Journal of economic entomology最新文献

The spatiotemporal variability in resistance to Sitobion miscanthi (Takahashi) among wheat germplasm poses a substantial challenge for wheat breeders attempting to efficiently select and utilize existing germplasm in the development of aphid-resistant wheat varieties. The genetic composition and phenotypic traits of aphid populations within the same wheat field exhibit annual fluctuations, which may explain the unstable field resistance of wheat germplasms to S. miscanthi. In this study, the host adaptability of 4 aphid populations collected from the same wheat field in Yangling, Shaanxi Province, at different time points was evaluated across 5 wheat varieties and 3 barley varieties. The results showed that, following aphid infestation on day 14, the 4 aphid populations exhibited significant differences in their abundance on all host plants except the barley variety Xiyin-2. On day 24, the 4 aphid populations differed significantly in their abundance, total biomass, and mean individual biomass across all host plants. Distinct host-specific differentiation patterns were observed among the 4 populations based on their abundance on days 14 and 24, as well as total and mean individual biomass on day 24. Overall, significant differences in host adaptability were observed among populations sampled from the same field at different times, providing preliminary evidence that temporal variation in aphid population composition may directly contribute to the unstable resistance performance of wheat germplasm under field conditions.

Longevity critically influences biocontrol efficacy, yet direct artificial selection for lifespan extension has rarely been documented in natural enemies. Here, we established long-lived lines of the parasitoid wasp Pachycrepoideus vindemmiae through artificial selection and investigated their phenotypic and genomic consequences. Two longevity-selected lines (LL1 and LL2) and their corresponding original control lines (OL1 and OL2) were generated. Females of LL1 showed a significantly extended lifespan by the fifth generation, whereas LL2 did not respond to selection. Notably, the longevity advantage of LL1 females persisted at generations 15 and 33 after cessation of selection. LL1 females also exhibited increased lifetime fecundity and enhanced resistance to cold and starvation, without changes in developmental duration, sex ratio, or body size. To explore the genetic basis of these traits, whole-genome resequencing was conducted on females and males from LL1 and OL1 at generation 33. Population genomic analyses revealed clear genetic differentiation between lines but not between sexes within lines. Selective sweep analyses in females identified genomic regions under selection enriched in energy metabolism and stress regulation, and integration with expression data revealed SNP variation and line-specific cold-induced expression of heat shock protein genes. Together, these results indicate that artificial selection can potentially produce a stable extension of female lifespan in P. vindemmiae, accompanied by distinct genomic signatures in the responsive line. Our findings provide insights into the genetic architecture of longevity and stress resistance in parasitoid wasps while highlighting both the opportunities and constraints of artificial selection for biological control improvement.

Insects possess an intricate and efficient olfactory system that plays a critical role in navigating their environment, facilitating host location, defensive maneuvers, and reproductive behaviors. In the present study, 12 biological samples were successfully sequenced, yielding a total of 79.92 G data. This led to the assembly of 46,291 Unigenes, with a cumulative length of 47,102,395 base pairs. These Unigenes were subsequently annotated across seven functional databases, including NR (22,104), Swissprot (16,203), KEGG (7,652), KOG (14,597), eggNOG (19,129), GO (14,852), and Pfam (15,267). Central to our findings, 33 genes associated with olfaction were identified, comprising 16 odorant binding proteins (OBPs), 13 chemosensory proteins (CSPs), 3 ionotropic receptors (IRs), and 1 sensory neuron membrane protein (SNMP). Given the critical role of volatile organic compounds emitted by ancient tea leaves in host plant location, the volatile components of these trees using HS-SPEM-GC-MS were further analyzed. The primary volatile identified were alcohols, aldehydes, esters, alkanes, olefins, ketones, and nitriles, with linalool (14.02%), (E)-hexenal (2.84%), and α-farnesene (6.75%) emerging as the predominant compounds. To understand the molecular interactions underlying the recognition of these compounds, molecular docking simulations were conducted, focusing on the three aforementioned compounds and three specific OBPs (OBP3, OBP4, and OBP7) from the tea green leafhoppers. Notably, α-farnesene exhibited the highest binding affinity with OBP7, with the binding process stabilized by the synergistic effects of hydrophobic and hydrogen bonding forces. These findings deepen our understanding of the olfactory recognition mechanisms employed by tea green leafhoppers in their interaction with ancient tea plants.

