Journal of Applied Entomology (2014) 138, 754-762

M. Eickermann, B. Ulber, L. Hoffmann and J. Junk (2014)
Improving phenological forecasting models for rape stem weevil, Ceutorhynchus napi Gyll., based on long-term multisite datasets
Journal of Applied Entomology 138 (10), 754-762
Abstract: New threshold-based models to predict the start of invasion by the stem-boring pest, the rape stem weevil (Ceutorhynchus napi Gyll.) of winter oilseed rape (Brassica napus L.), were developed and compared to published models using long-term datasets on weather and weevil phenology from experimental locations in Germany and Luxembourg. Threshold values for daily records of maximum air temperature, mean soil temperature, sunshine duration and total precipitation were adjusted to local conditions on the date of first weevil migration in spring. Mean error and the root mean squared error were used to assess model quality, where the error is defined as the number of days between predicted and observed arrival of weevils on the crop (regardless of sign). Best model results predicted first crop invasion by rape stem weevil when the thresholds of daily maximum air temperature >7.8°C, mean soil temperature >6.6°C, daily total precipitation <1.0 mm and sunshine duration >1 h were matched. This model takes into account meteorological variables likely to influence conditions at the overwintering site of the weevils in the soil, as well as variables that may limit weevil flight. Adjusted air temperature threshold values were consistently lower for Luxembourg sites than for those optimized for Germany. A simple model relating the date of first weevil invasion to accumulated daily maximum air temperature above 0°C (from 1 January) was also evaluated. This proved less suitable for forecasting crop invasion by C. napi. We suggest that phenological models using locally adjusted meteorological-based thresholds have the potential to offer sufficiently accurate forecasts of first immigration flights by C. napi for appropriate timing of insecticide application. In addition, the developed models are suitable tools to be used in climate change impact studies.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Michael Eickermann, Bernd Ulber, Juergen Junk

Research topic(s) for pests/diseases/weeds:
thresholds/decision-support systems
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ceutorhynchus napi	Rape/canola (Brassica napus)	Germany
	Ceutorhynchus napi	Rape/canola (Brassica napus)	Luxembourg