Active volatile components of the preferred hosts are potential attractants to Hyphantria cunea adults.

The extraordinary adaptability and dispersal abilities have allowed Hyphantria cunea to expand its range, posing a great threat to urban landscapes and natural ecosystems. Searching for safe, efficient, and low-cost control methods may provide new strategies for pest management in H. cunea spread areas. In this study, based on the attraction of insects by preferred hosts, it was found that the response rates of virgin H. cunea female adults to Salix matsudana, Juglans mandshurica and Ulmus pumila were 89.17%, 97.92% and 93.98%, respectively. It was further found that this significant preference was mainly related to the volatiles m-xylene, o-xylene, dodecane and tetradecane found in the three species. Even though all four compounds at 10 µL/mL and 100 µL/mL had significant attractive effects on the virgin H. cunea female adults, m-xylene and dodecane at 100 µL/mL elicited significant EAG responses and tending behaviors by stimulating the olfactory receptor neurons (ORN A) of females, with response rates of 83.13% and 84.17%, while also having significant attractive effects on virgin male adults with rates of 65.74% and 67.51%. Therefore, both m-xylene and dodecane which at concentrations of 100 µL/mL had strong attractions to adults, could be used as the first choice of attractants for both sexes of H. cunea. This has important practical significance in reducing the frequency of H. cunea generations, limiting their population, controlling their spread range, and improving the efficiency of pest management in epidemic areas.

The high adaptability of Hyphantria cunea larvae to cinnamic acid involves in detoxification, antioxidation and gut microbiota response.

Hyphantria cunea is one of the most destructive invasive agricultural and forest pests worldwide. In order to better understand the adaptation mechanism of H. cunea larvae to secondary metabolites of their highly diversified host plants, the physiological function and detoxification ability of midgut, as well as the gut microbial community were investigated in H. cunea larvae fed with cinnamic acid-treated artificial diets. Our results showed that cinnamic acid treatment could not affect the growth and food utilization of H. cunea larvae, as evidenced by a non-significantly altered larval body weight and efficiency of conversion of ingested food. Evaluation of oxidative stress-related parameters (e.g. malondialdehyde and hydrogen peroxide) and midgut histopathology also clearly confirmed that cinnamic acid treatment caused no significant oxidative damage and pathological changes in the larval midgut. Variance analysis showed that cinnamic acid treatment significantly increased the content of non-enzymatic antioxidants (ascorbic acid and glutathione), the activity of antioxidant enzymes (superoxide dismutase and peroxidase) and detoxification enzyme (carboxylate esterase), as well as the abundance of several gut microbiota at the genus level (Hydrogenophaga and Acinetobacter) involved in the organic substance degradation in larval midgut. Further Pearson's correlation analysis revealed that these strongly altered gut microbiota at the genus level appeared to be significantly correlated with the detoxification and antioxidation parameters. These findings demonstrate the high adaptability of H. cunea larvae to cinnamic acid involves in detoxification, antioxidation and gut microbiota response, and indicate the existence of an extremely effective counter-defense mechanism for H. cunea larvae against the secondary metabolites of host plants.

Ultrastructural and Descriptive Study on the Adult Body Surface of Heortia vitessoides (Lepidoptera: Crambidae).

Heortia vitessoides Moore, 1885 (Lepidoptera: Crambidae) is an economically important lepidopteran pest that caused severe damage to the plantation area of Aquilaria sinensis (Lour.) Gilg, 1825 (Thymelaeaceae), resulting in extensive defoliation of the trees during an epidemic. In this study, we used scanning electron microscopy (SEM) to analyze the external morphology and ultrastructure of sensilla on various body parts of H. vitessoides. Specifically, seven, four, four, and five types of sensilla were found, respectively, on the antennae, proboscis, labial palps, and legs. We described the types, distributions, and sexual dimorphism of these sensilla on antennae, and found that the number and size of sensilla differed significantly between males and females. This study provides crucial information for future investigations into the function of these sensilla in H. vitessoides.

Response of the gypsy moth, Lymantria dispar to transgenic poplar, Populus simonii x P. nigra, expressing fusion protein gene of the spider insecticidal peptide and Bt-toxin C-peptide.

