Potato Beetle Research Articles

Patterns in the Formation of Isomeric Homologous Series of Epicuticular Hydrocarbons in Colorado Beetle Leptinotarsa decemlineata

Patterns in the Formation of Isomeric Homologous Series of Epicuticular Hydrocarbons in Colorado Beetle Leptinotarsa decemlineata

In Vitro Antagonistic Activity of Entomopathogenic Fungi Against Phytophthora infestans

Potato downy mildew is a disease caused by a fungus called Phytophthora infestans (Mont.) de Bary, which is mainly seen in potatoes and tomatoes, but also in other culture and wild plants belonging to the Solanaceae family. This fungus is quite important both from an economic and historical point of view. In case of an epidemic, it can cause full crop deterioration or serious losses in potatoes. Although cultural and chemical control methods are generally used in the control of the disease, there is no specific biological control method in this regard. Entomopathogenic fungi (EPFs) are generally used as biological control agents in the control of insect pests. Recently, there are many studies showed that these fungi can live endophytically on various cultivated plants and provide beneficial properties to the plants they live with. In this study, it was aimed to determine the in vitro antagonistic activities of different entomopathogenic fungi previously isolated from potato fields and identified by molecular methods against P. infestans. Earlier work determined that these fungi had a lethal effect on Leptinotarsa decemlineata (Say, 1824). Antagonistic activity tests were performed according to the "direct opposition method" and percentage (%) activity values were calculated. As a result of the tests, the most effective isolates were found to be Beauveria sp. SK-14 (75.23%) and Metarhizium sp. SK-24 (76.23%). It is thought that the results obtained will contribute to the biocontrol of diseases and pests in potatoes.

Transgenerational sublethal pyrethroid exposure gives rise to insecticide resistance in a pest insect

The evolution of insecticide resistance has been attributed to strong directional selection by lethal concentrations of insecticides, but there is growing evidence that sublethal doses may also modify resistance through the hormetic effects. Hormesis is a beneficial effect caused by exposure to low doses. However, the role of parental (transgenerational) effects on hormesis, and through that on insecticide resistance, is still unclear. We investigated the effects of several sublethal pyrethroid insecticide (Decis) doses on survival, body mass, and reproduction within four generations (F0, F1, F2, and F3) of the Colorado potato beetle (Leptinotarsa decemlineata). We found that insecticide exposure had mostly linear adverse within-generation effects: decreased larva-to-adult survival, adult body mass, and egg hatching. However, transgenerational exposure led to hormetic effects: increased larva-to-adult survival and pre-diapause adult body mass. Moreover, transgenerational effects were even more positive for offspring exposed to insecticides, leading to decreased larva-to-adult survival, increased body mass, and egg hatching. Our results show that despite mostly negative within-generation effects, transgenerational sublethal exposure to insecticide can cause unwanted positive hormetic effects in their offspring, making them to resist or tolerate the insecticides better, even though the underlying mechanisms are still unclear.

Illustration Of Polyfunctional Properties of Insecticidal Strains Of Bacillus Thuringiensis

In this study, several economically efficient nutrient media based on local raw materials were selected. Phytohormone synthesis, biomass production, insecticidal activity against the Colorado beetle and effects on plant growth and development in vegetative experiments of Bacillus thuringiensis strains grown in these nutrients were studied. Bacterial strains of Bacillus thuringiensis grown on molasses medium showed the highest insecticidal activity, entomocidal activity was 31.4% on 7 days and 67.4% on 14 days. The average entomocidal activity of B. thuringiensis bacterial strains grown on nonfat dry milk-based medium was 34.5% against the Colorado beetle after 7 days of incubation, and 67.7% by day 14. According to the results of the experiment, it is possible to recommend nutrient media based on molasses and dry milk for the production of biopreparations based on Bacillus thuringiensis bacterial strains.

