Rearing <Emphasis Type="Italic">Chrysoperla externa</Emphasis> Larvae on Artificial Diets

We tested three artificial diets for rearing larvae of Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae), aiming at reducing the production costs of this predator. Two of the diets come from studies with other species of lacewings, and the third is a modification described in this paper. All diets were based on animal protein and were supplied to 2nd and 3rd instar larvae, whereas 1st instar larvae received eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae). We evaluated the preimaginal duration and survival, adult size, longevity and fecundity, egg hatchability, and predatory capacity of larvae produced. The performance of the diets was followed for seven generations. The diet we describe showed to be the best among the artificial diets tested. Our results show that C. externa can be successfully reared on artificial diets during second and third instars, reducing in 90% the dependency on eggs of A. kuehniella.     

Host suitability of the Mediterranean flour moth for rearing <Emphasis Type="Italic">Meteorus pulchricornis</Emphasis> (Hymenoptera: Braconidae), a polyphagous endoparasitoid of pest lepidopteran larvae

We investigated the host suitability of the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) for a polyphagous koinobiont endoparasitoid Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae), a common natural enemy of various pest lepidopteran larvae. The estimated probability of adult wasp emergence was 80% or higher when eggs were laid in nearly fully grown larvae of E. kuehniella (fresh weight, >?20.0 mg). The body size of emerged adult wasps increased with the initial weight of the host larvae at oviposition. The fresh weight of adult wasps reared on E. kuehniella was approximately 60% of that when reared on a natural host Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), and the lifetime fecundity of wasps reared on E. kuehniella was approximately half of that when reared on S. litura. Ephestia kuehniella was shown to be a positive host candidate for the mass rearing of M. pulchricornis, but further investigation is needed to increase the body size of wasps for more practical use of this species as a biocontrol agent.     

Bt Proteins Have No Detrimental Effects on Larvae of the Green Lacewing, <Emphasis Type="Italic">Chrysopa pallens</Emphasis> (Rambur) (Neuroptera: Chrysopidae)

Biosafety of a genetically modified crop is required to be assessed prior to its commercialization. For this, a suitable artificial diet was developed and used to establish a dietary exposure test for assessing the toxicity of midgut-active Bt insecticidal proteins on Chrysopa pallens (Rambur). Subsequently, this dietary exposure test was used to evaluate the toxicity of the proteins Cry1Ab, Cry1Ac, Cry1Ah, Cry1Ca, Cry1F, Cry2Aa, Cry2Ab, and Vip3Aa on C. pallens larvae. Temporal stability, bioactivity, and the intake of the insecticidal proteins were confirmed by enzyme-linked immunosorbent assay and a sensitive-insect bioassay. The life history characteristics, such as survival, pupation, adult emergence, 7-day larval weight, larval developmental time, and emerged male and female fresh weights remained unaffected, when C. pallens were fed the pure artificial diet (negative control) and the artificial diets containing 200 μg/g of each purified protein: Cry1Ab, Cry1Ac, Cry1Ah, Cry1Ca, Cry1F, Cry2Aa, Cry2Ab, or Vip3Aa. On the contrary, all of the life history characteristics of C. pallens larvae were adversely affected when fed artificial diet containing boric acid (positive control). The results demonstrate that diets containing the tested concentrations of Cry1Ab, Cry1Ac, Cry1Ah, Cry1Ca, Cry1F, Cry2Aa, Cry2Ab, and Vip3Aa have null effects on C. pallens larvae. The outcome indicates that genetically modified crops expressing the tested Bt proteins are safe for the lacewing, C. pallens.     

