Physiological and Biochemical Differences in Diapausing and Nondiapausing Larvae of Eurytoma plotnikovi (Hymenoptera:...

Area of Science:

• Entomology
• Pest Management
• Insect Physiology

Background:

• The pistachio seed wasp (Eurytoma plotnikovi) is a significant pest in Iranian pistachio cultivation.
• Overwintering occurs in the diapausing last instar larval stage.

Purpose of the Study:

• Investigate the link between diapause and cold hardiness in E. plotnikovi larvae.
• Characterize the physiological and biochemical differences between diapausing and non-diapausing larvae.

Main Methods:

• Analysis of digestive α-amylase activity.
• Quantification of glycogen, total simple body sugars, trehalose, myo-inositol, and sorbitol.
• Measurement of lipid accumulation.
• Determination of supercooling points and low-temperature survival rates.

Main Results:

• Digestive α-amylase activity decreased significantly during diapause.
• Glycogen levels decreased while sugars (trehalose, myo-inositol, sorbitol) increased during diapause.
• Lipid reserves accumulated during early diapause and declined later.
• Supercooling points lowered, reaching -23.14°C in January, correlating with higher cryoprotectant concentrations.
• Larvae exhibited maximum cold tolerance from December to February.

Conclusions:

• E. plotnikovi larvae utilize a freeze avoidance strategy.
• Accumulation of specific cryoprotectant compounds (sugars, myo-inositol, sorbitol) is crucial for overwintering survival.