Impact of temperature on postdiapause and diapause of the Asian gypsy moth, Lymantria dispar asiatica.

Jing Wei,Shao-Wei Shen,Dei-Peng Wang,Juan Shi,You-Qing Luo

doi:10.1093/jis/14.1.5

Abstract

Lymantria dispar asiatica (Vnukovskij) (Lepidoptera: Lymantridae) is one of three gypsy moth subspecies found in East Asia. Understanding the diapause and postdiapause phases of its eggs is important in characterizing its life cycle. The effects of different constant temperatures for different lengths of times on field-collected, postdiapause eggs were tested during the first year. In the second year, the effects of the same treatments on laboratory-raised eggs in diapause were investigated. The effects of temperature on percent egg hatching, time to hatching, and hatching duration were determined. When field-collected eggs were held at 0 and 5°C, they terminated postdiapause within 11 days. The percent hatching tended to decline with an increased duration of exposure at temperatures greater than 5°C. Diapause terminated slowly (> 37 days) and with a high percentage of hatching for postdiapause eggs held at 10°C. There was a positive correlation between temperature and the speed of postdiapause development for field-collected eggs held at constant temperatures between 10 and 25°C. However, the number of days to the first hatch was significantly longer than for eggs treated with lower temperatures before being transferred to 25°C. Freshly oviposited eggs treated at a constant 0 or 5°C for 200 days were unable to develop into pharate larva. However, eggs treated at a constant 20 or 25°C for 200 days developed into pharate larva but did not hatch even after a subsequent chill. This result suggests why L. dispar asiatica is not found in tropical areas and helps us to predict the distribution of the gypsy moth in China.

Highlights

The gypsy moth, Lymantria dispar Linnaeus (Lepidoptera: Lymantridae), consists of three subspecies, the North American/European gypsy moth (L. dispar dispar L), the Asian gypsy moth (L. dispar asiatica Vnukovskij), and the Japanese gypsy moth (L. dispar japonica Motschulsky) (Pogue and Schaefer 2007)
Percent egg hatching For the Liao Ning strain Keywords (LN) strain, the percent hatching at 0 days was significantly lower than for the other treatments (F = 76.74; df = 3, 60; p < 0.01, Table 1)
To study the percent hatching, experiments on the time to hatching and the hatching duration of L. dispar asiatica were conducted at different temperatures and times

Summary

Introduction

The gypsy moth, Lymantria dispar Linnaeus (Lepidoptera: Lymantridae), consists of three subspecies, the North American/European gypsy moth (L. dispar dispar L), the Asian gypsy moth (L. dispar asiatica Vnukovskij), and the Japanese gypsy moth (L. dispar japonica Motschulsky) (Pogue and Schaefer 2007). Lymantria dispar has become an important pest worldwide in temperate forests (Davidson et al 2001; Orozumbekov et al 2009). Diapause allows the species to survive overwintering and enables its eggs to survive for up to 9 months, which accounts for 3/4 of the moth’s annual life (Leonard 1968). Egg hatching is the most critical life-stage event in establishing seasonality of this pest (Gray 2003). These factors are important for the distribution of the L. dispar and have led to several studies focusing on the diapause mechanisms (Bell 1996; Keena 1996; Gray et al 2001)

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Conclusion