Entomologia Experimentalis et Applicata最新文献

The host immunosuppression by parasitic wasps is an important component of the host regulation strategy. The venom injected at the oviposition is one of the key-factors involved in this host alteration and, in some parasitoids, its immunosuppressive role is complemented by wasp's symbionts. Most studies in this research area are related to hosts belonging to Lepidoptera and Diptera, for which a strong immune response is observed, whereas little is known for hemimetabolous host species, characterized by apparently much weaker defense barriers. To fill this research gap, here we focus on the host–parasitoid system Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) – Aphidius ervi Haliday (Hymenoptera: Braconidae). We functionally characterized a serine protease homolog (AeSPH) protein in vivo, identified in the venom of the aphid endoparasitoid A. ervi, generating AeSPH-depleted female wasps by RNA interference and evaluating their capacity to successfully parasitize the host. Parasitism success rate was negatively affected by AeSPH knockdown and associated with an increased phenoloxidase (PO) cascade activation in aphids, scored by measuring PO enzymatic activity and the expression of phenoloxidase activating factor 2, a proPO-activating gene upregulated in response to A. ervi parasitism. Our results indicate that AeSPH contributes to parasitism success by inhibiting the melanization response of the host, which is therefore an important component of the defense barriers involved in the parasitoid egg suppression. The ongoing studies on other virulence factors in A. ervi venom will allow to further characterize the immunosuppression strategy and its possible broader role in the host regulation through its action on aphid symbiont development.

The tussock moth, Orgyia trigotephras Boisduval (Lepidoptera: Erebidae), is one of the main emerging pests of kermes oak, Quercus coccifera L. (Fagaceae), in the Mediterranean area, where it can cause the defoliation of several hectares of forests during its population outbreaks. Despite this, no specific sampling procedures to properly estimate the population density of this pest have been developed yet. The aims of this research were to develop and compare enumerative and binomial sequential sampling plans to estimate the population density of O. trigotephras in forest environments. Data were collected in four forest stands dominated by Q. coccifera in Tunisia for 7 years (from 2013 to 2019) to take into consideration the potential spatio-temporal variability in pest density. Plant community composition was determined at the beginning of the experimental trials, and enumerative and binomial sampling plans were developed at precision levels of 0.15 and 0.25. Over the entire sampling period, the average O. trigotephras egg batch density differed significantly among sites. Sample sizes of enumerative sampling plans were approximately 39 and 109 trees to estimate an average density of 0.50 O. trigotephras egg batches per tree at the precision levels of 0.25 and 0.15, respectively. Instead, binomial sequential sampling plans required smaller sampling sizes than the enumerative sampling plan. Our findings represent the baseline to develop a program for monitoring O. trigotephras at a large spatial scale.

Insects are intentionally introduced to various regions out of their native ranges to perform fundamental functions, such as pest control, and some keep dispersing from introduction sites to become cosmopolitan and even invasive. The African horned dung beetle, Euoniticellus intermedius (Reiche) (Coleoptera: Scarabaeidae), has been intentionally introduced on multiple continents to bury cattle dung and control livestock pests, but has naturally dispersed and became very abundant at various latitudes and elevations out of its native and original introduction ranges. This beetle has been considered invasive, but there is no direct evidence of its effects on displacing native species. As it is highly fecund, E. intermedius has been an important model in experimental studies performed in nature and in the laboratory in multiple fields. In evolutionary biology, it serves as a model for sexual selection, given the sexual dimorphism characterized by the presence of a horn in males which is correlated with individual condition and strength, and which is absent in females. In ecotoxicology, it has been studied regarding physiological mechanisms of responses to contaminants, population declines, and evolutionary responses to challenging toxic conditions. Given its importance in burying dung in cattle pastures, experiments have also determined environmental conditions that limit this ecological function. Despite being unique in its tolerance to a wide variety of stressors and environments, this species is sensitive to current conditions of global change, including warming and pollution. We identify the most promising questions to be solved in physiology, ecology, and evolution, for which E. intermedius would be an ideal study system.