Fungicides modify pest insect fitness depending on their genotype and population

Fungicides are the most sold pesticide group, with an 8% increase in sales in Europe within the last decade. While adverse short-term fungicide effects on non-target insect species have been reported, the long-term effects and their impact on fitness are unclear. As the effects may depend on both the fungicide and the genetic background of the species, we investigated the effects of the commonly used fungicide, fluazinam, on the Colorado potato beetle's life history traits, and whether the effects were dependent on a previously characterized insecticide resistance mutation (S291G in acetylcholinesterase-2 gene) in different populations. Our findings show that fungicide exposure can have both negative and positive, long-lasting effects on beetles, depending on the parental insecticide resistance status and population. In the Belchow population, individuals carrying resistance mutation had higher survival, but they produced offspring with lower egg-hatching rates. While, in the Vermont population, fungicide exposure increased the body mass and offspring quality in the beetles carrying resistance mutation but did not affect the beetles’ survival. Our results suggest that commonly used fungicides can have both negative and positive effects on pest insects’ life-history, however, their impact may differ depending on the population and parental genetic background.

Transposable elements differ between geographic populations of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae).

Agricultural insect herbivores show a remarkable ability to adapt to modern agroecosystems, making them ideal for the study of the mechanisms underlying rapid evolution. The mobilization of transposable elements is one mechanism that may help explain this ability. The Colorado potato beetle, Leptinotarsa decemlineata, is a highly adaptable species, as shown by its wide host range, broad geographic distribution, and tolerance to insecticides. However, beetle populations vary in insecticide tolerance, with Eastern US beetle populations being more adaptable than Western US ones. Here, we use a community ecology approach to examine how the abundance and diversity of transposable elements differs in 88 resequenced genomes of L. decemlineata collected throughout North America. We tested if assemblages and mobilization of transposable elements differed between populations of L. decemlineata based on the beetle's geography, host plant, and neonicotinoid insecticide resistance. Among populations of North American L. decemlineata, individuals collected in Mexico host more transposable elements than individuals collected in the United States. Transposable element insertion locations differ among geographic populations, reflecting the evolutionary history of this species. Total transposable element diversity between L. decemlineata individuals is enough to distinguish between populations, with more TEs found in beetles collected in Mexico than in the United States. Transposable element diversity does not appear to differ between beetles found on different host plants, or relate to different levels of insecticide resistance.

Tetraose steroidal glycoalkaloids from potato provide resistance against Alternaria solani and Colorado potato beetle.

Plants with innate disease and pest resistance can contribute to more sustainable agriculture. Natural defence compounds produced by plants have the potential to provide a general protective effect against pathogens and pests, but they are not a primary target in resistance breeding. Here, we identified a wild relative of potato, Solanum commersonii, that provides us with unique insight in the role of glycoalkaloids in plant immunity. We cloned two atypical resistance genes that provide resistance to Alternaria solani and Colorado potato beetle through the production of tetraose steroidal glycoalkaloids (SGA). Moreover, we provide in vitro evidence to show that these compounds have potential against a range of different (potato pathogenic) fungi. This research links structural variation in SGAs to resistance against potato diseases and pests. Further research on the biosynthesis of plant defence compounds in different tissues, their toxicity, and the mechanisms for detoxification, can aid the effective use of such compounds to improve sustainability of our food production.

Tetraose steroidal glycoalkaloids from potato provide resistance against Alternaria solani and Colorado potato beetle

Plants with innate disease and pest resistance can contribute to more sustainable agriculture. Natural defence compounds produced by plants have the potential to provide a general protective effect against pathogens and pests, but they are not a primary target in resistance breeding. Here, we identified a wild relative of potato, Solanum commersonii, that provides us with unique insight in the role of glycoalkaloids in plant immunity. We cloned two atypical resistance genes that provide resistance to Alternaria solani and Colorado potato beetle through the production of tetraose steroidal glycoalkaloids (SGA). Moreover, we provide in vitro evidence to show that these compounds have potential against a range of different (potato pathogenic) fungi. This research links structural variation in SGAs to resistance against potato diseases and pests. Further research on the biosynthesis of plant defence compounds in different tissues, their toxicity, and the mechanisms for detoxification, can aid the effective use of such compounds to improve sustainability of our food production.