Toxicity of Secondary Metabolites from Meliaceae Against <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis> (J. E. Smith) (Lepidoptera: Noctuidae)

The study was carried out to evaluate the bioactivity of secondary metabolites from Trichilia pallida, Trichilia pallens, and Toona ciliata against fall armyworm Spodoptera frugiperda (J. E. Smith) larvae. The studied compounds included (+/?)-catechins, a triglyceride, and cedrelone isolated from T. ciliata branches, fruits, and stems, respectively; dammaradienol isolated from T. pallida leaves; and scopoletin isolated from T. pallens branches. The compounds’ activity was evaluated through ingestion and topic treatment. Treated artificial diet was offered to first instar larvae to evaluate ingestion effect, while an application on the dorsal thoracic region of third instar larvae was used to evaluate the topic effect. Mortality was assessed daily, and larval weight was recorded after 7 days for ingestion and 5 days for topic application. Scopoletin and triglyceride caused low mortality rates and reduction in larval weight by ingestion, (+/?)-catechins caused larval weight reduction by ingestion, and scopoletin reduced survival by topic treatment. The most effective compound was cedrelone that affected larval survival and development mainly by ingestion. The estimated LC₅₀, LC₉₀, and EC₅₀ for cedrelone were 0.0365, 0.0659, and 0.0095%, respectively. Further, cedrelone-treated corn leaf discs were offered to fourth instar larvae during 16 h in choice and no-choice tests. The deterrence indexes obtained in the choice tests were 23.5 and 36.3% at concentrations of 0.0365 and 0.0659, respectively. Consumption of cedrelone-treated leaf discs at the concentration of 0.0659% was lower compared to the control in the no-choice test. Thus, cedrelone caused lethal and sublethal effects and phagodeterrence on S. frugiperda and should be further studied.     

Rate of consumption,biological parameters,and population growth capacity of <Emphasis Type="Italic">Orius laevigatus</Emphasis> fed on <Emphasis Type="Italic">Spodoptera exigua</Emphasis>

Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is already successfully used to control Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) in protected crops. In the present work, the predatory capacity of O. laevigatus on the eggs and larvae of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) as well as the population growth capacity of O. laevigatus fed on eggs of the noctuid were determined. Fourth and 5th instar nymphs had a greater consumption of eggs than younger ones. Females consumed more eggs than males. Only 5th instar nymphs and adults preyed on the neonatal larvae of S. exigua. The intrinsic rate of natural increase did not differ between O. laevigatus fed with S. exigua eggs and those offered eggs of the substitute host Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae). Thus, O. laevigatus is a good candidate for the biological control of S. exigua, a cosmopolitan pest of many crops.     

Soybean defense induction to <Emphasis Type="Italic">Spodoptera cosmioides</Emphasis> herbivory is dependent on plant genotype and leaf position

Plants have evolved a diverse array of defensive mechanisms against biotic and abiotic stresses, which can be either constitutive or inducible. Variation in plant-intrinsic factors such as the genotype and the leaf position coupled with insect herbivory can affect the expression of resistance to insects. We investigated if soybean defense induction triggered by Spodoptera cosmioides herbivory varies in function of the genotype and leaf position. This hypothesis was tested in two bioassays using leaf discs or entire leaflets collected from the upper and lower trifoliates of S. cosmioides-injured and uninjured V3-V4 soybean plants. We used one genotype that was constitutively resistant and one that was constitutively susceptible to S. cosmioides based on previous screening. Third-instar larvae were fed one of the treatments and assayed for leaf consumption, larval growth, and efficiency of conversion of ingested food. Genotype and leaf position significantly interacted with herbivory and affected soybean-induced resistance to S. cosmioides. Negative responses on S. cosmioides larvae consumption and growth rates were only observed when leaf material was originated from the upper soybean trifoliate. The susceptible soybean genotype did not exhibit induced resistance characteristics. Food offered as leaf disc was better at demonstrating induced resistance in previously injured soybean, whereas offering entire leaflet the induced effects were less pronounced. Here we provide new findings on soybean resistance by demonstrating that resistance induction to S. cosmioides herbivory is dependent on the plant genotype and leaf position where injury took place, with negative effects better evinced in bioassays using leaf discs than entire leaflets.     

