The use of Telenomus remus (Nixon, 1937) (Hymenoptera: Scelionidae) in the management of Spodoptera spp.: potential, challenges and major benefits

Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae), also known as fall armyworm (FAW) is a polyphagous pest which can cause significant losses and is considered a global threat to different crops and a risk to food security. Currently, in maize, the pest is predominantly controlled by pesticides or transgenic events. However, the use of biological control agents is considered the most sustainable and preferred method of control, providing high effectiveness. Among the various natural enemies reported for FAW, the egg parasitoid Telenomus remus has gained most interest, and has been mass released against FAW in the Americas for many years. In addition to FAW, other armyworms of the genus Spodoptera often cause high crop damage and may be controlled using T. remus. Among other important aspects, this paper presents a review on T. remus mass rearing techniques, estimated costs of mass production, and release strategies. Due to the recent invasion of FAW in Africa, Asia, and Australia T. remus provides good opportunities for the establishment of an augmentative biological control program, reinforcing sustainable production of major crops such as maize in affected countries.

Non-target effects of ten essential oils on the egg-parasitoid Trichogramma evanescens

Essential oils (EOs) are increasingly used as biopesticides due to their insecticidal potential. This study addresses their non-target effects on a biological control agent: the egg parasitoid Trichogramma evanescens. In particular, we tested whether EOs affected parasitoid fitness either directly, by decreasing pre-imaginal survival, or indirectly, by disrupting parasitoids' orientation abilities. The effect of Anise, Fennel, Sweet orange, Basil, Coriander, Oregano, Peppermint, Mugwort, Rosemary and Thyme EOs were studied on five strains of T. evanescens. Specific experimental setups were developed, and data obtained from image analysis were interpreted with phenomenological models fitted with Bayesian inference. Results highlight the fumigant toxicity of EOs on parasitoid development. Anise, Fennel, Basil, Coriander, Oregano, Peppermint and Thyme EOs are particularly toxic and drastically reduce the emergence rate of T. evanescens. Most EOs also affect parasitoid behavior: (i) Basil, Coriander, Oregano, Peppermint, Mugwort and Thyme EOs are highly repellent for naive female parasitoids; (ii) Anise and Fennel EOs can have repellent to attractive effects depending on strains; and (iii) Sweet orange, Oregano and Rosemary EOs have no detectable impact on orientation behavior. This study shows that EOs fumigation have non-target effects on egg parasitoids. This highlights the need to cautiously precise the deployment framework of biopesticides in an agroecological perspective.

Use of Pyriproxyfen to Induce Oogenesis in Diapausing Megacopta cribraria (Heteroptera: Plataspidae), and Evaluation of Pyriproxyfen-Induced Eggs for Rearing the Parasitoid Paratelenomus saccharalis (Hymenoptera: Scelionidae)

The mass rearing of hymenopteran egg parasitoids requires an abundant supply of host eggs. The onset of reproductive diapause and subsequent decline in egg production poses a challenge for parasitoid rearing when using host colonies augmented by field-collected insects. We investigated the application of pyriproxyfen, a juvenile hormone analog, to induce oviposition in diapausing adult kudzu bugs, Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae), and the use of eggs produced by pyriproxyfen-treated kudzu bugs to rear the egg parasitoid, Paratelenomus saccharalis (Dodd) (Hymenoptera: Scelionidae). The effects of pyriproxyfen and photoperiod treatments on host mortality, egg production, and rates of parasitoid eclosion from the eggs were used to calculate the parasitoid yield for the different treatment regimes. A combination of pyriproxyfen and a long-day photoperiod increased the parasitoid yield by 87% compared to acetone and a long-day photoperiod. The general applicability of JH-analog mediated egg production for parasitoid rearing is discussed.

Effects of Wolbachia Infection, Parasitic Order, And Time Interval On The Outcome of Inter-Strain Intrinsic Competition Between Bisexual Strain And Wolbachia-Induced Thelytokous Strain of Egg Parasitoid, Trichogramma Dendrolimi

Parasitoids may deposit a second clutch of eggs on a host that has been parasitized by the same parasitoid species. This is termed “superparasitism”. Wolbachia infection increases the superparasitism frequency of Trichogramma females. We investigated the outcome and fitness cost of inter-strain intrinsic competition between Wolbachia-infected thelytokous strain (TDW) and uninfected bisexual strain (TDB) of Trichogramma dendrolimi. To determine the developmental rate of both strains, the size of immature stages of T. dendrolimi offspring at different times after parasitization was measured in single parasitism and superparasitism conditions. The results showed increased superparasitism by Wolbachia-infected females compared to uninfected females, regardless of the time interval between oviposition; Trichogramma females were unable to distinguish between host eggs previously parasitized by TDB or TDW females. When the first oviposition was performed by TDB females, the TDB offspring outcompeted TDW offspring deposited later. However, although the TDW offspring was deposited 8 h earlier than the TDB offspring, it gained no advantage over TDB offspring. Regardless of parasitism conditions, the differences in development rate and time between TDW and TDB offspring were not significant. This study revealed that albeit TDW females presented a higher tendency of superparasitism than TDB females, TDB offspring outcompeted TDW offspring even when the latter was deposited 8 h earlier. The negative effects of Wolbachia infection on the competitive ability of TDW offspring inside the host eggs were due to offspring’s low fitness rather than delayed development.