Identification of chitinase genes and roles in the larval-pupal transition of Leptinotarsa decemlineata.

Insect chitinases play crucial roles in degrading chitin in the extracellular matrix, affecting insect development and molting. However, our understanding of the specific functions of various chitinases in Leptinotarsa decemlineata is limited, hindering the deployment of novel gene-targeting technologies as pest management strategies. We identified and characterized 19 full-length complementary DNA (cDNA) sequences of chitinase genes (LdChts) in Leptinotarsa decemlineata. Despite having varying domain architectures, all these chitinases contained at least one chitinase catalytic domain. Phylogenetic analysis classified the chitinase proteins into ten distinct clusters (groups I-X). Expression profiles showed the highest expression in chitin-rich tissues or during specific developmental stages from the larva-to-pupa transition. Gene-specific RNA interference (RNAi) experiments provided valuable insight into chitinase gene function. Silencing of group II LdCht10 prevented larval-larval molting, larval-prepupal, and prepupal-pupal processes. Moreover, our study revealed that LdCht5, LdCht2, LdCht11, LdCht1, and LdCht3 from groups I and VII-X were specifically essential for the transition from prepupal to pupal stage, whereas LdIDGF2 from group V was necessary for the larval-prepupal metamorphic process. The chitinase gene LdCht7 from group III and LdIDGF4 from group V were involved in both the larva-to-prepupa and the prepupa-to-pupa shift. Additionally, our findings also shed light on the exclusive expression of nine chitinase genes within group IV in the digestive system, suggesting their potential role in regulating larval body weight and larva-to-pupa transition. Our results provide a comprehensive understanding of the functional specialization of chitinase genes during the molting process of various stages and identify potential targets for RNAi-based management of Leptinotarsa decemlineata. © 2023 Society of Chemical Industry.

Engineering of insecticidal hybrid gene into potato chloroplast genome exhibits promising control of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae).

The potato chloroplast was transformed with codon optimized synthetic hybrid cry gene (SN19) to mitigate crop losses by Colorado potato beetle (CPB). The bombarded explants (leaves and internode) were cultured on MS medium supplemented with BAP (2.0mg/l), NAA (0.2mg/l), TDZ (2.0mg/l) and GA3 (0.1mg/l); spectinomycin 50mg/l was used as a selection agent in the medium. Leaf explants of cultivar Kuroda induced highest percentage (92%) of callus where cultivar Santae produced the highest percentage (85.7%) of transplastomic shoots. Sante and Challenger showed 9.6% shoot regeneration efficiency followed by cultivar Simply Red (8.8%). PCR amplification yielded 16 postive transplastomic plantlets out of 21 spectinomycin resistant ones. Target gene integration was confirmed by PCR and Southern blot, whereas RT-qPCR was used to assess the expression level of transgene. The localization of visual marker gene gfp was tracked by laser scanning confocal microscopy which confirmed its expression in chloroplasts of leaf cells. The transplastomic plants ensured high mortality to both larvae and adult CPB. Foliage consumption and weight gain of CPB fed on transplastomic leaves were lower compared to the control plants. Sucessful implementation of current research findings can lead to a viable solution to CPB mediated potato losses globally.

Population development of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae), under individually- and group-reared conditions

The Colorado potato beetle (CPB) is a serious pest of potato in China. To determine the effect of individual-rearing and group-rearing on its population growth and development, we studied its life tables and projected its population growth using the TWOSEX-MS Chart and TIMING-MS Char programs. Results showed that individually-reared CPBs were significantly better than that of group-reared CPBs, in terms of intrinsic rate of increase (0.07), finite rate of increase (1.07), net reproductive rate (39.93), and gross reproductive rate (221.23) compared to that of group-reared treatment (0.05; 1.05; 10.84; and 58.77). Additionally, individually-reared CPB populations had faster development, characterized by shorter generation cycles, and higher female survival rates, which produced more offspring per unit time, compared to the group-reared CPB population. However, in potato fields, the CPB are mostly found in groups and therefore the group-rearing method should be more effective for prediction and possible management of CPB populations. This study serves as a reference for an effective and biological prevention and control of the CPBs.

