Journal of Pest Science最新文献

Abstract

Zoophytophagous predators can induce plant defence responses through phytophagous feeding. Since the zoophytophagous bug Orius sauteri lays eggs into plant tissues, we hypothesised that its oviposition behaviour may also induce plant defence responses with a negative impact on subsequent herbivore attacks. Pre-inoculation of O. sauteri females on tomato plants significantly reduced the fitness and reproduction of Frankliniella occidentalis, which also preferred the non-inoculated plants in indoor micro-environments. In the field, O. sauteri pre-inoculation also caused reduced population growth of F. occidentalis. All these tendencies were weaker with male compared to female O. sauteri pre-inoculation. Next, a transcriptome analysis showed that the MAPK signalling pathway, the plant hormone signal transduction and plant-pathogen interaction of defence-related pathways were significantly enriched in plants inoculated with O. sauteri females compared to untreated plants. We showed that three key genes of the JA pathway, allene oxide synthase (AOS), jasmonate ZIM-domain 2 (JAZ2), and proteinase inhibitor 1 (PI-1), were upregulated. This is evidence of plant defence activation, the likely mechanism by which O. sauteri pre-inoculation (through feeding and oviposition activities) reduced F. occidentalis fitness in the laboratory and population densities by almost three times in a greenhouse experiment. This mechanism could be promoted in IPM strategies through the early introduction of zoophytophagous biocontrol agents activating crop plant defences to enhance biological pest control.

Myzus persicae and Aphis gossypii (Hemiptera: Aphididae) are two of the most significant aphid species acting as vectors for plant viruses in vegetable crops worldwide. This work provides new knowledge relating the persistence (including population growth and survival) and impact on aphid probing and feeding behaviour of plant essential oil-derived products. Modifications in M. persicae behaviour (EPG results) were noted in plants treated with 0.2% nanoemulsions of distilled lemon oil: (1) the non-probing activity lasted longer, (2) both non-phloematic probing and phloem ingestion activities of aphids were shorter, and (3) xylem ingestion activity and the time taken to achieve sustained phloem ingestion appear to be longer. Finally, a slight increase was also observed in the mean duration of the non-probing activity of M. persicae on plants treated with 0.2% nanoemulsions of farnesol. When pepper plants were sprayed with a 0.2% nanoemulsion of farnesol with Tween 80^® (1:2), the population growth of M. persicae colonies on treated plants was slower (40 aphids/plant) than on controls (60 aphids/plant) up to the day seven. The slope of the aphid population growth line corresponding to the formulated mixture of bioactive volatiles was lower (2.26 b) and statistically significant in comparison with the control (7.09 a), probably due to a controlled-release effect up to day 14. No systemic effects were obtained for the bioactive volatiles tested.

Sextonia rubra is an Amazonian tree known for the larvicide activity of its wood extracts against Aedes aegypti. However, the lipophilic character of this extract presents an obstacle to the development of vector management products. The purpose of this study was to assess the feasibility, efficacy, and selectivity of a water-soluble formulation based on a S. rubra wood extract characterized by its larvicidal compounds rubrenolide and rubrynolide. Using reference and wild strains, larval mortality, oviposition behavior, hatching response, and fitness of mosquitoes exposed to the extract were evaluated. Laboratory eco- and cytotoxicity bioassays were performed concurrently. The extract showed larvicidal efficacy and no repulsive effect on oviposition, thus supporting its use in the treatment of breeding sites. The formulation exhibited strong acute toxicity, leading to 100% larval mortality in 2–4 days in either the dry or rainy season at a test dose of 102 µg/ml under semi-operational conditions, with residual activity maintained during the 5 weeks of testing. The formulation allowed for a noticeable gain in selectivity compared with the extract, with lower immobilization rates for Daphnia magna and Chironomus riparius, and no significant toxicity towards human cell lines (IC₅₀ > 100 µg/ml). These results highlight the potential of the S. rubra-based formulation for the management of Ae. aegypti larvae, including strains showing resistance to conventional insecticides.

Nematodes from the genus Meloidogyne are extremely harmful to agricultural crops due to their wide geographic distribution, variety of hosts, and strong reproductive capacity. The most used phytonematoid control method is the application of nematicides, which can also affect human health and the environment. Selenol ester derivatives have pharmaceutical applications, but little is known about their biological activities. We examined whether six selenol ester derivatives were nematicidal and ovicidal to the nematodes Caenorhabditis elegans and Meloidogyne incognita, and determined their toxicity to non-target organisms. The compound Se-p-methyl phenylselenobenzoate (2e) exhibited the lowest nematicidal and ovicidal Lethal concentration (LC50) to C. elegans (4.42 and 0.56 mg/L, respectively) and M. incognita (4.6 and 2.77 mg/L, respectively), which were similar or lower than the LC50 values for the control treatment with fluensulfone in C. elegans (4.07 and 6.05 mg/L, respectively) and M. incognita (43.07 and 49.63 mg/L, respectively). Compound 2e efficiently controlled the phytoparasite in greenhouse and reduced the number of galls and eggs present in tomato roots. Compared with the negative control, compound 2e was not toxic to other organisms such as Chlorella vulgaris algae, Galleria mellonella and Aedes aegypti larvae, and the aquatic protozoan Tetrahymena pyriformis. Our findings indicate that the selenol ester derivatives are potent and effective nematicides with no toxicity to the non-target organisms tested.

