Search

Biopesticides based on RNA interference (RNAi) took a major step forward with the first registration of a sprayable RNAi product, which targets the world's most damaging potato pest. Proactive resistance management is needed to delay the evolution of resistance by pests and sustain the efficacy of RNAi biopesticides. [ABSTRACT FROM AUTHOR]

Simple Summary: Insecticide resistance stands as one of the most notable evolutionary phenomena for researchers. Two closely related species pests, Phthorimaea operculella and Phthorimaea absoluta, both feeding on potato crops, have developed distinct resistance mechanisms. In this study, we compared the presence of target-site mutations in P. operculella and P. absoluta in three common insecticide targets, Ace1 (acetylcholinesterase), VGSC (voltage-gated sodium channel), and RDL (GABA-gated chloride channel). Unexpected genetic divergence in target-site mutations was observed between the two species. P. absoluta had three Ace1 mutations (A201S, L231V, and F290V), four VGSC mutations (M918T, L925M, T928I, and L1014F), and one RDL mutation (A301S). On the other hand, P. operculella had Ace1 mutations (F158Y, A201S, and L231V) and only one VGSC mutation (L1014F) at lower frequencies, with no mutations detected in RDL. These findings deepen our understanding of evolutionary dynamics in pest species and offer potential strategies for more precise and sustainable pest control in potatoes. Potatoes hold the distinction of being the largest non-cereal food crop globally. The application of insecticides has been the most common technology for pest control. The repeated use of synthetic insecticides of the same chemical class and frequent applications have resulted in the emergence of insecticide resistance. Two closely related pests that feed on potato crops are the potato tuber moth, Phthorimaea operculella, and the tomato leafminer, Phthorimaea absoluta (syn. Tuta absoluta). Previous studies indicated the existence of insecticide resistance to various classes of insecticides including organophosphates, carbamates, and pyrethroids in field populations of P. operculella and P. absoluta. However, the exact mechanisms of insecticide resistance in P. operculella and to a lesser extent P. absoluta remain still poorly understood. Detecting resistance genotypes is crucial for the prediction and management of insecticide resistance. In this study, we identified multiple genetic mutations related to insecticide resistance in two species of Phthorimaea. An unexpected genetic divergence on target-site mutations was observed between P. operculella and P. absoluta. Three mutations (A201S, L231V, and F290V) in Ace1 (acetylcholinesterase), four mutations (M918T, L925M, T928I, and L1014F) in VGSC (voltage-gated sodium channel), and one mutation (A301S) in RDL (GABA-gated chloride channel) have been detected with varying frequencies in Chinese P. absoluta field populations. In contrast, P. operculella field populations showed three mutations (F158Y, A201S, and L231V) in Ace1, one mutation (L1014F) in VGSC at a lower frequency, and no mutation in RDL. These findings suggest that pyrethroids, organophosphates, and carbamates are likely to be ineffective in controlling P. absoluta, but not P. operculella. These findings contributed to a deeper understanding of the presence of target-site mutations conferring resistance to commonly used (and cheap) classes of insecticides in two closely related potato pests. It is recommended to consider the resistance status of both pests for the implementation of resistance management strategies in potatoes. [ABSTRACT FROM AUTHOR]

The potato tuberworm, Phthorimaea operculella Zeller, is an oligophagous pest feeding on crops mainly belonging to the family Solanaceae. It is one of the most destructive pests of potato worldwide and attacks foliage and tubers in the field and in storage. However, the lack of a high-quality reference genome has hindered the association of phenotypic traits with their genetic basis. Here, we report on the genome assembly of P. operculella at the chromosomal level. Using Illumina, Nanopore and Hi-C sequencing, a 648.2 Mb genome was generated from 665 contigs, with an N50 length of 3.2 Mb, and 92.0% (596/648.2 Mb) of the assembly was anchored to 29 chromosomes. In total, 16619 genes were annotated, and 92.4% of BUSCO genes were fully represented. The chromosome-level genome of P. operculella will provide a significant resource for understanding the genetic basis for the biological study of this insect, and for promoting the integrative management of this pest in future. Measurement(s) whole genome sequencing Technology Type(s) Illumina NovaSeq. 6000 • Oxford Nanopore Sequencing Sample Characteristic - Organism Phthorimaea operculella Sample Characteristic - Location Yunnan Province, Southwest China [ABSTRACT FROM AUTHOR]

