Browsing by Author "Meseguer, Roberto"
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- Effects of temperature on the fitness of the alfalfa weevil (Hypera postica)Publication . Levi‐Mourao, Alexandre; Madeira, Filipe; Meseguer, Roberto; Pons, XavierTemperature 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 pro- duction 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 stud- ied were temperature dependent. Development was observed at all temperatures. However, postembryonic survival was opti- mal 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 temper- atures increase by 1–2 °C, the number of generations would not change.
- Phenology, population trends and natural enemy complex of Illinoia liriodendri in SpainPublication . Meseguer, Roberto; Madeira, Filipe; Kavallieratos, Nickolas G.; Pons, XavierIllinoia liriodendri (Monell) (Hemiptera: Aphididae) is an Eastern North American native aphid species that infests ornamental tulip trees, Liriodendron tulipifera L. (Magnoliales: Magnoliaceae), in many localities of Spain and southern Europe. This is a comprehensive three-year study on the biology and ecology of the aphid, where its life cycle, phenology, population dynamic trends, comfort damages, natural enemy complex and its potential to control aphid populations have been investigated for the first time in Europe. The monoecic-holocyclic annual cycle of I. liriodendri has been demonstrated. The highest infestation levels were recorded in May and June, but infestation severity varied among localities. No clear trend regarding the effect of planting site (pit vs. ground) on aphid abundance was observed. A strong positive relationship between the aphid infestation severity and the honeydew dripping was recorded. There was a wide complex of natural enemies associated with the aphid. Coccinellidae were the most abundant predators (< 95%) and showed a positive numerical response to the aphid infestation. Several parasitoid species (mainly Hymenoptera: Aphidiinae and Hymenoptera: Aphelinidae) were found parasitizing I. liriodendri in Spain. The role of natural enemies as agents for controlling the aphid populations is discussed.