The response of the Asian gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae) to a fusion gene consisting of the spider, Atrax robustus Simon (Araneae: Hexanthelidae) ω-ACTX-Ar1 sequence coding for an ω-atracotoxin and a sequence coding for the Bt-toxin C-peptide, expressed in transgenic poplar Populus simonii x P. nigra L. (Malphigiales: Salicaceae) was investigated. Individual performance, feeding selection, midgut proteinase activity and nutrition utilization were monitored. The growth and development of L. dispar were significantly affected by continually feeding on the transgenic poplar, with the larval instars displaying significantly shorter developmental times than those fed on nontransgenic poplar, but pupation was delayed. Mortality was higher in populations fed transgenic poplar leaves, than for larvae fed nontransgenic poplar leaves. The cumulative mortality during all stages of larvae fed transgenic leaves was 92% compared to 16.7% of larvae on nontransgenic leaves. The highest mortality observed was 71.7% in the last larval instar stage. A two-choice test showed that fifth-instar larvae preferred to feed on nontransgenic leaves at a ratio of 1:1.4. Feeding on transgenic leaves had highly significant negative effects on relative growth of larvae, and the efficiency of conversion of ingested and digested food. Activity of major midgut proteinases was measured using substrates TAME and BTEE showed significant increases in tryptase and chymotrypsinlike activity (9.2- and 9.0-fold, respectively) in fifth-instar larvae fed on transgenic leaves over control. These results suggest transgenic poplar is resistant to L. dispar, and the mature L. dispar may be weakened by the transgenic plants due to Bt protoxins activated by elevated major midgut proteinase activity. The new transgenic poplar expressing fusion protein genes of Bt and a new spider insecticidal peptide are good candidates for managing gypsy moth.

The improved resistance against gypsy moth in Larix olgensis seedlings exposed to Cd stress association with elemental and chemical defenses.

BACKGROUND: Cadmium (Cd), as an environmental pollutant, can endanger various biological and chemical characteristics of plants in multiple aspects. In this study, the effects of Cd contamination or exposure for 30 and 60 days at 1, 2, 4 mg kg-1 concentrations on the resistance of Larix olgensis seedlings to the gypsy moth (Lymantria dispar) larvae were investigated. RESULTS: Our results showed that Cd stress did not significantly affect the growth and biomass parameters of the larch seedlings, which might be attributed to the scavenging mechanism of reactive oxygen species (e.g. superoxide dismutase and peroxidase). Regarding the phytochemical defense, we found that Cd stress significantly changed the contents or activities of protease inhibitors (such as trypsin and chymotrypsin inhibitors) and secondary metabolites (tannins and phenolic acids) in L. olgensis seedling needles; however, their response trends varied with Cd exposure concentrations with a significant increase at low concentrations and a significant decrease at high concentrations. Moreover, both chemical and elemental defenses contributed to the resistance of L. olgensis seedlings to the gypsy moth larvae, and their synergistic effects (between toxic elements and organic metabolites) could provide an overall improved defense of L. olgensis seedlings even at low concentrations of single components, resulting in a detrimental effect on the growth of gypsy moth larvae. CONCLUSION: These findings call for an urgent need to adjust and optimize pest control strategies in heavy metal polluted areas based on the effects of heavy metal stress on woody plant resistance to pest insects. © 2019 Society of Chemical Industry.

Evaluating the ecotoxicological effects of Pb contamination on the resistance against Lymantria dispar in forest plant, Larix olgensis.

BACKGROUND: Heavy metal contamination in forest ecosystems has become increasingly severe, and there is an urgent need to better understand the ecotoxicological effects of heavy metals on the whole forest ecosystems, especially their effects on insect resistance of forest plant. In the present study, the resistance against gypsy moth (Lymantria dispar) larvae in Larix olgensis seedlings grown in non-amended or Pb-amended (at 500 and 1500 mg kg-1 ) soil was evaluated. RESULTS: Pb from the treated soil could be transferred and exerted bio-toxicological effects along the food chain consisting of L. olgensis seedlings and gypsy moth larvae, eventually causing significantly reduction in seedlings growth, as well as larval weight, survival rate and antioxidant capacity. With regard to phytochemical defense, the activities or contents of protease inhibitors (trypsin and chymotrypsin inhibitors) and secondary metabolites (condensed tannin and total phenolics) in Pb-treated larch needles presented a tendency of 'low-promotion, high-inhibition' with the increase of Pb exposure concentration. At the same time, Pearson's correlation coefficients showed that the trade-off hypothesis on energy allocation between phytochemical defense and plant growth was not supported by the data from the L. olgensis seedlings that were exposed to Pb stress, and elemental defense might replace the dominant role of phytochemical defense in L. olgensis seedlings under Pb stress against the gypsy moth larvae. CONCLUSION: These findings emphasize ecotoxicological effects of heavy metal contaminations along the food chains (forest plants and forest defoliators), and provide a new perspective for optimizing forest pest control strategies in the heavy metal polluted regions. © 2020 Society of Chemical Industry.

Ultrastructural observations on antennal sensilla of Coleophora obducta (Meyrick) (Lepidoptera: Coleophoridae).