BACKGROUND Damage by the potato tuber moth Phthorimaea operculella is one of the major constraints to commercial production of potato in many areas of the world. To promote effective pest management practices for P. operculella based on host plant, larval and adult performance of P. operculella fed on Lishu 6, Hezuo 88, Yunshu 304, and Qingshu 9 potato varieties was compared by examining their survival rate, larval feeding, pupal weight, and oviposition preference. RESULTS: Compared with larvae fed on the other three potato plants, those fed on Lishu 6 exhibited the highest survival rate, with almost 61.67% developing to the adult stage. Females also preferred to lay their eggs on Lishu 6 over Hezuo 88, Yunshu 304 and Qingshu 9; and the weight of P. operculella pupa on Lishu 6 plant (0.0085 g) was significantly heavier than that of on others, especially on Qingshu 9 (0.0062 g). Moreover, first instar larvae fed on Lishu 6 showed host preference to Qingshu 9. CONCLUSION: This study demonstrated that Lishu 6 is susceptible to P. operculella, and Qingshu 9 is not relatively susceptible to P. operculella, which suggested that the P. operculella feeding responses to dominant potato varieties in China is different. This variation can be applied for the potato breeding and pest management practice. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Species displacement by the outcome of interspecific competition is of particular importance to pest management. Over the past decade, spinetoram has been extensively applied in control of the two closely related thrips Megalurothrips usitatus and Frankliniella intonsa worldwide, while whether its resistance is implicated in mediating interspecific interplay of the two thrips remains elusive to date. RESULTS: Field population dynamics (from 2017 to 2019) demonstrated a trend toward displacement of F. intonsa by M. usitatus on cowpea crops, supporting an existing interspecific competition. Following exposure to spinetoram, M. usitatus became the predominate species, which suggests the use of spinetoram appears to be responsible for mediating interspecific interactions of the two thrips. Further annual and seasonal analysis (from 2016 to 2020) of field‐evolved resistance dynamics revealed that M. usitatus developed remarkably higher resistance to spinetoram compared to that of F. intonsa, implying a close relationship between evolution of spinetoram resistance and their competitive interactions. After 12 generations of laboratory selection, resistance to spinetoram in M. usitatus and F. intonsa increased up to 64.50‐fold and 28.33‐fold, and the average realized heritability (h2) of resistance was calculated as 0.2550 and 0.1602, respectively. Interestingly, two‐sex life table analysis showed that the spinetoram‐resistant strain of F. intonsa exhibited existing fitness costs, but not the M. usitatus. These indicate that a rapid development of spinetoram resistance and the lack of associated fitness costs may be the mechanism underlying recent dominance of M. usitatus over F. intonsa. CONCLUSION: Collectively, our results uncover the involvement of insecticide resistance in conferring displacement mechanism behind interspecific competition, providing a framework for understanding the significance of the evolutionary relationships among insects under ongoing changing environments. These findings also can be invaluable in proposing the most appropriate strategies for sustainable thrips control programs. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Pheromones are a kind of signal produced by an animal that evoke innate responses in conspecifics. In moth, pheromone components can be detected by specialized olfactory receptor neurons (OSNs) housed in long sensilla trichoids on the male antennae. The pheromone receptors (PRs) located in the dendrite membrane of OSNs are responsible for pheromone sensing in most Lepidopteran insects. The potato tuber moth Phthorimaea operculella is a destructive pest of Solanaceae crops. Although sex attractant is widely used in fields to monitor the population of P. operculella , no study has been reported on the mechanism the male moth of P. operculella uses to recognize sex pheromone components. In the present study, we cloned two pheromone receptor genes PopeOR1 and PopeOR3 in P. operculella. The transcripts of them were highly accumulated in the antennae of male adults. Functional analysis using the heterologous expression system of Xenopus oocyte demonstrated that these two PR proteins both responded to (E , Z)-4,7–13: OAc and (E , Z , Z)-4,7,10–13: OAc, the key sex pheromone components of P. operculella , whilst they responded differentially to these two ligands. Our findings for the first time characterized the function of pheromone receptors in gelechiid moth and could promote the olfactory based pest management of P. operculella in the field. [ABSTRACT FROM AUTHOR]