European corn borer, Ostrinia nubilalis Hübner, is a major pest of maize (Zea mays L.) in North America that has been managed using transgenic maize producing insecticidal toxins from Bacillus thuringiensis Berliner (Bt) for over 25 years. The first case of field-evolved resistance of O. nubilalis to a Bt toxin, Cry1Fa, was discovered in Nova Scotia, Canada, in 2018. The objectives of this study were to determine the inheritance and fitness of the first field-evolved Cry1Fa-resistant strain of O. nubilalis. Fitness characteristics such as lifespan, fecundity, and developmental time were compared among homozygous Cry1Fa-resistant, homozygous Cry1Fa-susceptible, and heterozygous reciprocal lines of O. nubilalis. Cry1Fa-resistance was found to be recessive based on diet-overlay and tissue bioassays. The homozygous Cry1Fa-resistant strain had 2.4 times greater fecundity, 2 day longer adult lifespan, and 6.5 day longer developmental time than the homozygous Cry1Fa-susceptible strain. Cry1Fa-resistant populations are expected to have 1.6 times greater net reproductive rate than Cry1Fa-susceptible populations. These results suggest that limited fitness costs are associated with field-evolved Cry1Fa-resistance, therefore the spread of resistant populations should be urgently managed.

Manipulation of genes involved in regulating pigmentation can create externally visible markers of successful gene editing. However, such engineered mutations can have secondary impacts on key traits that are undesirable, especially if the mutants are expected to compete with wild-type (WT) individuals, such as might occur with a genetic sterile insect technique. Here, we tested for negative impacts in Lygus hesperus Knight from the knockout of aralkylamine N-acetyltransferase (aaNAT), needed to convert dopamine to N-acetyldopamine (NADA) sclerotin. Knockdown of this gene was previously shown to produce entirely black versions of this significant crop pest. Here, we compared knockout (KO) and WT strains across numerous behavioral and physiological traits. In most regards, the 2 strains were quite similar, with adults exhibiting equivalent locomotor activity, sperm production, mating activity, and susceptibility to heat, desiccation, and predation. However, some differences were observed with the aaNAT KO strain relative to the WT strain; eggs were more likely to hatch, nymphs had higher rates of survival to adulthood, adults lived longer, females produced fewer eggs, and males had a higher rate of mating success. Overall, the results suggest the aaNAT KO is a suitable marker that may facilitate rapid screening of gene edits and the development of population suppression systems.

Trans-cinnamic acid and its derivatives were investigated against Solenopsis invicta Buren (RIFA), Solenopsis richteri Forel (BIFA), and reproductively functional hybrid (HIFA) for their repellency and toxicity. A range of serial concentrations starting from 156 µg/g to the failure of treatments were evaluated. Removal of treated sand in a digging bioassay was used as the criterion for repellency. Treatments were considered active until the removal of treated sand became similar to that in the ethanol control. Based on sand removal, trans-cinnamic acid, benzyl cinnamate and phenethyl cinnamate failed at 156 µg/g, whereas isoamyl cinnamate was active at 19.5, 19.5, and 39 µg/g against RIFA, HIFA, and BIFA workers, respectively. Isopropyl cinnamate and η-butyl cinnamate were active at 19.5, 39, and 39 µg/g against RIFA, HIFA, and BIFA workers, and ethyl cinnamate at 9.8, 19.5, and 39 µg/g against HIFA, RIFA, and BIFA, respectively. DEET failed at 31.25, 62.5, and 15.6 µg/g against RIFA, BIFA, and HIFA, respectively. Ethyl cinnamate, with LC50 value of 54.8, 60.9, and 70.4 µg/g showed toxicity, followed by isopropyl cinnamate (LC50 = 71.1, 69.3, and 74.7 µg/g), η-butyl cinnamate (LC50 = 128.2, 86.1, and 134.2 µg/g) and isoamyl cinnamate (LC50 = 95.8, 142.1, and 139.2 µg/g) against RIFA, BIFA, and HIFA workers, respectively. Fipronil was more toxic with LC50s of 0.43, 0.33, and 0.51 µg/g against RIFA, BIFA, and HIFA workers, respectively. Trans-cinnamic acid, benzyl cinnamate, and phenethyl cinnamate did not cause any mortality at 156 µg/g. In residual bioassays, isoamyl and η-butyl cinnamate at 312 μg/g suppressed the digging activity for more than 3 wk. Different formulations of active cinnamates be further evaluated under field conditions.

The black cocoa ant, Dolichoderus thoracicus (Smith, 1860) (Hymenoptera: Formicidae) is a pest species capable of reaching high population densities in diverse habitats. In Taiwan, infestations are associated with intrusions into residential homes, damage to electrical equipment, and decreased agricultural productivity. Although baiting programs using borax-based or boric acid-based ant baits have been implemented, these efforts often yield unsatisfactory results. This study evaluated the potential of caffeine, a naturally occurring bioactive compound, as an active ingredient in ant baits for controlling D. thoracicus and Anoplolepis gracilipes (Smith, 1857). Laboratory bioassays demonstrated that hydrogel baits containing 1.0% caffeine resulted in 100% worker mortality in D. thoracicus colony fragments within 15 days (mean survival time = 3.06 days) and complete queen mortality within 5 days (mean = 2.89 days), outperforming baits containing 0.5%, 1.5% caffeine, or 3.0% borax. These findings demonstrate that the exceptionally high attractiveness of a 1.0% caffeine bait can induce substantial worker mortality through direct consumption, leading to complete elimination of laboratory colonies of D. thoracicus despite limited trophallaxis. Additionally, the 1.0% caffeine bait was also highly effective against A. gracilipes. In conclusion, ant bait formulated with an intermediate dose of caffeine provides an optimal balance between bait acceptance and toxicity, making it a promising tool for managing D. thoracicus and other pest ant species, although further field validation is warranted.

