Search Results (29)

Mating and feeding behavioural differences have been observed between male and female wasps (Hymenoptera: Aculeata). It is hypothesised that these behavioural differences are supported by morphological dimorphisms in their sensory systems. Here, this hypothesis was tested in the parasitoid aculeate wasp Scolia hirta (Scoliidae), which attacks beetle larvae located in the soil. We have found evidence of a link between the main stimuli used by the sexes to access their target resources and the morphology of the sensory system. Males have a more developed visual system with enlarged eyes, ocelli and a higher number of ommatidia, sinc they have to visually locate and chase females immediately after they emerge. Males possess nine types of sensilla (primarily hygrothermo- and mechanoreceptors), and females possess seven types of sensilla, primarily olfactory. In females, the sensilla placoidea occur in greater numbers and are larger in size, in line with their underground host-seeking behaviour. Furthermore, the females had a blunt tip on their distal flagellomere and wider fore tibiae, which suggests that they may use vibrational sounding to detect concealed hosts, similarly to what has been described for some non-aculeate parasitoid wasps. Full article

Postharvest losses from potato tuber moth severely constrain seed quality in Andean smallholder systems. This study evaluated four locally available repellent plants—Ambrosia peruviana, Eucalyptus globulus, Artemisia absinthium, and Minthostachys mollis—applied as dried leaves layered within seed bags of INIA 302 ‘Amarilis’ under farmer-like storage at two highland sites in Cajamarca, Peru (Huaytorco, 3350 m; Samaday, 2750 m), over 187 days. Within each site, a Completely Randomized Design with three bag-level replicates per treatment was used, and damage was assessed after 187 days as incidence of attacked tubers, internal damage severity and live larval counts. Endpoint data were analyzed separately by site using Kruskal–Wallis tests followed by Dunn’s post hoc test with Šidák correction (α = 0.05). Across both sites, all botanicals significantly reduced damage severity and live larval counts relative to the untreated control. At the warmer, lower site, A. absinthium and M. verticillata achieved large effect sizes, with severity and larval numbers reduced by roughly 80–90% compared with the control, while at the cooler, higher site, larvae were not detected in any botanical treatment. These findings indicate that simple layering of dried leaves from locally available plants, particularly wormwood and muña, can substantially mitigate S. tangolias damage in highland seed potato stores and represents a promising, low-cost complement to integrated pest management, although multi-season and dose-response studies are still needed to confirm and refine this approach. Full article

We describe the trophic relationships of tachinid parasitoid flies that attack exophagous, leaf-eating Lepidoptera caterpillars in Área de Conservación Guanacaste (ACG), northwestern Costa Rica over approximately forty years beginning in 1984. The dataset contains more than 34,000 individual tachinid rearings from individual wild-caught caterpillars. Identification of parasitoids and caterpillars up until 2004 was based entirely on morphology. From 2004 onwards most reared specimens were DNA-barcoded and some retroactive barcoding was also carried out with varying degrees of success. Generally, for older specimens, generating good quality-barcodes requires more expensive protocols. Barcoding of reared specimens led to the recognition that many morpho-species were made up of multiple species of flies but those reared from an individual caterpillar were 99.95% a single species. Consequently, estimates of diet breadth of caterpillars and tachinids changed considerably after 2003. The data analysed here were pruned to include only rearings with complete host and food plant data and excluded potentially duplicated rearings and ones whose identification could not be confidently assigned. The cleaned dataset includes 13,735 independent rearings. Chao1 estimates of numbers of tachinid, caterpillar and food plant species suggest that species sampling is 86, 70 and 91 percent complete, respectively. However, this was not the case for bi- and tritrophic interactions which increased linearly with effort. We show that while the tachinids of ACG are more host-specialised than was expected prior to the combined efforts of rearing and barcoding, they have broader host ranges and higher host Shannon diversity indices than either Braconidae or Ichneumonidae. This may be attributable to the effects of the induced host-derived sac enclosing the larvae and their posterior spiracles. Full article

