Rich diversity of RNA viruses in the biological control agent, Orius laevigatus.

Orius laevigatus (Hemiptera, Anthocoridae) is a generalist predator extensively used for the biocontrol of diverse agricultural pests. Previous studies on O. laevigatus have focused on the improvement of insect genetic traits, but little is known about its association with microbes, especially viruses that may influence its production and efficacy. More than 280 RNA viruses have been described in other Hemiptera insects, in line with the continuous discovery of insect-specific viruses (ISVs) boosted by next-generation sequencing. In this study, we characterized the repertoire of RNA viruses associated with O. laevigatus. Its virome comprises 27 RNA viruses, classified within fourteen viral families, of which twenty-three viruses are specific to O. laevigatus and four are likely associated with fungal microbiota. The analysis of viral abundance in five O. laevigatus populations confirmed the presence of simultaneous viral infections and highlighted the ubiquitous presence and high abundance of one solinvivirus and three totiviruses. Moreover, we identified 24 non-retroviral endogenous viral elements (nrEVEs) in the genome of O. laevigatus, suggesting a long-term relationship between the host and its virome. Although no symptoms were described in the insect populations under study, the high diversity of viral species and the high abundance of certain RNA viruses identified indicate that RNA viruses may be significant for the applicability and efficacy of O. laevigatus in biocontrol programs.

Inheritance and Biological Characterization of an Orange-nymph Mutant in Orius laevigatus (Hemiptera: Anthocoridae).

A mutation showing a distinct orange color in the nymph stages was found in Orius laevigatus (Fieber) (Hemiptera: Anthocoridae), a key biological control agent in protected crops, used to control small pests, especially thrips. A laboratory strain carrying this body color mutation ambar was established. Genetic analysis determined that the mutation (ambar) was controlled by a single autosomal recessive allele. Some biological and ecological characteristics of this orange strain were compared to a normal population. Longevity, fecundity and fertility were similar in both populations, but immature survival, development rate, body size, starvation tolerance and predation capacity were inferior in the orange strain. The utility of the orange mutant as a visible marker for biological and ecological studies of this important biological control agent is discussed.

Effect of Parental Age and Mating Status on Reproductive Performance of Orius laevigatus (Hemiptera: Anthocoridae).

The reproductive potential of biological control agents (BCAs) is crucial for efficient mass-rearing and field performance, and it all begins with mating. Fecundity can be strongly influenced by intrinsic conditions, such as female age and, often neglected, male age and mating status. However, little is known about the impact of parental status at mating on female reproductive outcomes in BCAs. Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is widely used to control thrips in protected crops. We evaluated how many consecutive females a male could successfully mate and the effect on a female's reproductive output. In addition, we studied the effects of male and female age on mating. In the multiple mating experiment, the males showed a high capacity to fertilize females successively, not reducing fecundity until the sixth mated female. In the delayed mating experiment, copulation duration and fecundity increased with male age but decreased with female age. In contrast, fertility followed an opposite pattern, increasing with female age but decreasing with male age. However, fecundity gains outweighed fertility declines in both sexes. Therefore, reproductive capacity is increased when mating newly emerged females with males a few days old. The implications of our results for mass rearing and field performance are discussed.