Effects of temperature on the fitness of the alfalfa weevil (Hypera postica)

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.

Effects of temperature on reproduction and development of Cyanopterus ninghais (Hymenoptera: Braconidae), a larval parasitoid of Monochamus alternatus (Coleoptera: Cerambycidae)

“…Within the suitable temperature range, there is a gradual increase in insect fecundity with increasing temperature. However, once the temperature exceeds the suitable range, it can impede and suppress insect reproduction, by reducing egg production and survival and lengthening the pre‐oviposition period (Janowitz & Fischer, 2011; Levi‐Mourao et al., 2022). These study findings determined the optimal temperature range for reproduction and development of C. ninghais to be 26 to 29°C based on a thorough evaluation of parameters, including its pre‐oviposition period, parasitism rate, offspring number, sex ratio and developmental rate.…”

On-farm harvest timing effects on alfalfa weevil across the Intermountain West region of the United States

“…Early harvest was a common practice for our producer collaborators in the Intermountain West, with some harvesting a full week before historical early harvest recommendations. These shifts to early harvests could be due to various drivers: focusing on quality (i.e., higher nutritive value) rather than yield for particular markets, changes in climate impacting alfalfa and weevil growth rates, or use of newly developed alfalfa varieties ( 36 , 37 ).…”

Polygenic adaptation of a cosmopolitan pest to a novel thermal environment

“…) This trade-off is common in insects (Ffrench-Constant & Bass, 2017). For example, the development and reproduction of insects such as Arma custos (Wang et al, 2022), Trichogramma euproctidis (Tabebordbar et al, 2022), Spodoptera litura (Islam et al, 2022) and Hypera postica (Levi-Mourao et al, 2022) are affected in high-and low-temperature environments. Temperature adaptation is a polygenic trait and genetic redundancy in those genes is necessary (Barghi et al, 2019).…”