This study investigated the impact of sublethal concentrations of dinotefuran on the predatory behavior and detoxification enzyme activity of Harmonia axyridis, aiming to establish a theoretical foundation for the conservation and utilization of natural enemies and the effective management of wheat aphids. This study treated wheat aphids with sublethal concentrations (LC₂₀ and LC₃₀) of dinotefuran via the leaf dipping method and subsequently used them as prey for the fourth-instar larvae of H. axyridis. The predation amount, instantaneous attack rate, handling time, daily maximum predation amount, and detoxification enzyme activity of H. axyridis were statistically analyzed. The results indicated that the predation of H. axyridis on wheat aphids conformed to the Holling II disc equation. Moreover, in comparison to the control group, the handling time of H. axyridis on wheat aphids was extended, and at the same time, the instantaneous attack rate, maximum daily predation amount, and predation efficiency were all diminished. After the ingestion of LC₂₀- and LC₃₀-dinotefuran-treated aphids, the carboxylesterase levels in H. axyridis were not significantly different from the control, with levels 0.97-fold and 0.94-fold that of the control, respectively. Glutathione-S-transferase (GST) demonstrated an induction impact compared to the control, reaching 1.96- and 1.47-fold higher than the control, respectively. The activity of mixed-functional oxidase (MFO) demonstrated an induction effect compared to the control, measuring 1.98- and 3.04-fold higher than that of the control, respectively. Consequently, the predation function and detoxification enzyme activity of H. axyridis were influenced when consuming wheat aphids treated with sublethal concentrations of dinotefuran, with significant variations across different concentrations, potentially reflecting the survival strategy of insects under dinotefuran stress. Full article

Corn is one of the world’s most economically important cereal crops and can be attacked by Sitophilus zeamais. The control of S. zeamais is mostly based on synthetic insecticides; however, populations of this insect have developed resistance to various chemical compounds. New rational insecticides that prevent the development of resistant populations need to be continuously evaluated. This research aimed to assess the effects mediated by azadirachtin on S. zeamais populations in terms of mortality, survival, food preference, and repellency. Azadirachtin is toxic to S. zeamais at the larval (LC₅₀ = 3.36 ppm), pupal (LC₅₀ = 23.0 ppm), and adult (LC₅₀ = 37.7 ppm) stages. At all stages of insect development, the survival rate was 99.9% in insects not treated with azadirachtin, decreasing to 29.9%, 44.9%, and 68.5% in larvae, pupae, and adults treated with the LC₅₀ of the bioinsecticide, respectively. The preference for untreated corn grains was higher with the LC₂₅ and LC₅₀ of azadirachtin, while the LC₉₅ (209 ppm) repelled adults. Azadirachtin causes lethality in S. zeamais, compromising its survival and reducing the feeding preference on grains protected with repellent activity at high concentrations. Therefore, the use of this bioinsecticide may offer an alternative to control S. zeamais in the field and post-harvest. Full article

Coccinella septempunctata (Linnaeus, 1758) is a voracious predator all over the world where aphids have found a niche. Behavioral studies of C. septempunctata are very important to make them effective bio-controllers. Therefore, this study explains the functional response of C. septempunctata praying on two distinct aphid species, examined in this work at two different temperatures. Six different prey densities (4, 8, 16, 32, 64, and 128 aphids) and two different temperatures (15 and 25 °C) were used in the experiment. All of the development stages of the predator were used to perform the experiment. Every experiment was replicated five times. The type and parameters of functional response were ascertained by the application of Roger’s random predator models and logistic regression. Results showed that C. septempunctata adults and larvae both had a type II functional reaction against the tested aphids in both temperatures. When comparing the fourth instar to other predatory stages, the attack rate against both aphids was shown to be greater. As the temperature rose, so did the attack rate. Fourth instar larvae exhibited attack rates of 1.314 h⁻¹ on Aphis nerii Fonscolombe, 1758 (Hemiptera: Aphididae) and 1.959 h⁻¹ on Lipaphis erysimi Kaltenbach, 1843 (Hemiptera: Aphididae) at 15 °C, while at 25 °C, the rates were 1.747 h⁻¹ and 1.321 h⁻¹, respectively. Handling time was influenced by both temperature and predator stage. As the temperature increased, the handling time of the later predatory stages decreased. This study suggests that later predatory stages of C. septempunctatas actively hunt aphids at higher temperatures. Full article

