Abstract

The effects of temperature on the melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), preimaginal development, survival, fecundity, longevity of females and males, and population growth were investigated at 16, 19, 22, 25, 28, and 31° C, 70–80% RH, and a photoperiod of 12:12 L:D. The results indicated that the duration of egg, larval, and pupal stages was significantly influenced by increased temperature. The egg-to-adult developmental period of T. palmi declined from 35.7 to 9.6 days as the temperature increased from 16 to 31° C. The developmental threshold temperature estimated for egg-to-adult was 11.25° C, with a thermal constant of 196.1 degreedays. The developmental threshold temperature was 13.91, 11.82, 9.36, and 10.45° C for adult preoviposition period, total preoviposition period, female longevity, and male longevity, respectively. The thermal constants for completing the adult preoviposition period, total preoviposition period, female longevity, and male longevity were 29.3, 227.3, 454.6, and 344.8 degreedays, respectively. Female longevity was found to be shortest at 31° C (18.7 days) and longest at 16° C (56.7 days), and male longevity was shortest at 31° C (15.5 days) and longest at 16° C (50.7 days). Fecundity was highest at 25° C (64.2 eggs/female) and lowest at 16° C (23.4 eggs/female). The population trend index of T. palmi was highest at 25° C (31.3) and lowest at 16° C (7.6). The optimal developmental temperature for T. palmi in eggplant, Solanum melongena L. (Solanales: Solanaceae), was determined to be 25° C.

Highlights

  • Temperature is one of the most critical environmental factors influencing rate of insect growth and development (Taylor 1981)

  • The results showed that the population increased 31.34 times after one generation at 25° C, showing this temperature to be optimal for T. palmi population growth

  • Results from this study indicated that the mean developmental time of different stages of T. palmi declined with increasing temperature

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Summary

Introduction

Temperature is one of the most critical environmental factors influencing rate of insect growth and development (Taylor 1981). The melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), has become one of the most serious pests of eggplant, cucumber, field beans, melons, peppers, and flowers in Taiwan since its arrival in 1979 (Chang 1995). It has been widely distributed around the world in sub-tropical and tropical regions (Cannon et al 2007). Females may lay up to 200 eggs in their two-month life span (Zhang and Brown 2008) Both larvae and adults feed on leaves, flowers, and fruits, and cause scarring and deformities from extensive feeding. Fruits severely damaged by T. palmi have a low marketing value (5–10 NT$/kg) compared to good quality fruits (35–40 NT$/kg) in Taiwan. Capinera (2008) reported that the egg-to-adult developmental time of T. palmi is 16.5 days at 25° C and 42 days at 15° C

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