Evaluation of the phenotypic polymorphism of the pattern of Leptinotarsa decemlineata Say pronotum in the conditions of Kamianka-Buzka city (Lviv Oblast)

Aim. The Colorado potato beetle population is characterized by a high degree of polymorphism. This provides a high level of adaptability to the most diverse distribution conditions. The aim is to the study of the variability of the pattern of Leptinotarsa decemlineata pronotum in June 2021 and June 2022. Methods. The analysis of the phenotypic variability of L. decemlineata population of Kamianka-Buzka city based on studying the presence or absence of certain phens, their number and placement according to Tauer method. Results. 22 variations of phens belonging to A, B, C, D, E, G, K, L, M, P groups were found. The dominant were phens of A, B, C, D, E, F groups. The most variable were the phens of A and E groups. The phenotypic structure of the colorado beetle population was determined according to Kohmaniuk’s classification. It was found that the dominant morphs in 2021 and 2022 were U (42 % and 27 %), UP (13 % and 18 %) and V (23 % and 21 %), respectively. Conclusions. The analysis of the frequency of phenoforms according to the Fasulati method showed that in the population of 2021 and 2022, phenoforms 3, 6 and 9 were dominant. They form the basis of the population and ensure the resistance of the population to the insecticides. The study of the intrapopulation diversity indicates an unbalanced population structure of L. decemlineata.

Network Modeling for Post-Entry Management of Invasive Pest Species in the Philippines: The Case of the Colorado Potato Beetle, Leptinotarsa decemlineata (Say, 1824) (Coleoptera: Chrysomelidae).

Crop shifting is considered as an important strategy to secure future food supply in the face of climate change. However, use of this adaptation strategy needs to consider the risk posed by changes in the geographic range of pests that feed on selected crops. Failure to account for this threat can lead to disastrous results. Models can be used to give insights on how best to manage these risks. In this paper, the socioecological process graph technique is used to develop a network model of interactions among crops, invasive pests, and biological control agents. The model is applied to a prospective analysis of the potential entry of the Colorado potato beetle into the Philippines just as efforts are being made to scale up potato cultivation as a food security measure. The modeling scenarios indicate the existence of alternative viable pest control strategies based on the use of biological control agents. Insights drawn from the model can be used as the basis to ecologically engineer agricultural systems that are resistant to pests.

On the successful acclimatization of the Colorado potato beetle Leptinotarsa decemlineata (Say, 1824) (Coleoptera: Chrysomelidae) in Primorsky kray

The successful naturalization of the Colorado potato beetle in Primorsky Kray is limited by the monsoon climate, namely unstable fluctuating weather conditions with periodic catastrophic precipitation. The most of potato fields are located in the bottomlands of rivers or in close proximity to water bodies and a drastic increase in the runoff due to excessive simultaneous rainfall leads to the flooding of agricultural lands and the elimination of the fodder plants. The Colorado potato beetle is an oligophage and can not switch to alternative food sources during these periods. Moreover, beetles that enter diapause under these conditions die because of flooding and cold injury. Despite this fact, the pest remains a threat to the potato production in the region and can cause significant damage in case of repeated invasions during periods with more favorable conditions.

RESISTANCE OF PROMISING POTATO VARIETIES TO THE MOST IMPORTANT BEETLE PESTS IN THE CONDITIONS OF THE NORTHWEST OF THE EUROPEAN PART OF RUSSIA AND THE SOUTH OF THE FAR EAST

