Performance of four Trichogramma species (Hymenoptera: Trichogrammatidae) as biocontrol agents of Heliothis virescens (Lepidoptera: Noctuidae) under various temperature regimes

Abstract

Trichogramma spp. are major parasitoids of lepidopteran pest eggs, but there is large variation in efficacy toward a given pest among the numerous described Trichogramma species. It is important to select the Trichogramma species that most effectively parasitize and develop in target pest eggs for biological control. In this context, Trichogramma pretiosum, T. exiguum, T. atopovirilia and T. acacioi were studied in Heliothis virescens eggs under different thermal conditions. The parasitoids were reared at constant temperatures of 20, 25 and 30°C and tested at these respective temperatures, while parasitoids reared at 25°C were also tested at 20 and 30°C, for a total of 20 species-temperature combinations. About 30 H. virescens eggs were offered to the parasitoids for 24 h. Among the four species, parasitism rate by T. atopovirilia was highest at all temperature conditions, whereas T. acacioi had the lowest rates of parasitism at 25°C and 25/30°C. Parasitism ranged from 13.8 to 43.8% among all species-temperature combinations. Viability (emerged parasitoids) ranged from 80.8 to 98.4%, and was deemed satisfactory. The emergence rates of T. exiguum and T. acacioi were affected by temperature. Temperature also affected the sex ratio of T. exiguum at 25/30°C, whereas T. pretiosum and T. acacioi produced females predominantly independent of temperature. Overall, the parasitoid T. atopovirilia was the most efficient in parasitizing H. virescens eggs, though the levels of parasitism obtained might not ensure its successful use in biological control programs. The temperature-related differences in biological traits observed in the four Trichogramma species tested hint at the importance of making careful choices regarding climatic conditions where the parasitoid is going to be used when selecting a species for biological control programs.

Refrigerated Eggs of Riptortus pedestris (Hemiptera: Alydidae) Added to Aggregation Pheromone Traps Increase Field Parasitism in Soybean

“…Emergence of Trichogrammatidae parasitoids per parasitized egg in our experiments (1.0006 ± 0.0002) was low compared with reports by Andrade et al (2011) (Oliveira et al 2000;Soares et al 2007). Larger eggs are the most important factor involved in allowing the emergence of more individuals per host (Andrade et al 2011).…”

“…Larger eggs are the most important factor involved in allowing the emergence of more individuals per host (Andrade et al 2011).…”

Trichogramma parasitoids for control of Lepidopteran borers in Taiwan: species, life‐history traits and Wolbachia infections

“…These borers are difficult to control with chemical approaches because their larvae reside in the stem and thereby avoid contact (Cheng 1997;Ko et al 2014). In addition, there are concerns about the broader harmful effects of insecticides on beneficial arthropods (Suma et al 2009;Andrade et al 2011;Baron et al 2014). As in other countries (e.g.…”

“…Biological control is a key component of integrated pest management programmes in combination with selective pesticide use, and information on interactions between natural enemies, hosts and other abiotic factors is required to optimally select biological control agents Andrade et al 2011;Ragsdale et al 2011;Chailleux et al 2014). Important beneficial species in the biological control of lepidopteran pests are the Trichogramma (Hymenoptera: Trichogrammatidae), minute polyphagous endoparasitoids of insect eggs, are used against a variety of crop pests throughout the world including those of sugar cane and corn in south-eastern Asia.…”

Assessing the Total Mortality Caused by Two Species of Trichogramma on Its Natural Host Plutella xylostella (L.) at Different Temperatures

“…Temperature affects important biological traits of Trichogramma species (Kalyebi et al 2005, Andrade et al 2011, Yuan et al 2012. Species and strains of Trichogramma can differ in the extent to which they respond to temperature, which may contribute to their success as biocontrol agents (Thomson et al 2001).…”