Immunity of an alternative host can be overcome by higher densities of its parasitoids Palmistichus elaeisis and Trichospilus diatraeae

Parasitism and Suitability of Trichogramma chilonis on Large Eggs of Two Factitious Hosts: Samia cynthia ricini and Antheraea pernyi

Trichogramma, an effective biological control agent, demonstrates promise in environmentally sustainable pest management through its parasitic action toward insect eggs. This study evaluates the parasitism fitness and ability of T. chilonis with regard to two factitious host eggs, aiming to develop a cost-effective biological control program. While T. chilonis demonstrated the ability to parasitize both host eggs, the results indicate a preference for ES eggs over COS eggs. The parasitism and emergence rates of T. chilonis regarding ES eggs (parasitism: 89.3%; emergence: 82.6%) surpassed those for COS eggs (parasitism: 74.7%; emergence: 68.8%), with a notable increase in the number of emergence holes observed in the ES eggs compared to the COS eggs. Moreover, the developmental time of T. chilonis for ES eggs (10.8 days) was shorter than that for COS eggs (12.5 days), resulting in a lower number of dead wasps produced. Notably, no significant difference was observed in the female ratios between the two species. A comprehensive analysis was conducted, comparing the size and shell thickness of the two factitious hosts. The ES eggs exhibited smaller dimensions (length: 1721.5 μm; width: 1178.9 μm) in comparison to the COS eggs (length: 2908.8 μm; width: 2574.4 μm), with the ES eggshells being thinner (33.8 μm) compared to the COS eggshells (47.3 μm). The different host species had an effect on the body length of the reared parasitoids, with T. chilonis reared on COS hosts exhibiting a larger body length (female: 626.9 µm; male: 556.7 µm) than those reared on ES hosts (female: 578.8 µm; male: 438.4 µm). Conclusively, the results indicate that ES eggs present a viable alternative to COS eggs for the mass production of Trichogramma species in biological control programs.

Selectivity of Insecticides to a Pupal Parasitoid, Trichospilus diatraeae (Hymenoptera: Eulophidae), of Soybean Caterpillars

Selectivity is an important aspect of modern insecticides to be able to target pests whilst maintaining beneficial entomofauna in the crop. The present objective was to assess the selectivity of different insecticides for the pupal parasitoid of soybean caterpillars, i.e., Trichospilus diatraeae Cherian & Margabandhu, 1942 (Hymenoptera: Eulophidae). Acephate, azadirachtin, Bacillus thuringiensis (Bt), deltamethrin, lufenuron, teflubenzuron and thiamethoxam + lambda-cyhalothrin at the highest recommended concentrations for the soybean looper Chrysodeixis includens (Walker, [1858]) (Lepidoptera: Noctuidae), as well as water in the control, were used against the pupal parasitoid T. diatraeae. The insecticides and the control were sprayed on the soybean leaves, which were left to dry naturally and placed in cages with T. diatraeae females in each one. Survival data were submitted to analysis of variance (ANOVA) and the means were compared using Tukey's HSD test (α = 0.05). Survival curves were plotted according to the Kaplan-Meier method, and the pairs of curves were compared using the log-rank test at 5% probability. The insecticides azadirachtin, Bt, lufenuron and teflubenzuron did not affect T. diatraeae survival, while deltamethrin and thiamethoxam + lambda-cyhalothrin presented low toxicity and acephate was highly toxic, causing 100% mortality in the parasitoid. Azadirachtin, Bt, lufenuron and teflubenzuron are selective for T. diatraeae and could be used in IPM programs.

Optimal clutch size for quality control of bisexual and Wolbachia-infected thelytokous lines of Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) mass reared on eggs of a substitutive host, Antheraea pernyi Guérin-Méneville (Lepidoptera: Saturniidae)

BACKGROUND

Trichogramma dendrolimi has been widely used in augmentative biocontrol of lepidopteran pests in China. In mass production of T. dendrolimi using Antheraea pernyi eggs as substitutive hosts, which are large in size, as clutch size is a parameter of importance to produce high quality parasitoids. Here, we aimed to determine the optimal clutch size for the bisexual Wolbachia-uninfected line (TdB) and Wolbachia-infected thelytokous line (TdT) of T. dendrolimi reared on A. pernyi eggs.