The sterile insect technique (SIT) is used for the management of tephritid fruit fly pests. The South American fruit fly, Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae), is one potential pest to be targeted by means of SIT. The success of SIT depends, to a large extent, on the sexual performance of sterile males. Various approaches have been evaluated with the aim of improving their sexual performance. These include the exposure to plant-derived compounds and/or the provision of protein sources in the adults' diet capable of stimulating male mating success. The present study aimed to determine whether exposure to volatiles of Citrus limon (L.) Burm. F. (Rutaceae) essential oil and limonene confers a mating advantage to A. fraterculus laboratory males fed two distinct dietary regimes when competing with wild males for wild females under field cage conditions. Dietary regimes were, one, with non-hydrolysed brewer's yeast and sugar (1:3 ratio), and the other with brewer's yeast hydrolysate enzymatic and sugar (1:12 ratio). The effect was evaluated in four variables associated with mating success: number of copulas obtained, latency to mate, copula duration, and copula location. Exposure to volatiles did not affect the number of matings achieved, irrespective of the diet given to the males. When laboratory males were fed with brewer's yeast hydrolysate, the effect of volatile exposure was shown in latency to mate, copula duration, and copula location. When the laboratory males were fed with non-hydrolysed brewer's yeast, the effect of volatile exposure was shown only in copula duration. Laboratory males fed brewer's yeast hydrolysate achieved the same number of matings as wild males, whereas laboratory males fed non-hydrolysed brewer's yeast had lower performance.

The cotton boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is one of the most important insect pests of cotton, causing significant yield losses. This insect completes its life cycle only on the flower structures of some Malvaceae species, with cotton being its preferred host. However, during the cotton off-season, the boll weevil enters a reproductive dormancy state, in tropical regions, with important alterations in their reproduction organs. During this period, a remaining insect population survives feeding on a variety of other food sources, but the insects do not reproduce. We hypothesized that these alterations in the insect's reproductive organs are associated with the nutritional levels provided by alternative food sources during the cotton off-season. To test our hypothesis, we first investigated food sources that sustain insect survival for long periods, such as weed species and fruits of cultivated crops. Then, we evaluated how various food sources affect the reproductive organs and reproductive capacity of the boll weevil. Among the alternative food sources tested, insect longevity was highest on banana (Musa paradisiaca L.), mango (Mangifera indica L.), papaya (Carica papaya L.), milkweed (Euphorbia heterophylla L.), and lilac tasselflower (Emilia sonchifolia L.). However, only banana and mango resulted in greater longevity than cotton squares. Banana was the preferred food and resulted in the highest levels of nutrients in the insects. Additionally, insects previously fed on banana made more oviposition punctures on cotton squares than those fed only on cotton squares, which resulted in a significantly higher number of emerged adults. Histological analysis of the insects' reproductive organs showed that feeding on papaya resulted in morphological changes and testicle degradation. In conclusion, we present evidence that boll weevils fed on alternative food sources (other than cotton squares or similar-quality food) display a nutritional imbalance, associated with substantial alterations in the reproductive tissues of this insect, which may trigger the reproductive dormancy state.

The extent of regeneration is impacted by the stage of amputation in ladybird beetles: a case study in Cheilomenes sexmaculata – H. Alam, S. Rai, P.C. Verma & G. Mishra (https://doi.org/10.1111/eea.13423).

Soybean, Glycine max (L.) Merr. (Fabaceae), is one of the most important crops worldwide, but caterpillars of various species (Lepidoptera) may greatly reduce its annual yield. Nowadays, the main method of controlling these pest species is based on the use of broad-spectrum insecticides, which are harmful to human health and increase environmental contamination. Therefore, other sustainable methods of control, such as biological control, are in increasing demand. The present study aimed to identify the egg parasitoid species that attack lepidopterans defoliating soybeans in South America's subtropical regions, as well as evaluate their effectiveness at various stages of soybean development. The research was conducted in a commercial soybean field (80 ha) located in Tucumán, Argentina, which was surrounded by wild vegetation as a way to promote biological control. Every week, throughout three consecutive soybean seasons, 20 soybean plants were randomly selected and brought to the laboratory in search of lepidopteran eggs. Over the course of the three crop seasons, the soybean plants were attacked by Anticarsia gemmatalis Hübner (Erebidae), Rachiplusia nu (Guenée), and Chrysodeixis includens (Walker) (both Noctuidae). Six egg parasitoid species were identified, but only three of them were frequently found during the current study. Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) was the most predominant species attacking all lepidopteran pests across all soybean phenological stages. Encarsia porteri (Mercet) (Hymenoptera: Aphelinidae) preferred to attack R. nu eggs, whereas Telenomus cyamophylax Polaszek (Hymenoptera: Scelionidae) parasitized only A. gemmatalis and R. nu eggs. Despite the use of insecticides in the soybean field, the parasitism rates recorded were high. This suggests that using conservation tactics such as native vegetation patches and surrounding alternative crops may result in higher rates of natural control.