Semiochemicals are dominant cues for insects to locate food, mates, predators, and oviposition sites. In the modern genomic era, semiochemicals have been identified not only by the conventional chemical ecology based on bioassay-guided protocols but also by reverse chemical ecology started with deorphanization of olfactory proteins with high olfactory sensitivity and selectivity. The Scarab beetle, Anomala corpulenta, is a polyphagous pest, posing a substantial economic burden to agricultural, horticultural, and forestry industries. Here, we focused on four odorant receptors (ORs) abundantly expressed in the antennae. We heterologously expressed them in Xenopus oocytes and examined their responses to a panel of 22 odorants. Of the ORs, AcorOR29 was specifically tuned to a common floral compound, phenethyl propionate (PEP). Further, gas chromatography coupled with electroantennographic detection showed that PEP elicited a strong electrophysiological response from antennae. Y-tube olfactometer assay and field trap experiment demonstrated that PEP is attractive for both sexes of A. corpulenta across a wide range of concentrations, potentiating PEP in practical applications. Our results show that the reverse chemical ecology approach is effective in identifying semiochemicals for A. corpulenta, which would help to formulate novel strategies to control this pest.

Abundance on and access time to the host plant are the pivotal factors in Xylella fastidiosa transmission to olive by the meadow spittlebug Philaenus spumarius. Therefore, olive varieties suitable for the vectors, i.e., plants providing all the necessary cues to the insect for their location, settling and acceptance, and devoid of antixenotic defenses, could be more susceptible to infection than varieties non- or less suitable for the vector. Here we evaluated whether a bacterium-susceptible olive variety, Ogliarola Salentina, could be a more suitable host for P. spumarius than the two resistant varieties Leccino and FS-17. We carried out: (i) an evaluation of between-hosts and within-host preference; (ii) an insect survival analysis; (iii) an Electrical Penetration Graph (EPG)-assisted analysis of the probing behavior; (iv) light microscopy of the tissues the spittlebugs had access to; (v) an analysis of the xylem sap primary metabolites. In choice tests, the insect exhibited a significant preference for Ogliarola Salentina. In addition, spittlebugs displayed longer xylem sap ingestion bouts on the bacterium-susceptible variety compared to resistant genotypes, possibly because of differences in the xylem sap chemical profile rather than xylem anatomy. Spittlebugs preference for Ogliarola over both Leccino and FS-17 could be a relevant and so far overlooked component of the low disease prevalence in these two olive varieties reported in Southern Italian olive orchards. Overall, our data point toward the importance of incorporating studies on vector-plant interaction and host traits of resistance to the vector in research on genotypes resistant to X. fastidiosa.

Abstract

The Asian corn borer (ACB), Ostrinia furnacalis, is a serious maize pest in Southeast Asia, responsible for substantial economic losses to the maize crop every year. To establish insect biocontrol programmes, it is crucial to determine the ideal numbers and developmental stage of natural enemies to release. The purpose of the present study was to assess the parasitism ability of Trichogramma dendrolimi and Trichogramma ostriniae, which are the most promising biocontrol agents of the ACB, under two different methods of inundative release in maize fields. A total of 10,000 wasps of both species were released using two different methods, i.e. wasps at the same developmental stage (SDS) and wasps at different developmental stages (DDS). The results showed that T. dendrolimi wasps exhibited significantly higher parasitism of ACB eggs when they were released with the DDS method than when they were released with the SDS method. In the SDS release method, T. dendrolimi parasitized ACB eggs for only 3 days after release, while in the DDS release method, parasitism of ACB eggs occurred for 6 days. However, the two release methods had no significant impact on the performance of T. ostriniae in maize fields. In both release methods, T. ostriniae parasitized a high percentage of ACB eggs. The results of the present study clearly indicate that the poor field performance of T. dendrolimi due to the host-age factor can be improved using the DDS release method.

Understanding the composition and dynamics of ecological communities is challenging because of the large number of organisms present and their numerous interactions. Among agricultural systems, intercropping considerably increases the complexity of communities compared to monocultures and alternative host plants can influence insect pest damage. Using literature records, we construct and analyse connectance trophic webs of date palm (Phoenix dactylifera) agro-ecosystems, including and excluding intercrops. Estimates of connectance (community complexity) are relatively low and little affected by consideration of intercrops. Plant–herbivore overlap is relatively high, suggesting that herbivores are typically not specialists. Herbivore–natural enemy overlap is greater when intercrops are considered, suggesting that diffuse apparent competition regulates pest populations. We pay particular attention to how trophic web structure might affect Batrachedra amydraula (Lesser date moth), an important economic pest. Records indicate it having 15 species of natural enemies and sharing 9 of these with other herbivores; these may maintain populations of natural enemies when the moth is seasonally rare, contributing to pest suppression. The estimated potential for apparent competition between the lesser date moth and other herbivores is higher when intercrops are considered. The consequent expectation of less severe infestations in plantations that are intercropped compared to monocultures matches empirically derived reports. Further, comparing results obtained from the literature on one country (Oman) and from 15 Middle Eastern countries, we find that community metric estimates are relatively little affected by the geographical scale considered. Overall, our results suggest that literature-based trophic web construction can provide an efficient and robust alternative, or in addition, to direct empirical methodologies and that the presence of intercrops will contribute to major pest suppression via indirect apparent competition.