RESULTS

A medium clutch size of 42.75 to 62.27 for TdB and 52.93 to 57.14 for TdT was optimal to maximize fitness-correlated traits of parasitoid individual. The optimal clutch sizes with maximized parameters included adult emergence rate, adult body size, adult longevity, fecundity, and sum of fecundity of all females per brood were 58.31 (86.00%), 42.75 (231.11 μm), 50.92 (2.69 days), 62.27 (150.89 eggs), and 83.25 (7926.33 eggs) for TdB and 57.14 (94.54%), 52.93 (236.97 μm), 53.64 (2.62 days), 56.80 (161.01 eggs), and 70.10 (8579.71 eggs) for TdT. The TdT had a shorter adult longevity, longer development time, and higher adult emergence rate than did its non-infected bisexual counterpart.

CONCLUSION

A medium brood size in a A. pernyi egg host was optimal to produce offspring parasitoids with higher fitness parameters for both bisexual Wolbachia-uninfected and thelytokous Wolbachia-infected lines of T. dendrolimi. The determination of optimal clutch size for T. dendrolimi will provide the reference for the quality control of T. dendrolimi production and improvement of the field performance of the wasps. © 2020 Society of Chemical Industry.

Tetrastichus howardi (Hymenoptera: Eulophidae): first report of parasitism in Oxydia vesulia (Lepidoptera: Geometridae)

The adaptation of native lepidopteran species to eucalyptus plantations reduces the productivity of this crop in Brazil. Oxydia vesulia Cramer (Lepidoptera: Geometridae) is a secondary pest, frequently reported in eucalyptus plantations with population outbreaks and economic damages. Methods of biological control of this pest may include the use of the exotic pupae endoparasitoid Tetrastichus howardi Olliff (Hymenoptera: Eulophidae), reported as efficient to controlling lepidopteran pests. The parasitism of O. vesulia caterpillars and pupae by T. howardi was evaluated under controlled conditions (25 ± 1 ºC, 60 ± 20% humidity and 12:12 h L:D). Each O. vesulia caterpillar or pupae was individually placed in a flat-bottom tube with 10 and 15 females of T. howardi for 48h, respectively. The parasitoids were removed after that period, the caterpillars were fed and the pupae were maintained until emergence of the parasitoid or formation of pupae and emergence of adults of this pest. The fourth-instar caterpillars of O. vesulia, after the parasitism period, were kept in pots with Eucalyptus urophylla leaves, changed daily until the end of the experiment. A total of 40% of the caterpillars died before the pre-pupae stage, 40% reached the pupae stage and died due to inadequate adult formation and 20% generated moths, but none adult parasitoid emerged from the caterpillars. All pupae of O. vesulia were parasitized and showed emergence of parasitoids. The parasitism of O. vesulia caterpillars and pupae by T. howardi shows the potential of this natural enemy for the integrated management of this defoliator pest in eucalyptus plantations.

Tetrastischus howardi density and dispersal toward augmentation biological control of sugarcane borer

The number of Tetrastischus howardi (Olliff) females to be released and their dispersion should be known, that way, used D. saccharalis pupae as sentinel host to measure parasitism as function of the release density of the parasitoid and its location in the field. Two sets of trials were run aiming first to define the number of parasitoids to be released and the dispersal of the parasitoid using plots in sugarcane commercial fields, respectively. Pieces of sugarcane stalk holding sentinel pupae were taken to the field and exposed to parasitism in both trials. The parasitoid was released at the rate of 20, 40, 80, and 160 females per sentinel pupa, except for the control plot without releasing. The parasitism rate was calculated based on the recovered pupae after 96 h of exposure time from releasing the parasitoids. The models estimated the best parasitism rate by releasing 102 parasitoids per pupa. In the second trial, sentinel pupae were arranged in five subsequent circles corresponding 4, 8, 12, 16, and 20 m around the central parasitoid releasing point at rate of 4, 8, 12, 16, and 18 pupae per circle. The mean estimated dispersal distance was 7.64 m, with a covering area of 80.07 m². Based on these findings, release of T. howardi is recommended in 125 points per hectare of sugarcane at rate of 102 females per pupa of the pest aiming to achieve homogeneous distribution and parasitism.

Do parasitoid density and host age affect the parasitism of Palmistichus elaeisis (Hymenoptera: Eulophidae)?

ABSTRACT: The incidence of lepidopteran defoliants is one of the environmental factors that regulate the productivity of cultivated forests. The parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae) has significant importance for its efficiency in the parasitism of pupae of these Lepidoptera. The objective of this study was to evaluate the development and reproduction of P. elaeisis in different densities of pupae of Spodoptera frugiperda (Lepidoptera: Noctuidae) at different ages. Pupae of 24, 48, 72 and 96 hours were exposed at densities of 1:1, 4:1, 10:1, 19:1, 31:1 and 46:1 parasitoids/host, respectively. The parasitoids remained in contact with the pupae for 72 hours in 500 mL plastic pots, conditioned in an air-conditioned room, with temperature of 25 ± 2°C, relative humidity of 70 ± 10% and photoperiod of 12 hours. It was concluded that the density of 10:1 presented great results of parasitism, and further increase of density was not needed. Pupae of 24 and 48 hours had a higher percentage of emergence. Biological variables were affected neither by parasitoid densities nor by host age.