Symbionts form intricate associations with their hosts. They can only establish when potential hosts are present, but in addition, their distribution is often influenced by microhabitat preferences, which may not overlap those of their hosts. This leads to a patchy local distribution of the symbiont, being present with some hosts and absent with others. We studied this effect of microhabitat preferences on symbiont distribution by examining the occurrence and density of the obligately ant-associated springtail Cyphoderus albinus Nicolet (Collembola: Paronellidae) across a mosaic of ant nests. Nest structure strongly varied both within and between ant species and included sand, dead wood, arboreal and thatch mound nests. We hypothesized that the symbiotic springtail would show the strongest preference for thermoregulated and organic-rich nests such as thatch mounds. The springtail was found in all thatch mound nests of red wood ants and in all arboreal nests of Lasius fuliginosus (Latreille). A high occurrence (75%) was recorded in the smaller thatch nests of Formica sanguinea Latreille. Lasius, Myrmica and Formica species exhibited variation in nest structures on the ground, establishing nests in both sand and wood. For each of these three host taxa, encountering the springtail was more likely in their wood nests (medium-to-high occurrence), than in their sand nests where the occurrence was low. Nest structure did not only impact springtail occurrence, but their densities as well. The densities within thatch nests were much higher than those in other nest types, achieving the highest densities (1148 individuals per litre of nest material) observed for a social insect symbiont. Our findings emphasize that host nests with wood structures and thatch material provide a more favourable habitat for the springtail compared with soil nests. Overall, this study underscores the role of microhabitat variation in the spatial distribution and density of a symbiotic species.

The ability to estimate the risk of pest infestation can help farmers to reduce pesticide application and provide guidance that would result in better management decisions. This study tested whether different combinations of spatial and temporal risk factors may be used to predict the damage potential of pea moth, Cydia nigricana Fabricius (Lepidoptera: Tortricidae), a major pest in field pea (Pisum sativum L., Fabaceae). Over four consecutive years, the abundance of pea moth was monitored by placing pheromone traps at various field pea-cultivation sites. We also assessed the phenological development stages and the percentage of damaged seeds per 100 pods collected from each growing pea field in a region of approximately 30 km in diameter. The study found the significant infestation risk indicators to be the time of flowering, the date on which male pea moths are first detected in the monitoring traps and the minimum distance to pea fields that were planted and harvested in the previous growing season. The combination of all three factors using a general additive model approach yielded the best results. The model proposed by this study accurately discriminated between low-infestation and high-infestation fields in 95% of cases.

Batocera horsfieldi (Hope) (Coleoptera: Cerambycidae) is an important pole borer pest. It causes serious harm to various hosts, particularly Juglans regia L. (Juglandaceae). In this study, headspace solid-phase microextraction (HS-SPME), gas chromatography–mass spectrometry (GC–MS), and electroantennogram (EAG) responses were combined to examine the mechanism by which B. horsfieldi adults locate their host, J. regia. The results showed that J. regia contained 65 volatile compounds in all, with 36 and 42 volatile substances in bark and leaves, respectively. Moreover, terpenes accounted for the largest relative content among the volatile compounds of bark and leaves, 43.4 and 78.9%, respectively. Ten of 19 selected volatile components elicited significant EAG responses in adult B. horsfieldi, which indicated that the pest may prefer certain volatile compounds when selecting a host. Sex and volatile concentration affected the responses of B. horsfieldi. Male adults had the strongest EAG responses to 1-octen-3-ol, whereas female adults had the strongest EAG responses to linalool. Host selection in B. horsfieldi was somewhat positively associated with the concentrations of the effective volatile compounds in the host. Furthermore, B. horsfieldi showed varying preferences for isomers. This work provided data support for the development of insect attractants, and laid a theoretical foundation for the ecological protection of local forestry.