Psix saccharicola Mani (Hymenoptera: Scelionidae) is a key parasitoid of stink bugs eggs in Iranian pistachio orchards, especially Acrosternum arabicum Wagner (Hemiptera: Pentatomidae). Cold storage of host and parasitoid life stages can facilitate parasitoid production and assist application timing in augmentation programs. We tested the suitability of A. arabicum eggs stored at -20 °C and -80 °C for periods of 0 to 90 d for parasitism by P. saccharicola. The fecundity of F1 females declined with duration of host egg storage, more so at -80 °C than at -20 °C, and so did immature survival and sex ratio. Duration of egg storage, but not temperature, affected the survival of F2 parasitoids. The 24-h fecundity of F2 females, their progeny survival and sex ratio, did not differ from controls even when parental host eggs were stored for 60 d at -20 °C, but the sex ratio was reduced by storage for 15 d at -80 °C. Parasitoid storage as pupae at either 6 °C or 8 °C for 0 to 28 d (with 2 h daily at 27 °C) had no effect on 24-h fecundity, percent parasitism, or sex ratio, but survival declined with storage time, falling to ca. 30% and 50% after 28 d at 6 °C and 8 °C, respectively. Progeny sex ratio of the F2 generation declined progressively with storage duration at 6 °C, but not at 8 °C, whereas other fitness measures were unaffected. We conclude that the use of frozen host eggs and refrigerated pupae could facilitate the rearing and augmentation of P. saccharicola against stink bug pests of pistachio.

Methyl bromide (MB) is a primary fumigant for wood quarantine in Korea. Due to international regulations targeting ozone-depleting and toxicity effects of MB, alternative fumigants are required. The study assessed the insecticidal and synergistic effects of sulfuryl fluoride (SF) and ethyl formate (EF), alone and in combination, against the long horned wood-boring beetle Monochamus alternatus and for comparison the lessor grain borer, Rhyzopertha dominica; combined fumigation in up-scaled conditions informed phytosanitary treatment standards. Individual treatments at 23 °C indicated 99% lethal concentration × time (LCt99%) products of 3,933.0 mg h/liter for the most tolerant M. alternatus eggs to SF. R. dominica eggs exhibited greater tolerance to EF than M. alternatus and the pupae were the most tolerant (EF LCt99%: 1,057.0 mg h/liter). The mixed treatment applied with EF for egg control and SF for pupal control. Mixed treatments with adjusted Ct values showed synergistic ratios ≤1.0 across most combinations, indicating no additive or synergistic interactions. The combined SF+EF application achieved complete mortality in all R. dominica life stages at a dosage of 20 + 150 mg/liter for 24 h. Concentration × Time (Ct) product of the SF+EF combination was calculated to be 629.7 + 630.9 mg h/liter, with effective control of R. dominica at a lower dosage than individual treatments, indicating its applicability to M. alternatus. This approach may represent a promising phytosanitary treatment standard for MB replacement.

"Candidatus" Liberibacter spp. infect crop plants and the psyllid vector, and at least 2 species have been shown to be susceptible to RNAi. Here, the knockdown efficacy was analyzed of 4 genes essential for insect physiological processes, vacuolar ATPase (V-ATPase) subunit genes A, B, D, and E, for potential biopesticide activity against the potato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae). Adults and third instar psyllids were given a 48-h ingestion-access period (IAP) on either single or stacked dsRNAs to compare knockdown effects. While adults showed no significant mortality, 10-d post IAP on the individual dsRNAs, mortality was significantly greater post-IAP on the stacked dsRNAs compared to negative controls. Oviposition of dsRNA-treated females was reduced by 50% to 70%, however, there was no significant difference between the single and stacked dsRNA treatments. Adult and third instar psyllids exhibited 58% and 45% mortality, respectively, post-IAP on the 4 stacked dsRNAs. In contrast, only third instar nymphs showed significant mortality after individual dsRNAs targeting V-ATPase subunits, at 42% for subunit A and 35% for subunits D and E. In general, gene silencing was more robust in potato psyllid nymphs compared to the adults. Although gene knockdown was moderately lower following an IAP on dsRNAs delivered singly, IAP on stacked dsRNAs resulted in equal or greater mortality in both psyllid life stages. These findings highlight the potential for delivering multiple dsRNAs to suppress genes involved in essential cellular processes and enhance RNAi efficacy in insects.