Understanding predator–prey and predator–predator interactions is essential for evaluating the effectiveness of biocontrol agents and developing efficient pest management strategies. This study investigates the effects of prey species, predator life stage, and predator density on the predatory efficiency of the generalist predator Rhynocoris fuscipes (Fabricius) under semi-field conditions. Both the nymphs and adults of R. fuscipes consumed significantly more second-instar larvae of S. frugiperda than larvae of S. litura or M. separata. Notably, fifth-instar nymphs and adults exhibited higher predation capacity (11.75 ± 0.37 and 10.90 ± 0.40 larvae) than fourth-instar nymphs (9.05 ± 0.29 larvae) on S. frugiperda. R. fuscipes demonstrated a Type II functional response at all developmental stages toward each prey species, and fifth-instar nymphs revealed higher attack rates (a = 1.5205 ± 0.0544) on S. frugiperda; additionally, the handling time did not significantly differ among three prey species. It suggests that this predator may be more effective at controlling noctuid populations at low prey densities. As predator age and density increased, intraspecific competition among R. fuscipes also intensified. In a multi-prey system, R. fuscipes showed a marked preference for S. frugiperda over the other two prey species. These findings indicate that the fifth-instar nymphs and adults of R. fuscipes are particularly effective in suppressing early-instar larvae of the three noctuid pests, especially S. frugiperda, at low densities. This study enhances our understanding of the predation capacity and prey preference of R. fuscipes towards the three noctuid pests and provides a foundation for the development of more targeted and efficient pest management strategies using this predator. Full article

Strawberry is an important specialty crop grown in Florida. Recently, chilli thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae), have become a significant threat to Florida strawberry production. Pesticide applications are not always recommended because of the development of insecticidal resistance. Biological control can be a viable control option for this pest. However, the management of S. dorsalis using predatory bug Orius insidiosus Say (Hemiptera: Anthocoridae) has never been explored in strawberries. Therefore, this study’s aim was to evaluate the predation efficacy of O. insidiosus through daily consumption rate and the functional response while preying on S. dorsalis. The results suggest that adult O. insidiosus has a significantly higher daily consumption rate than fifth-instar nymphs when feeding on both life stages of S. dorsalis. A Type II functional response was expressed by O. insidiosus when feeding on larval and adult S. dorsalis, indicating that the predation rate can increase with the prey density before it reaches a saturation point. The attack rates (a) and prey handling time (T_h) were also computed on second-instar larvae and adult S. dorsalis, respectively. The results indicate that O. insidiosus can be used as an augmentation biocontrol agent for S. dorsalis management in strawberries. Full article

The release of herbivore-induced plant volatiles (HIPVs) has been recognized to be an important strategy for plant adaptation to herbivore attack. However, whether these induced volatiles are beneficial to insect herbivores, particularly insect larvae, is largely unknown. We used the two important highly polyphagous lepidopteran pests Spodoptera frugiperda and S. litura to evaluate the benefit on xenobiotic detoxification of larval exposure to HIPVs released by the host plant maize (Zea mays). Larval exposure of the invasive alien species S. frugiperda to maize HIPVs significantly enhanced their tolerance to all three of the well-known defensive compounds 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), chlorogenic acid, and tannic acid in maize and the two commonly used insecticides methomyl and chlorpyrifos. HIPV exposure also improved the larval tolerance of S. litura third instars to chlorogenic and tannic acids. Furthermore, larval exposure to either maize HIPVs or DIMBOA induced the activities of cytochrome P450 enzymes (P450s), glutathione-s-transferase (GST), and carboxylesterase (CarE) in the midguts and fat bodies of the two insects, while the induction was significantly higher by the two components together. In addition, the expression of four genes encoding uridine diphosphate (UDP)-glycosyltransferases (UGT33F28, UGT40L8) and P450s (CYP4d8, CYP4V2) showed similar induction patterns in S. frugiperda. Cis-3-hexen-1-ol, an important component in maize HIPVs, also showed the same functions as maize HIPVs, and its exposure increased larval xenobiotic tolerance and induced the detoxification enzymes and gene expression. Our findings demonstrate that HIPVs released by the pest-infested host plants are conductive to the xenobiotic tolerance of lepidopteran insect larvae. Hijacking the host plant HIPVs is an important strategy of the invasive alien polyphagous lepidopteran pest to counter-defend against the host plant’s chemical defense. Full article

