shown that the model was accurate for most locations for the 1st generation. The model was, however, inaccurate for the 2nd generation for many locations and was totally incorrect for the district of Jæren. Based on the validation results, we have therefore chosen to remove warning of the 2nd generation of carrot rust fly from this model.

International

The model is in use in Finland. The extent to which the model has been validated in Finland is uncertain, but a validation was done in the summer of 1997. This validation showed that the model was quite accurate, but that the threshold temperature sm should be lowered to 255 day-degrees for the start of the flight period (as opposed to 260 degree-days in the original model) and 355 degree-days forthe peak flight period (as opposed to 360 degree-days in the original model) (Tiilikkala & Ojanen, 1999).

Literature

Markkula, I., H. Ojanen and K. Tiilikkala. 1998. Forecasting and monitoring of the carrot fly (Psila rosae) in Finland. The 1998 Brighton Conference: Pests and Diseases: Conference Proceedings, Volume 2, pages 657-662.

Tiilikkala, K. and H. Ojanen. 1999. Use of a geographical information system (GIS) for forecasting the activities of carrot fly and cabbage root fly. IOBC/WPRS Bulletin 22 (5): 15-24.

Markkula, I., A. Hannukkala, A. Lehtinen, I. Mattila, H. Ojanen, S. Raisjio, P. Reijonen and K. Tiilikkala. 2000. Pest warnings and forecasts sent as SMS messages from models into "farmer's pocket". In publication: Pests & Diseases 2000. Proceedings of an international conference held at the Brighton Hilton Metropole Hotel, UK, 13-16 November 2000. BCPC Conference Proceedings pages 285-290.

 

Contacts

Annette Folkedal Schjøll annette.folkedal.schjoll@nibio.no
Tor J. Johansen tor.johansen@nibio.no

Links for more information (Norwegian only)

Plantevernleksikonet/gulrotflue https://www.plantevernleksikonet.no/l/oppslag/62/

Plantevernguiden/gulrotflue: http://www.plantevernguiden.no/index.jsp?hideAlert=true&crop1=10&crop2=1_406&pest1=3&pest2=1_62&preparation1=-1&action=search&searchString

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