The Asian corn borer, Ostrinia furnacalis, is a serious pest and is widely distributed in corn-producing regions throughout China. This insect enters facultative diapause as fully grown larvae in response to short day lengths. Here, we evaluate the changes in diapause incidence and critical day length (CDL) by crossing a tropical strain with five subtropical and temperate strains from a 2897-km latitudinal gradient to investigate the latitudinal variations in diapause induction and CDL and their heredity. Photoperiodic responses of diapause induction in the different geographical strains at different temperatures showed that diapause incidence and CDL increased with increasing latitude and decreased with increasing temperature. Similarly, diapause incidence and CDL for the hybrid strains also showed an increase with increasing latitude or decreasing temperature. Conversely, the diapause incidences were significantly lower and the CDLs were significantly shorter in hybrid strains than their parents with high diapause incidence. Furthermore, the males had significantly more influence than the females on the incidence of diapause in subsequent progeny. Diapause incidence and CDL in O. furnacalis are strikingly different among pure strains and hybrid strains. The photoperiodic response controlling diapause is strongly heritable, with diapause being a partial dominant character over nondiapause, with the incidence of diapause mainly determined by the male parent. These results can help us to predict the time course of diapause induction in nature and may provide a genetic means for pest management by providing information on the overwintering capabilities of the hybrids. [ABSTRACT FROM AUTHOR]

It is commonly observed that if the genetic divergences between parental lineages are too marked, the intermixed offspring might not be successful or might present reduced fitness, i.e., hybrid inferiority. In the present study, we performed an intraspecific hybridization using two populations of the Asian corn borer, Ostrinia furnacalis: a southern population (S) from Huizhou city (23.09°N, 114.4°E) and a northern population (N) from Harbin city (44.9°N, 127.2°E). The key life-history traits were compared between the two populations with geographical reproductive isolation and their two hybrid populations (S♀ × N♂ and N♀ × S♂ populations) at 20, 24, 28 and 32 °C. Our results showed that there were significant differences in life-history traits in the two parental populations, with the S population performing better. However, the two hybrid populations exhibited delayed larval development time, relatively reduced body weight, lower growth rate and sex ratio distortion compared with their parents. Our results provided further evidence that intraspecific hybridization between the two geographical populations reduced the fitness of the hybrids. The sexual size dimorphism was also different between the pure populations and the hybrid populations. We also found that the sex ratios in the two hybrid populations were mainly influenced by the genotype of the mothers. The negative effects of intraspecific hybridization on the key life-history traits may provide a genetic means of pest management to suppress pest populations. [ABSTRACT FROM AUTHOR]

The Western flower thrips (WFT), Frankliniella occidentalis, is a major threat to a wide range of agricultural crops and rapidly spreads throughout the world. Its international importance as a pest has led to tremendous growth in our knowledge of its biology, ecology, and novel approaches for its management. Unfortunately, the literature on WFT is widely dispersed and many researchers, extension specialists, and IPM practitioners are only now becoming aware of WFT, which has meant that management programs are still reliant on intense insecticide use, especially in recently invaded regions. Due to the current high demand in effective and sustainable control tactics for this pest, Journal of Pest Science dedicates a special issue to WFT. This special issue provides a consolidated review of WFT biology and ecology and helps to highlight alternative and novel management techniques to effectively controlling this pest in the future. [ABSTRACT FROM AUTHOR]