Coleophora obducta (Meyrick) is an important defoliator of larch in northeast China. To further describe the mechanism of insect-plant chemical communication, we observed the antennae and their sensilla of C. obducta by scanning and transmission electron microscopy. In both sexes, antennae were threadlike, and in total there were eight types of sensilla found on the antennae: Sensilla placodea, Sensilla basiconica, Sensilla coeloconica, Sensilla styloconica, Sensilla trichodea, Sensilla squamiformia, Sensilla furcatea and Böhm bristles, respectively. We described ultrastructures and discussed possible functions. We inferred from their ultrastructures as chemoreceptors that S. placodea, S. basiconica and S. trichodea were innervated by sensory neurons. The neuron of S. styloconica terminated in a tubular structure which suggested gustatory/mechanosensory function, and the terminal sensory pegs might function as contact-chemoreceptors depending on their locations.

Identification and functional characterization of an odorant receptor in pea aphid, Acyrthosiphon pisum.

The sensitive olfactory system is necessary for survival of insects. Odorant receptors (ORs) are located on the dendrites of olfactory receptor neurons and play a critical role in odor detection. Insect ORs are functionally analyzed via heterologous expression in a Xenopus oocyte system using a two-electrode voltage-clamp (TEVC) electrophysiological recording. Here, we have identified a novel OR in the pea aphid, Acyrthosiphon pisum, then we cloned and named it ApisOR4. We analyzed the ApisOR4 tissue expression patterns and found expression only in antennae tissues. Further functional analysis using TEVC revealed that ApisOR4 is broadly tuned to eight volatiles, which elicit electrophysiological response in pea aphid antennae. This study provides an initial functional analysis of aphid ORs and identifies candidate volatiles to be used in developing new strategies for aphid control.

Heavy Metal Accumulation/Excretion in and Food Utilization of Lymantria dispar Larvae Fed With Zn- or Pb-Stressed Populus alba berolinensis Leaves.

Heavy metal contaminations have attracted increasing concern worldwide due to their potential damages to the whole ecosystem. This study investigated the heavy metal-accumulation and excretion in, and food utilization of the gypsy moth (Lymantria dispar) larvae that were fed with leaves plucked from poplar seedlings (Populus alba berolinensis) grown in either noncontaminated soil (control), Zn-contaminated soil (500mg/kg), or Pb-contaminated soil (500mg/kg). Our results showed that excretion of heavy metals via insect feces and exuvia is an effective approach to reduce the internal Zn and Pb concentrations, and result in the decrease of Zn and Pb concentrations in the gypsy moth larvae with the increased larval age. In addition, the gypsy moth larvae seemed to have a strong homeostatic adjustment mechanism [between approximate digestibility (AD) and efficiency of conversion of digested food (ECD)] that maintains a stable level of "efficiency of conversion of ingested food (ECI)" regardless of heavy metal (Zn or Pb) contaminations or not, except the fifth instar larvae in which the increase in AD was insufficient to compensate for the decrease of ECD. These results suggest that heavy metal excretions could help the gypsy moth larvae cope with Zn or Pb stress, and the increased digestion of food could meet their energy requirements for both detoxification and growth. However, further increase in Zn or Pb exposure time seemed to inhibit the larval food utilization.

[Food utilization and excretion mechanism of Cd in gypsy moth larvae fed on Cd-enriched Populus albaXP. berolinensis leaves]. / Cdèƒè¿«å¯¹èˆžæ¯’è›¾å¹¼è™«é£Ÿç‰©åˆ©ç”¨çš„å½±å“åŠå ¶Cd的外泌机制.

To investigate the eco-physiological responses of phytophagous insects to host plants exposed to heavy metal stress, the gypsy moth (Lymantria dispar) larvae were reared with leaves of Populus albaXP. berolinensis grown in Cd-contaminated soil to analyze their food utilization and mechanisms underlying Cd excretion. Our results showed that after feeding on Cd-stressed poplar leaves, Cd concentrations and contents in the 3rd-6th instar larvae were significantly higher than those in control. The Cd concentrations significantly decreased with the larval age, whereas it was reverse for Cd contents. Cd concentrations in the larval faces and exuvia were significantly higher than those in control. Food digestion/consumption rate and conversion rate of the 3rd-5th instar larvae in the Cd-treatment group were significantly higher and lower than those in the control, respectively. Food utilization rate of the Cd-stressed 3rd-4th instar larvae were not significantly different from that of the control larvae with the same age. In contrast, the Cd-stressed 5th instar larvae showed a significantly lower food utilization rate than the control. These results indicated that gypsy moth larvae could remove some Cd from their bodies through effective excretion (e.g. feces and exuvia), with the mature larvae being more effective than the juveniles. The increases of larval body mass seemed to have a "dilution effect" on its Cd concentration. Under Cd stress, the gypsy moth larvae might maintain a certain level of food utilization rate for growth and development via a modulation of food consumption/conversion rates, but Cd-stress would still reduce the larval food utilization rate when it was beyond a certain threshold.

A receptor-neuron correlate for the detection of attractive plant volatiles in Helicoverpa assulta (Lepidoptera: Noctuidae).