The article provides the results of evaluation of 10 promising potato varieties for the group resistance to the Colorado potato beetle Leptinotarsa decemlineata Say and to the Potato ladybird Henosepilachna vigintiomaculata Motsch. The researches were performed by field methods with artificial colonization of plants of the studied varieties in 1st instar, in the quantity of 30–100 larvae for each potato variety, and were held: according to the Colorado beetle – on experimental field of the All-Russian Research Institute for Plant Protection (Saint-Petersburg – Pushkin); according to the potato ladybird – on experimental field of the Federal Scientific Center of Agricultural Biotechnology of the Far East named after A.K. Chaikа (Primorsky Krai, Ussuriysk). Examples of potato varieties from the new assortment confirm the significant similarity (parallelism of developing) of the trophic reactions of both species, which have the same type of nutrition and many similar features of development biology. As the first result, it has shown that the Severnyi and Smak varieties have a group resistance to both phytophages with a survival of 10–20% of larvae before pupation. In other side, the Avgustin and Dalnevostochnyi varieties noted as a favourable for the development of these pests with a survival of 45–75% of larvae.

Synthesis of Novel Carboxamide Derivatives: Insecticidal Activity, Acetylcholinesterase Activity and In Silico Calculations

The insecticidal activity of carboxamide derivatives was investigated against both larvae and adults of Myzus percisace (Sulzer) (Hemiptera: Aphididae), Leptinotarsa decemlineata (Coleoptera: Chrysomelidae), and Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) in different concentrations. The synthesized compounds were obtained good yield, and their molecular structures were confirmed by FTIR, NMR, and MALDI-TOF/MS. The compound 3o was found to be the most active against Leptinotarsa decemlineata adults, while the compound 3l was found against larvae. Furthermore, the compounds were evaluated against acetylcholinesterase (AChE) enzyme, and two of the compounds (3n and 3o) showed moderate inhibitory effect against both commercial acetylcholinesterase (0.18 ± 0.01 and 0.13 ± 0.01 μM) and M. percisace adult homogenate (0.65 ± 0.02 and 0.24 ± 0.01 μM), respectively. In silico molecular docking and ADME properties were performed.

Does Leptinotarsa decemlineata larval survival after pesticide treatment depend on microbiome composition?

The microbiomes of some arthropods are believed to eliminate pesticides by chemical degradation or stimulation of the host immune system. The Colorado potato beetle (CPB; Leptinotarsa decemlineata) is an important agricultural pest with known resistance to used pesticides. We sought to analyze microbiome composition in CPB larvae from different sites and to identify the effect of pesticides on the microbiome of surviving and dead larvae after chlorpyrifos treatment in laboratory. Changes in Lactococcus lactis community in larvae treated with chlorpyrifos and fed by potato leaves with L. lactis cover were studied in manipulative experiment. The microbiome was characterized by sequencing the 16S RNA gene. The microbiome of L. decemlineata larvae is composed of a few operational taxonomic units (OTUs) (Enterobacteriaceae, Pseudocitrobacter, Acinetobacter, Pseudomonas, L. lactis, Enterococcus, Burkholderia, and Spiroplasma leptinotarsae). The microbiome varied among the samples from eight sites and showed differences in profiles between surviving and dead larvae. The survival of larvae after chlorpyrifos treatment was correlated with a higher proportion of L. lactis sequences in the microbiome. The S. leptinotarsa profile also increased in the survived larvae, but this OTU was not present in all sampling sites. In manipulative experiments, larvae treated with L. lactis had 5-fold lower mortality rates than untreated larvae. These results indicate that the microbiome of larvae is formed from a few bacterial taxa depending on the sampling site. A member of the gut microbiome, L. lactis, is believed to help overcome the toxic effects of chlorpyrifos in the larval gut. This article is protected by copyright. All rights reserved.

Effects of passages through an insect or a plant on virulence and physiological properties of the fungus Metarhizium robertsii.