Liriomyza sativae and L. trifolii are highly invasive leafminer pests of vegetable crops that have invaded southern China in recent years. Liriomyza sativae was the first of these species to invade China, but it is now being displaced by L. trifolii. The rate and extent of this displacement vary across southern China. In Hainan, monocultures of highly valuable cowpea are planted and treated extensively with insecticides in attempts to control leafminer damage. In Guangdong, cowpea fields are interspersed with other less valuable crops, such as towel gourd (Luffa cylindrica), which receive significantly fewer insecticide applications than cowpea. To determine how differences in cropping systems influence the Liriomyza species composition, we conducted field trials in 2011 and 2012 in Guangdong where both species were present. We replicated conditions in Hainan by planting cowpea monocultures that were isolated from other agricultural fields, and we replicated conditions in Guangdong by planting cowpea in a mixed crop environment with towel gourd planted in neighboring plots. We then compared leafminer populations in cowpea treated with the insecticide avermectin and untreated cowpea. We also monitored leafminer populations in the untreated towel gourd. Untreated cowpea and towel gourd had comparatively low proportions of L. trifolii, which remained relatively stable over the course of each season. Avermectin applications led to increases in the proportions of L. trifolii, and after three weekly applications populations were >95% L. trifolii in both crop systems. However, the rate of change and persistence of L. trifolii in the mixed crop system were less than in the monocrop. These results indicate that L. trifolii is much less susceptible to avermectin than is L. sativae. Further, L. sativae was able to persist in the untreated towel gourd, which probably enabled it to recolonize treated cowpea. [ABSTRACT FROM AUTHOR]

Among 28 isolates of Beauveria bassiana tested for virulence against F. occidentalis in laboratory bioassays, we found strain SZ-26 as the most potent, causing 96% mortality in adults at 1×107 mL−1conidia after 4 days. The effect of the strain SZ-26 on survival, longevity and fecundity of the predatory mite Neoseiulus (Amblyseius) barkeri Hughes were studied under laboratory conditions. The bioassay results showed that the corrected mortalities were less than 4 and 8% at 10 days following inoculation of the adult and the larvae of the predator, respectively, with 1×107 conidia mL−1 of SZ-26. Furthermore, no fungal hyphae were found in dead predators. The oviposition and postoviposition durations, longevity, and fecundity displayed no significant differences after inoculation with SZ-26 using first-instar larvae of F. occidentalis as prey in comparison with untreated predator. In contrast, the preoviposition durations were significantly longer. Observations with a scanning electron microscope, revealed that many conidia were attached to the cuticles of F. occidentalis at 2 h after treatment with germ tubes oriented toward cuticle at 24 h, penetration of the insect cuticle at 36 h, and finally, fungal colonization of the whole insect body at 60 h. In contrast, we never observed penetration of the predator's cuticle and conidia were shed gradually from the body, further demonstrating that B. bassiana strain SZ-26 show high toxicity against F. occidentalis but no pathogenicity to predatory mite. [ABSTRACT FROM AUTHOR]