Acute and Chronic Toxicities of an Annonin-Based Commercial Bioinsecticide and a Joint Mixture with a Limonoid-Based Formulation to the Fall Armyworm

The bioactivity of a newly registered annonin-based formulation (Anosom® 1 EC) was investigated for use against the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), both singly and mixed with a limonoid-based formulation (Azamax® 1.2 EC) using dietary exposure bioassays. Anosom® 1 EC caused significant mortality in S. frugiperda larvae exposed to treated artificial media, with the activity level dependent on both the concentration and the exposure time. In addition to exhibiting acute toxicity, this formulation (tested at LC₅₀) also caused growth inhibition of S. frugiperda, as demonstrated by a significant reduction in pupal weight and viable larval and pupal phases and an increase in the duration of the larval stage. Moreover, the bioinsecticide caused an increase in the proportion of deformed or defective pupae; these were characterized by the retention of exuvia from the last larval instar. The bioinsecticide (at the previously estimated LC₉₀) was, in a time-dependent manner, equally as toxic as the limonoid-based biopesticide (Azamax® 1.2 EC), which was tested at concentrations recommended for the management of S. frugiperda in Brasil. Moreover, the binary mixture (1/2 LC₉₀ of Anosom® 1 EC + 1/2 the recommended rate of Azamax® 1.2 EC) of both bioinsecticides caused a similar level of mortality compared to the bioinsecticides tested individually (full concentration), demonstrating an additive effect of these commercial bioinsecticides. In light of these findings, this standardized formulation based on extract of Annona squamosa can constitute a useful component in the framework of S. frugiperda management, mainly in organic food production systems.     

Attraction of the Larval Parasitoid <Emphasis Type="Italic">Spintherus dubius</Emphasis> (Hymenoptera: Pteromalidae) to Feces Volatiles from the Adult <Emphasis Type="Italic">Apion</Emphasis> Weevil Host

The behavioral response of the larval parasitoid Spintherus dubius (Hymenoptera: Pteromalidae) to volatile compounds derived from its Apion weevil hosts was investigated in two-choice bioassays. Odor source candidates were the larval and adult stages of weevils, clover flowers, and feces from adult weevils. Despite S. dubius being a larval parasitoid, the odor of weevil larvae isolated from the clover flowers was not attractive to female parasitoids. Surprisingly, S. dubius females were instead attracted by the odor from the feces of adult weevils. The female parasitoids were similarly attracted to the feces produced by the two main hosts, the red clover weevil (A. trifolii) and the white clover weevil (A. fulvipes). Chemical analysis of the volatile composition of feces produced by the two hosts revealed qualitatively similar odor profiles, correlating with the observed attraction by the parasitoid towards both odor sources. Some of the identified volatile compounds are commonly present in clover plant headspace fractions and may function as a kairomone to facilitate orientation by S. dubius to Apion-infested clover flowers. Larval and adult weevils were not attractive for parasitoid females, whereas, for the white clover weevil-plant association, infested flowers were highly attractive. These data show the use by the clover weevil parasitoid of an alternative source of olfactory information for locating its host.     

Toxicity and kinetics of spinosad in different developmental stages of the endoparasitoid <Emphasis Type="Italic">Hyposoter didymator</Emphasis> (Hymenoptera: Ichneumonidae) and its host <Emphasis Type="Italic">Spodoptera littoralis</Emphasis> larvae (Lepidoptera: Noctuidae)

The toxicity of spinosad was evaluated using the RaPID Assay^® Spinosad immunosorbent assay in different developmental stages of the parasitoid, Hyposoter didymator, and in its host, fourth-instar larvae of the cotton leafworm Spodoptera littoralis. Spinosad was applied directly to pupae and adults of H. didymator (ingestion or topical application) or to the immature stages of the parasitoid via the host larvae. Low amounts of spinosad were recovered from S. littoralis host larvae after topical treatment, and the compound was mainly retained in the hemolymph. Amounts of spinosad detected in third-instar larvae of H. didymator, pulled out from the hemolymph of parasitized S. littoralis larvae, were 85 pg (3.57 ng a.i./g body weight) in dead larvae, and 82 pg (3.42 ng a.i./g body weight) in alive individuals. After topical treatment of H. didymator cocoons, most of the compound was retained in the silken cocoon, preventing contamination of the pupa. Also in the parasitoid adults, relatively low amounts of spinosad were accumulated in the body overall, but half of all the insecticide recovered was found in the ovaries. The kinetic results obtained help to better understand the toxicity of spinosad in the complex S. littoralis–H. didymator, and to ascertain the compatibility between spinosad and the parasitoid for optimizing the control of lepidopteran pests.     