The water lily aphid (Rhopalosiphum nymphaeae) is a highly polyphagous herbivore that causes severe damage to many terrestrial and aquatic plants, especially lotus. Due to environmental concerns about water pollution and other issues caused by chemical control methods, there is an urgent need to develop effective and sustainable control methods. The harlequin ladybird (Harmonia axyridis) is a well-known aphid predator and may pose a potential threat to R. nymphaeae. To study the predation ability of H. axyridis at different developmental stages on R. nymphaeae, we assessed the functional response, attack rate, and search effect of H. axyridis larvae and adults preying on R. nymphaeae. The numerical response of this process was also evaluated under a constant ladybird-to-aphid ratio and constant aphid density conditions, respectively. Our results showed that all predator stages exhibited type II functional responses. The predation rate of individual H. axyridis on R. nymphaeae nymphs significantly increased as prey density increased. In contrast, the search effect of H. axyridis gradually decreased with an increase in prey density. Meanwhile, H. axyridis at different developmental stages possess varying predation abilities; fourth instar and adult H. axyridis were found to be highly efficient predators of R. nymphaeae. H. axyridis adults exhibited the highest predation ability and predation rate, while both the adult and fourth-instar larvae exhibited the highest attack rate. Moreover, fourth-instar larvae exhibited the highest search effect value at initially lower prey densities, although adults surpassed them at higher prey densities. Our results also indicated that H. axyridis exhibited varying degrees of intraspecific interference and self-interference influence as predator density increases. These results strongly support H. axyridis as an effective biocontrol agent for R. nymphaeae. Full article

Sawfly species of the genus Monophadnus are specialised on Ranunculaceae plants from which the larvae can sequester furostanol saponins into the haemolymph, mainly (25R)-26-[(α-L-rhamnopyranosyl)oxy]-22α-methoxyfurost-5-en-3β-yl-O-β-D-glucopyranosyl-(1→3)-O-[6-acetyl-β-D-glucopyranosyl-(1→3)]-O-β-D-glucopyranoside (compound 1). In this work, TLC, GC-MS, and HPLC-DAD-ESI/MS analyses together with feeding, repeated simulated attacks, and ant deterrence bioassays were conducted to extend the chemoecological knowledge about two sawfly species specialised on H. foetidus L. (Monophadnus species A) and H. viridis L. (Monophadnus species B). Larvae of Monophadnus species B were mostly feeding on the squares treated with the n-butanol fraction from H. foetidus, compound 1 being its primary non-nutritional stimulant. In contrast, all H. viridis fractions stimulated feeding, with n-hexane marginally more active. β-sitosterol within n-hexane was determined as the nutritional stimulant. Quantitative analyses demonstrated that leaves of H. viridis but not H. foetidus contain the ecdysteroids 20-hydroxyecdysone and polypodine B. Moreover, the haemolymph of Monophadnus species B larvae reared on H. viridis contained the glycosides of polypodine B and 20-hydroxyecdysone at a concentration of 2.5 to 6.8 µmol/g fresh weight of haemolymph. This concentration is several thousand times higher than the concentration range of the aglycones in their host plant (3.63 × 10⁻⁴ to 2.23 × 10⁻⁴ µmol total ecdysteroids/g fresh weight of leaves), suggesting bioaccumulation. The larvae of both species fed on H. foetidus do not show any traces of ecdysteroids in their haemolymph, indicating a facultative role of these compounds in their defence as well as their inability to endogenously synthesise these compounds. The haemolymph containing ecdysteroids was a significant feeding deterrent against Myrmica rubra L. ant workers (one of their natural predators) at 0.8 mg/mL. The larvae kept effective deterrent levels of glycosylated ecdysteroids (≅175 mM) between simulated attacks on days 1 and 2, but the levels clearly decreased on day 3 (≅75 mM). Most larvae (89%) survived a first attack but only 23% a consecutive second one. As a conclusion, we report for the first time that two Monophadnus species feeding on H. viridis sequester phytoecdysteroids into the larval haemolymph in the form of glycosides. In addition, compound 1 possesses defensive and phagostimulant activities, and we present evidence for a combined effect of furostanol saponins and ecdysteroids as repellents against ants. Full article

This paper presents a three-year study concerning the effectiveness of the OSR seed treatment with the cyantraniliprole active ingredient in controlling the DBM larvae attack in autumn and four-year monitoring of the DBM flight pattern, using pheromone sticky traps. The experiment and the monitoring were conducted at the experimental field from the National Agricultural Research and Development Institute (NARDI) Fundulea in Southeast Romania. For the field assessments, each OSR sampled plant was photographed in macro mode, and then images were downloaded and magnified on the PC screen to determine the DBM larva attack. The traps were placed in the OSR crop from mid-March till December and checked twice weekly. Data from the field assessment revealed a higher pest attack on OSR plants on 11 November 2020, when the DBM larvae attack degree was 16.26% in the untreated variant and 11.24% in the variant with treated seeds. The results evidenced unusually higher activity for the diamondback moths during November 2019, 2020, and 2022; the beginning of December 2020 and 2021; and mid-December 2022. This is the first report from the Romanian scientific literature concerning higher DBM attacks at OSR plants in autumn and high moth activity during November and December. Full article