Trichospilus diatraeae (Hymenoptera: Eulophidae): development and reproduction in Lepidoptera palm oil pests

Brazil is a leading palm oil producer, but the defoliating caterpillars Opsiphanes invirae Hübner Brassolis sophorae L. (Lepidoptera: Nymphalidae) can reduce the productivity of this crop. The aim of this study was to evaluate the development and reproduction of the parasitoid Trichospilus diatraeae Cherian & Margabandhu (Hymenoptera: Eulophidae) in pupae of these oil palm defoliators. Ten O. invirae or B. sophorae pupae with up to two days old were exposed each to 30 T. diatraeae females for 48 hours. Parasitism and emergence of the progeny of T. diatraeae were similar in pupae of both Lepidoptera defoliators. The life cycle of this parasitoid was shorter in O. invirae (21.50 ± 0.42 days) pupae than with those of B. sophorae (27.60 ± 1.80 days). The number of the progeny (669.00 ± 89.62) and dead immature (217.13 ± 58.18) of T. diatraeae were higher in B. sophorae pupae than in those of O. invirae with 447.83 ± 51.52 and 13.50 ± 5.23, respectively. The sex ratio and female and male longevity of T. diatraeae emerged from these hosts were similar. The reproductive traits, especially the number of individuals (offspring) of T. diatraeae were better with B. sophorae pupae than with those of O. invirae.

Hemolectin expression reveals functional heterogeneity in honey bee (Apis mellifera) hemocytes

The identification of molecular markers considerably facilitated the classification and functional analysis of blood cell types. Apis mellifera hemocytes have been classified by morphological criteria and lectin binding properties; however, the use of molecular markers has been minimal. Here we describe a monoclonal antibody to a non-phagocytic subpopulation of A. mellifera hemocytes and to a constituent of the hemolymph clot. We demonstrate that the antibody identifies the A. mellifera hemolectin, a protein carrying human von Willebrand factor homology domains, characteristic of proteins involved in blood coagulation and platelet aggregation in mammals. Hemolectin expressing A. mellifera hemocytes contain the protein as cytoplasmic granules and contribute to the formation of a protein matrix, building up around foreign particles. Consequently, hemolectin as a marker molecule reveals a clear functional heterogeneity of hemocytes, allowing for the analytical separation of hemocyte classes, and could promote the molecular identification of hemocyte lineages in A. mellifera.

Superparasitism, immune response and optimum progeny yield in the gregarious parasitoid Palmistichus elaeisis

BACKGROUND

The subsequent deposition of an egg clutch by a female parasitoid into a host already parasitised either by itself or a conspecific (i.e. superparasitism) is a counterintuitive adaptive strategy, particularly considering the female parasitoid's ability to recognise the parasitised hosts. Such a scenario suggests that the adaptive value of superparasitism depends on the number of clutches laid in the same host, with consequences for parasitoid progeny yield. Here, we tested whether such is the case for the gregarious parasitoid Palmistichus elaeisis and explored its underlying basis.

RESULTS

Allowing female parasitoids to lay multiple egg clutches in a single melonworm host pupa, parasitoid progeny and fitness exhibited a peak or optimum at three egg clutches laid per host pupa. In addition, haemocyte count, encapsulation and melanisation decreased with the number of egg clutches laid per host pupa.

DISCUSSION

An optimum number of three clutches laid per host pupa was detected for P. elaeisis. As immune response via haemocyte production, encapsulation and melanisation decreased with the number of clutches laid per host, the higher parasitoid yield and fitness observed is the likely consequence of a compromised immune response coupled with an accommodative (i.e. scramble) larval competitive strategy allowing enough resources for optimum balance of parasitoid number and quality produced. © 2017 Society of Chemical Industry.

A dieta alimentar da presa Tenebrio molitor (Coleoptera: Tenebrionidae) pode afetar o desenvolvimento do predador Podisus nigrispinus (Heteroptera: Pentatomidae)?