Parasitism of <Emphasis Type="Italic">Spodoptera litura</Emphasis> (Lepidoptera: Noctuidae) by <Emphasis Type="Italic">Microplitis prodeniae</Emphasis> (Hymenoptera: Braconidae)

Spodoptera litura Fabricius is a major vegetable pest that is widely distributed throughout tropical, subtropical and temperate regions. Microplitis prodeniae Rao and Chandry is a solitary endoparasitoid of S. litura. To assess the potential use of this parasitoid as a biological control agent, the reproductive schedule, fecundity and functional response of M. prodeniae were investigated under conditions of 28 ± 1°C and 70 ± 10% relative humidity with a 14:10-h L:D photoperiod. The parasitoid’s average lifetime fecundity was 171.0 ± 10.4 eggs, of which approximately 50% were laid within the first 3 days. Additionally, M. prodeniae exhibited a Holling type II functional response, and the estimated maximum numbers of the 1st, 2nd and 3rd instar larvae that were parasitized by a single M. prodeniae female were 71.6, 78.4 and 41.5 larvae over a 24-h period, respectively. The results of this study suggest that M. prodeniae has great potential as a candidate for controlling S. litura and can guide efforts in its mass production.     

Dynamics of host plant selection and host-switching by silver-spotted skipper caterpillars

Investigations of host plant selection in herbivorous arthropods have emphasized the importance of oviposition site selection by adults; however, a more complete picture of this process requires additional consideration of the factors influencing host plant choice during the immature feeding stages. We conducted a series of larval choice experiments to examine both the innate and induced preferences of larvae of the Silver-spotted skipper (Epargyreus clarus L.) on three commonly used hosts (Wisteria, Robinia, and Pueraria). Late instar E. clarus larvae reared on each of the three host plants displayed an overall pattern of innate preferences that correlated well with larval performance measures and reflected differences in foliar nutrient concentrations. Larval preferences were also influenced by rearing host species, indicating a role for feeding-induced preferences. When larvae reared on low-quality Wisteria for the first four instars were switched to higher quality Pueraria for the final instar, they developed more quickly and attained significantly higher pupal mass than larvae maintained on Wisteria throughout development. Similarly, larvae switched from Pueraria to Wisteria for the final instar suffered increased development time and produced significantly smaller pupae than those maintained on Pueraria throughout. Thus host-switching, particularly during the more mobile final instars, appears to offer larvae an opportunity to recoup fitness losses associated with early development on a low-quality host. For an equal amount of consumption, larvae feeding on Pueraria gained 50% more mass than those feeding on Wisteria, reflecting measured differences in foliar nitrogen concentration; despite these overall differences in quality, larval growth efficiency was similar among hosts. Especially in the age of common exotic plant introductions, a full understanding of the behavioral component of host selection by herbivorous insects requires appreciation of the dynamic role that immatures can play in host selection and use.     

Effect of excretory-secretory products of some fouling organisms on settling and metamorphosis of the larvae of <Emphasis Type="Italic">Styela rustica</Emphasis> (Ascidiae)

The effect of the excretory-secretory products of some fouling animals on the settling and metamorphosis of larvae of the solitary ascidian Styela rustica was assessed. The substances secreted by the sponge Halichondria panicea stimulated settling of larvae, but concurrently blocked their metamorphosis. The excretory-secretory products of the mussel Mytilus edulis and the ascidian Molgula citrine did not affect settling of the S. rustica larvae but impeded their subsequent development. Water conditioned by the bivalve Hiatella arctica, stimulated settling and, apparently, metamorphosis of the larvae of S. rustica. The chemical substances produced by adult individuals of S. rustica facilitated settling of conspecific larvae but slightly delayed their metamorphosis.     