Species of the genus Metarhizium are characterized by a multitrophic lifestyle of being arthropod parasites, rhizosphere colonizers, endophytes, and saprophytes. The process of adaptation to various organisms and substrates may lead to specific physiological alterations that can be elucidated by passaging through different hosts. Changes in virulence and cultivation properties of entomopathogenic fungi subcultured on different media or passaged through a live insect host are well known. Nevertheless, comparative in-depth physiological studies on fungi after passaging through insect or plant organisms are scarce. Here, virulence, plant colonization, hydrolytic enzymatic activities, toxin production, and antimicrobial action were compared between stable (nondegenerative) parent strain Metarhizium robertsii MB-1 and its reisolates obtained after eight passages through Galleria mellonella larvae or Solanum lycopersicum or after subculturing on the Sabouraud medium. The passaging through the insect caused similar physiological alterations relative to the plant-based passaging: elevation of destruxin A, B, and E production, a decrease in protease and lipase activities, and lowering of virulence toward G. mellonella and Leptinotarsa decemlineata as compared to the parent strain. The reisolates passaged through the insect or plant showed a slight trend toward increased tomato colonization and enhanced antagonistic action on tomato-associated bacterium Bacillus pumilus as compared to the parental strain. Meanwhile, the subculturing of MB-1 on the Sabouraud medium showed stability of the studied parameters, with minimal alterations relative to the parental strain. We propose that the fungal virulence factors are reprioritized during adaptation of M. robertsii to insects, plants, and media.

The interaction of nicotinic acetylcholine receptor subunits Ldα3, Ldα8 and Ldβ1 with neonicotinoids in Colorado potato beetle, Leptinotarsa decemlineata

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an extremely destructive notifiable quarantine pest. Over the last two decades, neonicotinoid insecticides, particularly thiamethoxam and imidacloprid, have been used to control it in Xinjiang, and local field populations have developed different levels of resistance in consequence. However, the contributions of nicotinic acetylcholine receptors (nAChRs) to neonicotinoid resistance are currently poorly understood in CPB. Previous studies have shown that nAChRα1, α3, α8 and β1 are major target subunits for neonicotinoids in some model and important agricultural insects including nAChRα1 subunit of L. decemlineata (Ldα1). In this study, the expression levels of Ldα3, Ldα8 and Ldβ1 following 72 h of treatments with median lethal doses of thiamethoxam and imidacloprid were compared using real-time quantitative PCR. These genes were then individually and simultaneously knocked down with Ldα1 by RNA interference (RNAi) using a double-stranded RNA (dsRNA) feeding method for six days to explore their roles in CPB susceptibility to imidacloprid and thiamethoxam. The results showed that the expressions of Ldα3, Ldα8 and Ldβ1 were significantly decreased by 36.99–74.89% after thiamethoxam and imidacloprid treatments, compared with the control. The significant downregulation of the target genes resulting from RNAi significantly reduced the mortality of adults exposed to thiamethoxam and imidacloprid by 34.53% –56.44% and 28.78%–43.93%, respectively. Furthermore, the adult survival rates were not affected by every dsRNA-feeding treatment, while the body weight of the test adults significantly deceased after four and six days of individual gene RNAi. This study showed that Ldα3, Ldα8 and Ldβ1 are down-regulated by thiamethoxam and imidacloprid and play important roles in the tolerance of CPB to neonicotinoids.

Inefficient uptake of small interfering RNAs is responsible for their inability to trigger RNA interference in Colorado potato beetle cells.

There has been limited success in the usage of exogenous small interference RNA (siRNA) or small hairpin RNA (shRNA) to trigger RNA interference (RNAi) in insects. Instead, long double-stranded RNAs (dsRNA) are used to induce knockdown of target genes in insects. Here, we compared the potency of si/sh RNAs and dsRNA in Colorado potato beetle (CPB) cells. CPB cells showed highly efficient RNAi response to dsRNA. However, si/sh RNAs were inefficient in triggering RNAi in CPB cells. Confocal microscopy observations of Cy3 labeled-si/sh RNA cellular uptake revealed reduced si/sh RNA uptake compared to dsRNA. si/sh RNAs were stable in the conditioned media of CPB cells. Although in a small amount, when internalized by CPB cells, the si/sh RNAs were processed by the Dicer enzyme. Lipid-mediated transfection and chimeric dsRNA approaches were used to improve the delivery of si/sh RNAs. Our results suggest that the uptake of si/sh RNAs is inefficient in CPB cells, resulting in ineffective RNAi response. However, with the help of effective delivery methods, si/sh RNA could be a useful option for developing target-specific RNAi-mediated biopesticides.