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Keywords:

  • biocontrol;
  • development;
  • maturation;
  • photoperiod;
  • temperature;
  • tomato bug

Abstract

The zoophytophagous plant bug Nesidiocoris tenuis (Reuter) is increasingly used for biological control of various agricultural pests. Its native range includes Southern Europe, North Africa, Southern and South-Eastern Asia, although only the Mediterranean strains have been studied experimentally. We investigated effects of temperature and photoperiod on nymphal survival and development, rate of female maturation and egg load in two strains of N. tenuis originating from temperate and subtropical regions of South-Eastern Asia: the ‘Temperate strain’ (from Suwon, Republic of Korea, yearly average air temperature is 13.3°C) and the ‘Subtropical strain’ (from Miyazaki, Japan, yearly average air temperature is 18.2°C). Nymphs and adults were reared on tomato leaflets and fed with eggs of the grain moth Sitotroga cerealella under four temperatures (15, 20, 25 and 30°C) and three photoperiods (10, 12 and 14 h of light per day). In spite of long-term (40–50 generations) rearing under constant laboratory conditions, the studied strains still show a correlation between thermotolerance indices and climate at origin. In particular, at the low temperature of 15°C, survival of nymphs of the Temperate strain was double that of the Subtropical strain, whereas at the higher tested temperatures, survival of the Subtropical strain was not significantly different or even was higher than that of the Temperate strain. The duration of nymphal development in the Temperate strain was significantly shorter than that in the Subtropical strain at 15–25°C, but not at 30°C. In both strains, nymphal survival, duration of nymphal development and rate of female maturation were not significantly dependent on photoperiod, and diapause was not observed under any conditions tested. We conclude that the Subtropical strain of N. tenuis is better adapted to high temperatures, whereas the Temperate strain is more promising for application in greenhouses at medium and low temperatures.