Heat and Cold Shocks Decrease the Incidence of Diapause in Trichogramma telengai Larvae

Area of Science:

• Entomology
• Insect Physiology
• Stress Biology

Background:

• Insect diapause is a crucial adaptation for surviving adverse conditions.
• Understanding thermal stress effects on diapause is vital for insect management.
• The influence of thermal shocks on diapause incidence remains underexplored.

Purpose of the Study:

• To investigate the impact of cold and heat shocks on facultative larval winter diapause in *Trichogramma telengai*.
• To differentiate the mechanisms by which thermal shocks affect diapause incidence.
• To provide insights for optimizing *Trichogramma* mass rearing and storage.

Main Methods:

• Laboratory experiments exposing *Trichogramma telengai* larvae to cold (-10 °C) and heat (43 °C) shocks.
• Assessing the incidence of facultative larval winter diapause following thermal stress.
• Analyzing developmental stage-specific sensitivity to thermal shocks.
• Evaluating the influence of shocks on diapause-destined vs. non-diapause-destined individuals and differential mortality.

Main Results:

• Both cold and heat shocks (≥20-30 min) significantly reduced diapause incidence in *T. telengai*.
• Heat shock sensitivity peaked in mid-stage larvae (5 days at 15 °C), while cold shock sensitivity peaked in late-stage larvae (9-11 days at 15 °C).
• Heat shocks primarily altered the proportion of diapause-destined individuals, whereas cold shocks mainly acted through differential mortality favoring non-diapause individuals.

Conclusions:

• Thermal shocks exert significant, yet distinct, influences on insect diapause incidence.
• The timing of thermal stress and the specific shock type critically determine the outcome on diapause.
• Findings enhance understanding of insect stress responses and inform practical applications in *Trichogramma* biological control programs.