Inimigos naturais são importantes para o controle de pragas em culturas agrícolas e florestais. A criação de insetos predadores em biofábricas deve ser de baixo custo para serem utilizados em programas de Manejo Integrado de Pragas (MIP). O objetivo deste trabalho foi avaliar o desenvolvimento de Podisus nigrispinus Dallas, 1851 (Heteroptera: Pentatomidae), alimentado com larvas de Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae), criadas com as seguintes dietas: farelo de trigo, ração triturada ou peletizada para aves poedeiras e fubá de milho. Foram obtidos os parâmetros de desenvolvimento e reprodução necessários para calcular a tabela de vida do predador. Os parâmetros da tabela de vida revelaram crescimento populacional em todos os tratamentos. No entanto, a taxa líquida de reprodução (Ro) de P. nigrispinus foi menor quando alimentados com larvas de T. molitor criadas com fubá de milho, mostrando ser a alimentação menos adequada para esse predador. Por proporcionar maior número total de ovos, o farelo de trigo constituiu a melhor dieta para P. nigrispinus. Estudos sobre dietas de presas alternativas são importantes, pois podem favorecer a nutrição de inimigos naturais e, consequentemente, melhorar o desempenho das criações massais em laboratório.

Insights into the Melipona scutellaris (Hymenoptera, Apidae, Meliponini) fat body transcriptome

The insect fat body is a multifunctional organ analogous to the vertebrate liver. The fat body is involved in the metabolism of juvenile hormone, regulation of environmental stress, production of immunity regulator-like proteins in cells and protein storage. However, very little is known about the molecular mechanisms involved in fat body physiology in stingless bees. In this study, we analyzed the transcriptome of the fat body from the stingless bee Melipona scutellaris. In silico analysis of a set of cDNA library sequences yielded 1728 expressed sequence tags (ESTs) and 997 high-quality sequences that were assembled into 29 contigs and 117 singlets. The BLAST X tool showed that 86% of the ESTs shared similarity with Apis mellifera (honeybee) genes. The M. scutellaris fat body ESTs encoded proteins with roles in numerous physiological processes, including anti-oxidation, phosphorylation, metabolism, detoxification, transmembrane transport, intracellular transport, cell proliferation, protein hydrolysis and protein synthesis. This is the first report to describe a transcriptomic analysis of specific organs of M. scutellaris. Our findings provide new insights into the physiological role of the fat body in stingless bees.

Oogenesis pattern and type of ovariole of the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

The knowledge on ovigeny in parasitoids is important for basic studies on physiology and applied biological control. The ovigeny pattern and type of ovariole of the parasitoid Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) were studied in newly-emerged females at seven, 14, 24 and 48 h intervals after their emergence from Tenebrio molitor L. pupae (Coleoptera: Tenebrionidae). Females of P. elaeisis presented ovaries composed by four ovarioles of the meroistic polytrophic type. The yolk accumulation and chorionogenesis in P. elaeisis were concluded 24 h after the female emergence. The 48 h-old females show a high quantity of egg ready for oviposition. These findings can help to improve the mass production of P. elaeisis and the augmentative biological control by using this natural enemy.

Densidade de fêmeas de Palmistichus elaeisis Delvare & LaSalle, 1993 (Hymenoptera: Eulophidae) para sua reprodução em pupas de Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae)

A densidade de parasitoides por hospedeiro influencia nas suas principais características biológicas. Assim, o objetivo desse trabalho foi avaliar o desenvolvimento do parasitoide Palmistichus elaeisis Delvare & LaSalle, 1993 (Hymenoptera: Eulophidae) em pupas de Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae) expostas nas densidades de 1:1, 2:1, 4:1, 6:1, 8:1, 10:1 ou 12:1 parasitoides/hospedeiro, respectivamente. Os parasitoides permaneceram em contato com as pupas por 24 horas em tubos de vidro (14,0 x 2,2 cm), acondicionadas em câmara climatizada a 25 ± 1º C, 70 ± 10% de UR e fotofase de 14 horas. Observou-se 54,54 e 90,90% de pupas parasitadas nas densidades de 1:1 e 2:1, respectivamente, e 100,00% nas demais densidades com melhor índice de emergência (72,72%) na densidade 6:1. A duração do ciclo de vida (ovo-adulto) decresceu com o aumento da densidade de fêmeas e variou de 20 a 22 dias. A progênie variou de 16 a 225 descendentes por pupa, com melhor resultado na densidade 8:1. A razão sexual do parasitoide variou de 0,95 ± 0,00 a 0,97 ± 0,01, sem diferença significativa e o comprimento do corpo de fêmeas e de machos variou de 1,95 ± 0,02 a 2,22 ± 0,03 mm e de 1,49 ± 0,02 a 1,87 ± 0,01 mm, respectivamente. Seis a oito fêmeas de P. elaeisis por pupa de A. gemmatalis proporcionam maior emergência e progênie do parasitoide, viabilizando sua criação massal.