Plant volatiles are vital cues in the location of hosts for feeding and oviposition for Lepidoptera moths. The noctuid Helicoverpa assulta is a typical polyphagous moth, regarded as a good model for studying the olfactory reception of plant volatiles. In this study, four full-length genes encoding odorant receptors HassOR24, HassOR40, HassOR41, and HassOR55 expressed in antenna in H. assulta were functionally characterized. The highly expressed HassOR40 was narrowly tuned to a few structurally-related plant volatiles: geranyl acetate, geraniol and nerolidol. By systematically analyzing responses of single neuron in both trichoid sensilla and basiconic sensilla using single sensillum recording, the specific neuron B in one type of short trichoid sensilla was found to be mainly activated by the same chemicals as HassOR40 with high sensitivity, and with no significant difference between male and female neurons. Thus, a clear "receptor-neuron" relationship in H. assulta was demonstrated here, suggesting that HassOR40/HassOrco are expressed in neuron B of short trichoid sensilla. The active tobacco volatile nerolidol, recognized by this receptor-neuron line, elicits significant behavioral attraction of both sexes in H. assulta adults. The results indicate that we identified a receptor-neuron route for the peripheral coding of a behaviorally relevant host volatile in H. assulta.

Asymmetrical distribution of antennal sensilla in the female Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae).

Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae) is an important egg parasitoid of several major insect pests. To better understand its host finding mechanisms, the antennal sensilla of female wasp were investigated by scanning electron microscopy. Sensilla chaetica were found mainly on radicle and pedicel segments of the antennae. i-Type sensilla, s. campaniformia, and corneous sensilla were detected on the leeward side, while s. coeloconica and lance sensilla were presented on the windward side of the antennae. S. trichodea and s. basiconica were more abundant on the leeward side than on the windward side of the antennae. More s. placodea were found on the windward side than on the leeward side of the right antenna, while the opposite results were observed on the left antenna. Overall, more s. placodea were found on the right antenna than that on the left antenna. The numbers of s. trichodea and s. basiconica on the clava or the third flagellum antennomere of the right antenna were more than those of the left antenna, whereas their distribution patterns on the other corresponding antennomeres were reverse. Our results showed that there is a strong asymmetrical antennal sensilla distribution quantitatively and spatially between the left and right antennae. Placoid sensilla are present more on the right antenna than on the left antenna. S. campaniformia, corneous sensilla, and i-type sensilla were found only on the leeward side of the antennal clava, while their external morphology and potential functions were described and discussed in detail for the first time.

Antennal sensilla of the pine weevil Pissodes nitidus Roel. (Coleoptera: Curculionidae).

The antennal sensilla of the pine weevil (Pissodes nitidus Roel.) were observed with scanning electron microscopy and transmission electron microscopy (TEM). The weevil antenna consists of a long scape, a pedicel, and a flagellum with 10 segments; the last four flagellum segments are fused, forming the antennal club, which is densely covered by various sensilla. In both sexes, six types of sensilla, sensilla palmate 1-4, sensilla chaetica, sensilla trichoid, sensilla basiconic 1-2, sensilla rod-like 1-3, sensilla falciform, were identified. Sensilla palmate represent a unique sensillum type in the Pissodes genus, and named here after their palmate shape, also represent the most abundant sensillum type. The TEM analysis of sensilla palmate represents the first such analysis of this sensillum type, and we speculate that the sensilla have an olfactory function. The sensilla trichoid and chaetica were evenly distributed on the three or four hair bands of the club, with much lower numbers than the palmate sensilla. No significant sexual differences in the types, numbers, and distribution of the antennal sensilla were found except for the size. TEM observation indicated that sensilla chaetica and trichoid may function as olfactory sensors. The putative functions of other sensilla type were also discussed with reference to their morphology, distribution, and ultrastructure.

[Effects of different elicitors on olfactory response and oviposition selection of Dendrolimus superans (Butler)].

This paper studied the behavioral responses of Dendrolimus superans larvae and adults to Z-jasmone, methyl jasmonate (MeJA) and methyl salicylate (MeSA), and to Larix gmelinii seedlings treated with different elicitors including mechanic wounding, insect feeding, jasmonic acid (JA), salicylic acid (SA), Z-jasmone, MeJA, MeSA, and JA + SA. The results showed that D. superans larvae were repelled by MeJA and MeSA at the concentrations of 0.1%-10% V/V. L. gmelinii seedlings were induced resistance by wounding, JA, MeJA, Z-jasmone and MeSA, which decreased the feeding selection of D. superans larvae. D. superans adults exploited evident electroantennogram (EAG) responses to Z-jasmone and MeSA, and the sensitivity of the females was enhanced with the increasing concentration of Z-jasmone and MeSA. Significantly low amount of eggs was observed on the L. gmelinii seedlings treated with test elicitors.