Colorado Potato Beetle Populations Research Articles

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.

Impact of water stress on the demographic traits and population projection of Colorado potato beetle.

Introduction: The Colorado potato beetle is one of the famous quarantine pests in China which is extremely destructive to Solanaceae crops and causes serious losses to the potato industry. Methods: In this experiment, the host plant potato was subjected to different degrees of water stress to observe the oviposition selection, growth and development, survival, reproduction and population growth of Colorado potato beetles. Results: The results showed that adult Colorado potato beetles laid more eggs on potato plants suitable for water treatment, but fewer eggs on potato plants treated with water stress. The developmental duration of Colorado potato beetles in light drought treatment was shorter than that in control treatment, and the survival rate was higher than that in control treatment. With the aggravation of water stress, the developmental duration was prolonged, survival rate was decreased, and the number of eggs was decreased. Under different water stress levels, the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R 0), and mean generation time (T) of the Colorado potato beetle population were significantly lower than those of control treatment, but there was no significant difference between light drought and control treatment. The TIMING-MS Chart program was used to predict the population dynamics of Colorado potato beetle for 110days, which showed the fastest population growth in CK treatments and the slowest in HD treatments. The reduced water content of the leaves also reduces the survival rate of adult Colorado potato beetles. The growth, development, survival, and reproduction of Colorado potato beetles are affected by water stress of host plants. Moderate and heavy droughts have negative effects on the development and reproduction of Colorado potato beetles. Discussion: This information can be used to clarify the impact of water stress on the growth, development and population dynamics of Colorado potato beetle, to provide a theoretical basis for the control of this pest.

Regional differences in susceptibility to spinosyn insecticides registered for Colorado potato beetle management in Canada

The Colorado potato beetle (CPB) is the most economically important pest of Canadian potato, and if left uncontrolled, it can completely consume the crop. In the past decade, the control of CPB has relied heavily on systemic insecticides, principally the neonicotinoids thiamethoxam and clothianidin. Resistance to neonicotinoids in CPB has been well documented in the past 2 decades and mechanisms underlying the resistance better understood. In contrast, resistance to other insecticide classes, including spinosyns (spinosad and spinetoram) and anthranillic diamides (chlorantraniliprole and cyantraniliprole), have not been studied to the same degree in CPB. Spinosyns are the only insecticide certified for organic potato growers in Canada and are frequently applied as a mid-season foliar spray by conventional growers when seed treatments with neoniconitoid or diamide experience control breaks. Improved knowledge on resistance to spinosyns in CPB would allow for the development of regional management strategies. A survey of insecticide susceptibility in CPB populations from 6 potato growing regions between 2018 and 2022 observed: 1) spatial and temporal resistance trends; 2) cross-resistance; and 3) evidence of regional differences in susceptibility to spinosyns. The proportion of populations within each province considered resistant to spinosyns was, in descending order: Québec (16%) > Ontario (14%) > Manitoba (13%) > New Brunswick (9%) > Prince Edward Island (2%) > Alberta (0%). There was a significant change in CPB mortality at the diagnostic concentration (DC = LC90) for spinosad and spinetoram in the 6 provinces but only for year 5 relative to the previous 4 years. Moderate cross-resistance was determined between spinosad and spinetoram with the DC mortality for all populations based on a positive and significant correlation (adjusted R2 = 0.3758; P = 1.263e−13). There was also a positive relationship observed between the number of spinosyn applications (years applied at the sampling location) and declining susceptibility to spinosad (R2 = 0.0927; P < 0.002). Cross-resistance was observed between spinosyns and insecticides in the other two classes, the more significant correlation was between spinosad and tetraniliprole (R2 = 0.3025; P < 0.0002). In Québec, the greater spinosad use in organic potato farms led to resistance in those CPB populations, but spinosyn resistance at conventional farms was not related to greater application of neonicotinoids and diamides. Spinosyns remain relatively effective, nevertheless growers should be concerned over the increasing cases of reduced susceptibility in conventional potato farms and resistance where organic production occurs. Resistance management should continue to encourage rotation with products from the other classes in season and between years in order to extend spinosyn use for CPB control.

Effects of Low Doses of a Novel dsRNA-based Biopesticide (Calantha) on the Colorado Potato Beetle.

The Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) is a destructive pest of the cultivated potato, Solanum tuberosum. Members of this species are well-suited to agricultural habitats because of a suite of physiological adaptations and their ability to evolve resistance to multiple insecticides. Recently, a novel double-stranded RNA (dsRNA) insecticide (Calantha, active ingredient ledprona) has been demonstrated as an effective tool to manage Colorado potato beetle populations through RNA interference (RNAi). Previous studies have demonstrated the lethality of the high doses of ledprona but had not assessed possible effects of low doses that may happen due to product degradation in the environment, incomplete spray coverage, and foliage growth. Exposure of fourth instar larvae to low concentrations of ledprona interfered with their pupation. Exposure of adults significantly reduced their mobility after seven days, as well as their fertility. Reproductive effects were stronger in females, especially when exposed before reaching sexual maturity. The observed effects of low doses of ledprona may aid in the overall management of Colorado potato beetles by reducing the size of resident populations, inhibiting beetle movement within and between fields, and reducing the population growth rate.

Use of pathogenic microorganisms in the control of the Colorado potato beetle (Leptinotarsa decemlineata Say.)