Insecticide resistance continues to be one of the most important issues facing agricultural production. The challenges in insecticide resistance and its management are exemplified by the situation with the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). This highly invasive pest has a great propensity for developing insecticide resistance because of its biological attributes, and cases of resistance to most classes of insecticides used for its management have been detected. To combat insecticide resistance in the western flower thrips, several insecticide resistance management (IRM) programs have been developed around the world, and these are discussed. Successful programs rely on non-insecticidal tactics, such as biological and cultural controls and host plant resistance, to reduce population pressures, rotations among insecticides of different mode of action classes to conserve insecticide efficacy, resistance monitoring, sampling to determine the need for insecticide applications and education to assure proper implementation. More judicious insecticide use is possible with the development of well-founded economic thresholds for more cropping systems. While growers will continue to rely on insecticides as part of western-flower-thrips- and thrips-transmitted virus management, more effective management of these pests will be achieved by considering their management in the context of overall integrated pest management, with IRM being a key component of those comprehensive programs. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: The spotted asparagus beetle, Crioceris quatuordecimpunctata (Coleoptera: Chrysomelidae), is one of the most devastating pests of asparagus in China. Sprayed synthetic pesticides have been used to control C. quatuordecimpunctata damage, but they pose problems because of residues and harm to natural enemies. Neither the microbial coleopteran-specific toxin from Bacillus thuringiensis tenebrionis, Cry3Aa, nor the fungal pathogen Beauveria bassiana have sufficient activity to effectively control C. quatuordecimpunctata damage to asparagus. However, second instar C. quatuordecimpunctata larvae exposed to a sublethal dose of Cry3Aa toxin demonstrated significantly higher larval mortality when exposed to B. bassiana. Our results suggest that a combination of Cry3Aa and B. bassiana may be effective in reducing damage by C. quatuordecimpunctata larvae to asparagus. [Copyright &y& Elsevier]

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is an important lepidopteran pest of cotton, Gossypium hirsutum L., in Asia. Transgenic cotton expressing the cry1Ac gene from Bacillus thuringiensis (Bt) has been widely planted for control of this pest. For managing the potential risk from resistance evolution in this pest, a new transgenic Bt cotton containing cry1Ac and cry2Ab genes (gene pyramided strategy) was designed as a successor of cry1Ac cotton. This article reports on levels of Cry2Ab tolerance in H. armigera populations from Cry1Ac cotton planting region in China based on bioassays of F1 and F2 offspring of isofemale lines. In total, 572 isofemale families of H. annigera from Xiajin County of Shandong Province (an intensive Bt cotton-planting area) and 124 families from Anci County of Hebei Province [a multiple-crop system, including corn (Zea mays L.), soybean (Gycine max (L.) Merr., peanut (Arachis spp.), and Bt cotton] were screened with both Cry1Ac- and Cry2Ab-containing diets in 2008. The bioassays results indicated that relative average development rates (BADR) of F1 full-sib families from field-collected female moths on Cry1Ac- and Cry2Ab-containing diet were positively correlated. The same correlation was found in the F2 generation, indicating cross-tolerance between Cry1Ac and Cry2Ab in field populations of H. armigera in Yellow River cotton-farming region of China. This cross-tolerance must be considered in evaluating the utility of pyramiding Bt genes in cotton for delaying evolution of resistance. [ABSTRACT FROM AUTHOR]

Simple Summary: Phthorimaea operculella is considered one of the most damaging potato pests in both field and storage. Learning the developmental performance of P. operculella on different potato varieties is necessary before developing management practices. The potato tuber moth Phthorimaea operculella Zeller is one of the most damaging potato pests in the world and is difficult to control as the larvae feed only inside potatoes. Evaluating the effects of performance of P. operculella on different potato varieties may help to facilitate the development of effective pest management practices. In our study, P. operculella reared on potato variety Lishu6 showed strong performance and on Qingshu 9 exhibited the poorest performance, while P. operculella fed on Hezuo 88 and Yunshu 304 performed moderately. Firstly, larval performance of P. operculella fed on Lishu 6 with that on Hezuo 88, Yunshu 304, and Qingshu 9 was compared by using an age-stage two-sex life table. Compared with larvae fed on Lishu 6, those fed on Qingshu 9 exhibited significantly lower survival, with only 5.56% developing to the adult stage. Secondly, the pupal weight experiment showed that the pupae weight of P. operculella feeding on Lishu 6 tubers (0.0123 g) was significantly heavier than that those feeding on Qingshu 9 (0.0102 g) (p < 0.001). Thirdly, female oviposition and larvae feeding preference indicated that females oviposited on Lishu 6 in preference to Qingshu 9 (p < 0.05, p < 0.001). Overall, this study demonstrated that Qingshu 9 is the least suitable host, and planting this variety over a large scale can provide a basis for the next step of P. operculella control. [ABSTRACT FROM AUTHOR]