Psix striaticeps (Dodd) (Hymenoptera, Scelionidae): an Old World parasitoid of stink bug eggs arrives in Florida, USA

Psix striaticeps (Dodd) is an egg-parasitoid wasp previously known only from the Old World. We report this species from twelve counties in Florida, which are the first records in the Western Hemisphere. It was collected in yellow cylinder traps and reared from the eggs of three stink bug species: Nezara viridula L., Chinavia marginata (Palisot de Beauvois), and Piezodorus guildinii (Westwood). A COI barcode analysis found a 100% match between the Floridian population and a specimen from South Africa. The prospects of using Ps. striaticeps as a biological control agent against exotic stink bugs are discussed.

Identification and expression of odorant binding proteins in the egg-parasitoid Trissolcus basalis (Wollaston) (Hymenoptera, Scelionidae, Telenominae)

Trissolcus basalis (Wollaston) (Hymenoptera, Scelionidae) is an egg-parasitoid of the southern green stink bug, Nezara viridula (Linneaus) (Hemiptera, Pentatomidae). Many behaviors associated with female T. basalis host-finding and acceptance are mediated by chemosensory pathways, for which olfactory, gustatory and ionotropic receptors have been previously identified. Odorant binding proteins (OBPs) are small, globular proteins, one of the functions of which is the transport of odorant ligands through the aqueous lymph of chemosensory sensilla to these receptors. We identified 18 classical OBP sequences in the T. basalis genome and transcriptomes sharing an average 26.8% pairwise identity. Gene tree analyses suggest very limited lineage-specific expansion and identify potential orthologs among other scelionids and Hymenoptera. Transcriptome mapping and qPCR comparison of expression levels in antennae and bodies of both sexes determine that at least five TbOBPs are preferentially expressed in the female antennae. These are, therefore, prime candidates for further study to determine their role in detecting host-produced semiochemicals.

First record of Telenomus fariai Costa Lima, 1927 (Hymenoptera, Scelionidae, Telenominae) as a parasitoid of Triatoma dimidiata (Latreille, 1811) (Hemiptera, Reduviidae, Triatominae) eggs in Mexico

The egg parasitoid Telenomus fariai Costa Lima (Hymenoptera, Scelionidae), is reported for the first time in Veracruz, Mexico. Telenomus fariai was discovered in 2019 during a field collection of Triatoma dimidiata L. (Hemiptera, Reduviidae), representing the first report of its association with Tr. dimidiata in Mexico. This species is here redescribed and sequencing of a portion of the cytochrome oxidase 1 gene (COI) was performed to facilitate future identifications and to examine host associations between species of Telenomus Haliday and Reduviidae in a broader context.

Stink bug egg parasitoids (Hymenoptera, Scelionidae) associated with pistachio in Iran and description of a new species: Trissolcus darreh Talamas

Surveys for egg-parasitoid wasps were conducted in Rafsanjan, Iran, on two species of Pentatomidae (Hemiptera) found in pistachio orchards, Acrosternum arabicum Wagner and Brachynema signatum Jakovlev. Five species of Scelionidae (Platygastroidea) were recovered, including one that is here described as new: Psix saccharicola (Mani), Trissolcus colemani (Crawford), T. darreh Talamas sp. nov., T. perepelovi (Kozlov), and T. semistriatus (Nees). In addition to describing a new species, we report new host associations, provide COI barcodes for four of these species, and discuss host-related intraspecific variation in T. darreh and T. perepelovi.

Contact Toxicity of Insecticides and Biopesticides to Trichogramma Chilonis Ishii. (Hymenoptera: Trichogrammatidae) under Laboratory Condition

Integration of insecticides and biological controls is an important tactic of Integrated Pest Management (IPM). Trichogramma chilonis is a promising natural enemy of many lepidopteran insect pests. However, this hymenopteran egg parasitoid is adversely affected by most insecticides. Contact toxicity of nineteen insecticides and three biopesticides on adults of T. chilonis was investigated by using dry film residue bioassays under laboratory conditions. Profenofos and chlorpyrifos were highly lethal to the adults even at sublethal doses followed by dimethoate, spinosad, indoxacarb and acephate + imidacloprid. Diafenthiuron, nimbecidine and flubendiamide were categorised as less toxic. The biopesticides viz., Metarhizium anisopliae, Beauveria bassiana and Metarhizium rileyi were found innocuous to T. chilonis. The studysuggests that the insecticides with less toxicity and biopesticides with apparently no harmful effects on the parasitoid can be used in conjunction with parasitoids in IPM programmes. This will also advice the plant protectionists in avoiding the one with detrimental effects on this hymenopteran wasp with appropriate timing of application that controls the pests without adversely affecting their natural enemies

Biology and life table of Trichogramma chilotraeae, Egg parasitoids of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Spodoptera frugiperda is a species of armyworm that attacks maize crops globally and is a dangerous new invasive pest in Indonesia. Biological control, which employs natural enemies, is one method of controlling this pest. One of the natural enemies found in the field is the egg parasitoid of the Trichogrammatidae family. This study aimed to determine the reproductive capacity of the parasitoid on S. frugiperda eggs. The tested parasitoids were collected from S. frugiperda eggs on corn cultivations in Tenjolaya Village, Bogor Regency, West Java Province. The identification results showed that the parasitoid species used in this study was Trichogramma chilotraeae. The development periods of eggs, first instar larvae, second instar larvae, and pupae in the laboratory were 1.16 days, 1.18 days, 1.39 days, and 3.28 days, respectively. The reproductive capacity of T. chilotraeae on S. frugiperda eggs, referred to as the net reproduction rate (Ro), was 28.13, gross reproduction rate (GRR) was 30.43. the average time for one generation (T) was 9.07. The intrinsic rate of increase (r) was 5.54, and Doubling time (DT) was 1.88. Thus, the egg parasitoid of T. chilotraeae was not very effective as a potential biological agent for S. frugiperda.