The Morphology of the Mandibles in Zoea I Larvae of the Burrowing Shrimp Genera <Emphasis Type="Italic">Upogebia</Emphasis> (Gebiidea) and <Emphasis Type="Italic">Nihonotrypaea</Emphasis> (Axiidea)

The mandibles in the first zoeal stage of five species of the burrowing shrimp genera Upogebia (infraorder Gebiidea) and Nihonotrypaea (infraorder Axiidea) have been examined by scanning electron microscopy. The general shape of the mandibles in Upogebia zoeae is similar to that in Anomura larvae; in Nihonotrypaea, it is intermediate between the mandibles of anomuran and caridean shrimp larvae. The asymmetry of the mandibles, which is more pronounced in Nihonotrypaea, is confirmed. Species-specific features of the structure of the incisor process are found in three Upogebia species, while two Nihonotrypaea species almost do not differ in the mandible structure in their zoea I larvae. The morphological features of the mandibles indicate differences in the diet of Upogebia and Nihonotrypaea larvae. Under natural conditions, zoea I of the studied Nihonotrypaea species may feed on diatoms, which should be taken into account when rearing these decapod larvae in the laboratory.     

Parasitism rates and parasitoid complexes of the wheat midges, <Emphasis Type="Italic">Sitodiplosis mosellana</Emphasis>, <Emphasis Type="Italic">Contarinia tritici</Emphasis> and <Emphasis Type="Italic">Haplodiplosis marginata</Emphasis>

Three species of cecidomyiid midges (Diptera: Cecidomyiidae), whose larvae overwinter in the soil, can cause significant yield losses on wheat in Europe: the orange wheat blossom midge, Sitodiplosis mosellana (Géhin), the yellow wheat blossom midge, Contarinia tritici (Kirby), and the saddle gall midge, Haplodiplosis marginata (von Roser). The biological control of wheat midges by their parasitoids can contribute to reduce the midge populations. Soil samples were collected in several fields in Belgium in 2012–2014 in order to characterize the parasitism rates and parasitoid complexes in overwintering larvae. The parasitism rates varied greatly between the sampled fields: 3–100, 0–100 and 2% for S. mosellana, H. marginata and C. tritici, respectively. The parasitism rate was not related to the larval density of wheat midge. The three wheat midges have totally distinct parasitoid complexes in Belgium. Eight species (Hymenoptera: Pteromalidae and Platygastridae) were found as parasitoid of S. mosellana: Macroglenes penetrans (Kirby), Amblypasis tritici (Walker), Euxestonotus error (Fitch), Euxestonutus sp. Fouts, Leptacis sp. Foerster, Platygaster gracilipes (Huggert), Platygaster nisus Walker, and Platygaster tuberosula (Kieffer). According to their abundance, M. penetrans, E. error and P. tuberosula appeared as the main parasitoids of S. mosellana in Belgium. For the two other wheat midges, only one species of the family Platygastridae was found for each midge: Platygaster equestris (Spittler) for H. marginata and Synopeas myles (Walker) for C. tritici.     

Seasonal Abundance and Predatory Potential of <Emphasis Type="Italic">Stethorus aptus</Emphasis> Kapur (Coleoptera: Coccinellidae): A Biocontrol Agent of Tea Red Spider Mite <Emphasis Type="Italic">Oligonychus coffeae</Emphasis> Nietner (Acarina: Tetranychidae)

The tea red spider mite, Oligonychus coffeae Nietner is one of the major pests of tea plants in North-east India. The ladybird beetle, Stethorus aptus Kapur, is a newly reported predator of O. coffeae. Predatory efficiency study of S. aptus under laboratory conditions revealed that adult of S. aptus consumed significantly more mites than larvae. In free choice condition, the predator consumed within a range of 48–56 adults and 82–90 larvae of O. coffeae whereas the 3rd and 4th instar larvae of S. aptus consumed 20–26 adults and 50–60 larvae of O. coffeae per day respectively. Population dynamics of S. aptus was observed for 1 year under field conditions. The maximum density of the predator was recorded during January to March and it gradually declined from September onwards. Population of S. aptus showed positive correlation with its prey O. coffeae and relative humidity while effect of other factors was insignificant.     

