Abstract
Knowledge of the optimal temperatures for development and survival of biological control agents is essential for efficient mass-rearing and introduction of natural enemies in augmentative biological control programs. We studied the effect of constant and alternating temperatures on development and survival of immature stages and the sex ratio at emergence of adults of the Nearctic generalist predator Geocoris punctipes (Say). We also determined its thermal requirements. They were reared in climatic chambers at alternating (21/11°C, 24/18°C, 27/21°C and 30/26°C ± 1°C) and constant temperatures (16.8°C, 21.5°C, 24.5°C and 28.3°C ± 1°C), RH 70 ± 10% and a 14 h photophase. Survival and development of G. punctipes were the same when reared at constant and alternating temperatures. Five instars were recorded in all temperature regimes. The duration of the egg stage and each instar, as well as that of total larval development were longer, and larval survival lower when reared at 16.8°C, 21/11°C, 21.5°C and 24/18°C than at 24.5°C, 27/21°C, 28.3°C and 30/26°C. The optimal temperature range for development and survival of G. punctipes is 24.5°C to 30°C, its lower development threshold temperature is 13.5°C and its thermal constant 295.9 DD. Sex ratios were not significantly different from 1 : 1 male : female ratio in all temperature regimes. There is an excellent match between the temperature regimes at which the prey Tuta absoluta (Meyrick) and predator G. punctipes are active, which indicates that this predator will function well in crops where this pest is present.
Highlights
Predators of the genus Geocoris are abundant both in nature and agroecosystems (Sweet, 2000)
Individuals were identified under a stereomicroscope using the key to species of Geocoris spp. by Mead (2008): we only found G. punctipes
Adults of G. punctipes were placed in glass pots (1.7 l) containing shredded paper towels, pigweed inflorescences placed in a glass tube (10 mL) with water, and eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae)
Summary
Predators of the genus Geocoris are abundant both in nature and agroecosystems (Sweet, 2000). Based on studies carried out in the laboratory, agricultural fields and natural habitats, Schuman et al (2013) stress the potential of Geocoris spp. as biological control agents. The potential of Geocoris spp. in reducing herbivore populations in crops in the field and greenhouses still remains to be demonstrated. Geocoris punctipes (Say) (Hemiptera: Geocoridae) is a predator of aphids, caterpillars and eggs of various Lepidoptera, Bemisia tabaci (Gennadius) and Lygus spp. on several field crops (Richman et al, 1980; Elvin et al, 1983; Tillman & Mullinix, 2003; Bueno & Zanuncio, 2009; Bueno & van Lenteren, 2012). Geocoris punctipes was sold on a small scale for controlling Lepidoptera during the 1990s in North America (Bueno & van Lenteren, 2012; van Lenteren, 2012)
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