Pest Management Science (2022) 78, 4223-4233

Alexandre Levi-Mourao, Filipe Madeira, Roberto Meseguer and Xavier Pons (2022)
Effects of temperature on the fitness of the alfalfa weevil (Hypera postica)
Pest Management Science 78 (10), 4223-4233
Abstract:
Background
Temperature directly influences the survival, development and reproduction of insects and limits their biological activity. The alfalfa weevil (Hypera postica Gyllenhal) is a destructive pest of alfalfa crops in Spain and in most of the alfalfa production countries. The knowledge of how temperature affects the fitness of this pest can be used to predict its activity in current or forecasted environmental conditions and to develop more accurate control strategies.
Results
We evaluated the fitness of alfalfa weevil at eight constant temperatures (8–36 °C) at 4 °C intervals by using life tables and models for the description of temperature-dependent development rates. We found that most of the parameters we studied were temperature dependent. Development was observed at all temperatures. However, postembryonic survival was optimal at 16 °C but very low at 36 °C. Adults did not reproduce at 8, 32 or 36 °C. The highest fecundity and net reproductive rate were observed at 20 °C, but the highest intrinsic rate of increase occurred at 24 °C. We predicted the phenology of the pest based on the heat needed for development, the cumulative degree days from the beginning of October to the end of May, and the day length in the study region.
Conclusion
Our prediction was validated using field data reporting the first occurrence of larval instars and adults, revealing that no more than two generations are possible within an annual cycle. In a hypothetical case where average monthly temperatures increase by 1–2 °C, the number of generations would not change.
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Database assignments for author(s): Filipe Madeira, Xavier Pons

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Hypera postica	Alfalfa/lucerne (Medicago sativa)	Spain (continental)