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an invasive pest native to the American continent. The present study focused on bio-intensive tactics like intercropping, using natural enemies, botanical insecticides and biopesticides for managing S. frugiperda for the organic production of maize in Indian conditions. A total of eight different parasitoids attacking the different stages of S. frugiperda viz., eggs and larvae were found in the study area. The total parasitism rate due to all the parasitoids ranged from 28.37 to 42.44%. The egg-larval parasitoid, Chelonus formosanus Sonan (Hymenoptera: Braconidae) was the dominant parasitoid (12.55%), followed by Chelonus nr. blackburni (Hymenoptera: Braconidae) (10.98%) and Coccygydium sp. (4.85%). About 36.58 percent of the egg masses collected was parasitized by egg parasitoids, among which Telenomus remus (Nixon) (Hymenoptera: Scelionidae) was the dominant parasitoid. The botanicals insecticides such as citronella and annona extract were most effective, resulting in 100% mortality of FAW larvae (168 h after treatment). The essential oil of garlic (100%) was found highly effective in inhibiting egg hatching, followed by geraniol (90.76%). The maize intercropped with lady’s finger (okra) recorded significantly the lowest pest infestation and recorded higher grain yield (6.17 q/ha) than other intercropping systems and control (5.10 q/ha). The overall bioefficacy of commercial biopesticides against the larvae of S. frugiperda was in the following order azadirachtin > Metarhizium anisopliae (Metch.) Sorokin (Hypocreales: Clavicipitaceae) > Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) at 168 h after treatment. Full article

Insect gut microbes have important roles in host feeding, digestion, immunity, development, and coevolution with pests. The fall armyworm, Spodoptera frugiperda (Smith, 1797), is a major migratory agricultural pest worldwide. The effects of host plant on the pest’s gut bacteria remain to be investigated to better understand their coevolution. In this study, differences in the gut bacterial communities were examined for the fifth and sixth instar larvae of S. frugiperda fed on leaves of different host plants (corn, sorghum, highland barley, and citrus). The 16S rDNA full-length amplification and sequencing method was used to determine the abundance and diversity of gut bacteria in larval intestines. The highest richness and diversity of gut bacteria were in corn-fed fifth instar larvae, whereas in sixth instar larvae, the richness and diversity were higher when larvae were fed by other crops. Firmicutes and Proteobacteria were dominant phyla in gut bacterial communities of fifth and sixth instar larvae. According to the LDA Effect Size (LEfSe) analysis, the host plants had important effects on the structure of gut bacterial communities in S. frugiperda. In the PICRUSt2 analysis, most predicted functional categories were associated with metabolism. Thus, the host plant species attacked by S. frugiperda larvae can affect their gut bacterial communities, and such changes are likely important in the adaptive evolution of S. frugiperda to host plants. Full article

Crop resistance and biological control are both considered efficient and environmentally friendly methods of sustainable pest control. In this study, we aimed at investigating the direct influence of four wheat lines with varying resistance level on the life-history traits of the greenbug, Schizaphis graminum, and the mediational effect on the functional response of a predatory ladybird, Propylaea japonica, under laboratory conditions. Results showed that the aphid fitness was the lowest for aphids that had been feeding on wheat line ‘98-10-19’ for one year. These aphids had the longest development time, and least adult mass, minimal mean relative growth rate, and lowest reproductive fitness. In contrast, the aphids that fed on wheat line ‘98-10-30’ were the fittest, with the shortest development time and highest levels of reproductive fitness. The predatory activities of the ladybeetle, especially the adult male significantly decreased following the consumption of aphids belonging to the ‘98-10-19’-acclimated population. However, there were no significant differences in predatory efficiency (net attack frequency) among the four aphid acclimated populations. Our results showed that the wheat line ‘98-10-19’ has a relative higher resistance to S. graminum than the other three wheat lines, which could further decrease the amount of prey available for consumption. However, the ecological effect of the resistance of ‘98-10-19’ to S. graminum posed no negative influence on the biocontrol potential of P. japonica to these aphids, as their predatory efficiency increases at the fourth instar larvae phase. Full article