Pelagic larval dispersal habits influence the population genetic structure of clam <Emphasis Type="Italic">Gomphina aequilatera</Emphasis> in China

Pelagic larval dispersal habits influence the population genetic structure of marine mollusk organisms via gene flow. The genetic information of the clam Gomphina aequilatera (short larval stage, 10 days) which is ecologically and economically important in the China coast is unknown. To determine the influence of planktonic larval duration on the genetic structure of G. aequilatera. Mitochondrial markers, cytochrome oxidase subunit i (COI) and 12S ribosomal RNA (12S rRNA), were used to investigate the population structure of wild G. aequilatera specimens from four China Sea coastal locations (Zhoushan, Nanji Island, Zhangpu and Beihai). Partial COI (685 bp) and 12S rRNA (350 bp) sequences were determined. High level and significant F_ST values were obtained among the different localities, based on either COI (F_ST?=?0.100–0.444, P?<?0.05) or 12S rRNA (F_ST?=?0.193–0.742, P?<?0.05), indicating a high degree of genetic differentiation among the populations. The pairwise N_m between Beihai and Zhoushan for COI was 0.626 and the other four pairwise N_m values were >?1, indicating extensive gene flow among them. The 12S rRNA showed the same pattern. AMOVA test results for COI and 12S rRNA indicated major genetic variation within the populations: 77.96% within and 22.04% among the populations for COI, 55.73% within and 44.27% among the populations for 12S rRNA. A median-joining network suggested obvious genetic differentiation between the Zhoushan and Beihai populations. This study revealed the extant population genetic structure of G. aequilatera and showed a strong population structure in a species with a short planktonic larval stage.     

Collection and aging of greater amberjack <Emphasis Type="Italic">Seriola dumerili</Emphasis> larvae and juveniles around the Penghu Islands,Taiwan

To investigate the early life history of Seriola dumerili, we first validated otolith daily increments using reared fish (11–51 days after hatching). Four larval and early-juvenile S. dumerili were collected in May and July 2015 around the Penghu Islands, Taiwan (23.45–23.70 °N, 119.40–119.70 °E), by surface larval net towing, but not from drifting seaweeds. Seriola dumerili were caught at the thermal front, and the total lengths and ages ranged 7.4–42.5 mm and 18–56 days, respectively. Our results indicate that the hatching dates of S. dumerili were April to June and larvae may have been accumulated in the frontal zone before the juvenile phase.     

The plant growth promoting bacterium <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> is vertically transmitted in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> (common bean)

Bactrocera dorsalis (Diptera: Tephritidae) is a serious menace to agricultural production worldwide. In order to prevent further damage, it is of paramount important that cost-effective strategies should be developed for their management. Gut bacteria has established diverse relationships with their insect hosts, which could be exploited in pest management programs to improve on control efficiency. In this study, gut bacteria isolates identified by culture dependent technique were incorporated into larval diets in an attempt to understand the roles they play in the development and survival of oriental fruit fly. From our results, the isolated bacteria belonged to four different phyla including the Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria. The response of the fly to different gut isolates varied greatly. Diets enriched with Enterococcus phoeniculicola had lower larval developmental duration, higher pupal weight, and an increased percentage survival. On the other hand, diets supplemented with Lactobacillus lactis had negative effects on B. dorsalis development. This study provides clues on how symbiotic bacteria could be exploited in mass rearing for an efficient implementation of the Sterile Insect Technique (SIT) in pest management programs.