The focus of this article is the comprehensive study of the Colorado potato beetle population within potato agro-biocenosis. The research delves into the intricate processes that contribute to the formation and bioecological characteristics of this beetle population. The article also delves into a specific strain known as Beauveria bassiana VTq-28, which was isolated from the Colorado potato beetle. This strain was subjected to testing both in laboratory settings and in the field, targeting various developmental stages of the Colorado potato beetle. The objective was to evaluate the effectiveness of Beauveria bassiana VTq-28 as a biocontrol agent against the beetle. Additionally, the research assessed the insecticidal activity of locally sourced strains of B. thuringiensis against the Colorado potato beetle. This analysis provides insights into the potential of B. thuringiensis strains as another avenue for biocontrol. By thoroughly examining the population dynamics, bioecological characteristics, and the potential of specific microbial agents for controlling the Colorado potato beetle, this study contributes to the understanding of pest management strategies within potato agro-biocenosis. The findings have implications for sustainable agricultural practices and the effective control of this economically significant pest.

Evidence of hard-selective sweeps suggests independent adaptation to insecticides in Colorado potato beetle (Coleoptera: Chrysomelidae) populations.

Pesticide resistance provides one of the best examples of rapid evolution to environmental change. The Colorado potato beetle (CPB) has a long and noteworthy history as a super-pest due to its ability to repeatedly develop resistance to novel insecticides and rapidly expand its geographic and host plant range. Here, we investigate regional differences in demography, recombination, and selection using whole-genome resequencing data from two highly resistant CPB populations in the United States (Hancock, Wisconsin and Long Island, New York). Demographic reconstruction corroborates historical records for a single pest origin during the colonization of the Midwestern and Eastern United States in the mid- to late-19th century and suggests that the effective population size might be higher in Long Island, NY than Hancock, WI despite contemporary potato acreage of Wisconsin being far greater. Population-based recombination maps show similar background recombination rates between these populations, as well as overlapping regions of low recombination that intersect with important metabolic detoxification genes. In both populations, we find compelling evidence for hard selective sweeps linked to insecticide resistance with multiple sweeps involving genes associated with xenobiotic metabolism, stress response, and defensive chemistry. Notably, only two candidate insecticide resistance genes are shared among both populations, but both appear to be independent hard selective sweep events. This suggests that repeated, rapid, and independent evolution of genes may underlie CPB's pest status among geographically distinct populations.

Assessing the Population Structure of Colorado Potato Beetle Populations in Croatia Using Genetic and Geometric Morphometric Tools

The Colorado potato beetle (CPB, Leptinotarsa decemlineata Say) is one of the most successful invasive species worldwide. It has been present in Croatia since 1947, where it has caused significant damage to potato plants and developed resistance to several insecticides. Our study is the first attempt to investigate the population structure of CPBs in Croatia. SNP and GM techniques provided us with data about the population structure of the CPB population. A Bayesian model-based clustering algorithm implemented in STRUCTURE, principal component analysis (PCA), and discriminant analysis of principal components (DAPC) were used to analyze the genetic structure of CPBs. For the morphometric analysis, the hindwing shape of the same CPB individuals was examined using wing venation patterns. We detected the low genetic and phenotypic variabilities of CPB populations and the presence of a single panmictic population in the study area, well adapted to different environmental conditions, indicating high phenotypic plasticity. Due to such exceptional adaptation of the CPB population, it is necessary to implement an area-wide approach in future pest control management.

Toxicity of a novel dsRNA-based insecticide to the Colorado potato beetle in laboratory and field trials.

The Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) is one of the most notorious pests of the potato, Solanum tuberosum. Potato beetles are capable of developing resistance to various insecticides in relatively few generations. Novel and effective means of controlling Colorado potato beetle populations are constantly required to protect potato crops and prevent loss of yield. The knockdown of gene function through ribonucleic acid interference has been demonstrated in Colorado potato beetles, suggesting the use of this technology as a means of beetle management. A novel double-stranded RNA-based insecticide with the active ingredient, ledprona, has been tested in variable dose laboratory bioassays, followed by field studies. Exposure to ledprona resulted in both increased beetle mortality and decreased foliage consumption in all four instars and adult beetles. Effects decreased from earlier to later life stages. No ovicidal activity was detected. Onset of mortality was slower compared with existing chemical insecticides. Nevertheless, field applications of formulated ledprona to potato plots resulted in their protection comparable with that provided by spinosad and chlorantraniliprole. Based on the results of this study, formulated ledprona has attributes to become a useful tool in controlling Colorado potato beetle populations that is likely to be a good fit in integrated pest management protocols. © 2022 Society of Chemical Industry.

Genome Resequencing Reveals Rapid, Repeated Evolution in the Colorado Potato Beetle

Insecticide resistance and rapid pest evolution threatens food security and the development of sustainable agricultural practices, yet the evolutionary mechanisms that allow pests to rapidly adapt to control tactics remains unclear. Here, we examine how a global super-pest, the Colorado potato beetle (CPB), Leptinotarsa decemlineata, rapidly evolves resistance to insecticides. Using whole-genome resequencing and transcriptomic data focused on its ancestral and pest range in North America, we assess evidence for three, nonmutually exclusive models of rapid evolution: pervasive selection on novel mutations, rapid regulatory evolution, and repeated selection on standing genetic variation. Population genomic analysis demonstrates that CPB is geographically structured, even among recently established pest populations. Pest populations exhibit similar levels of nucleotide diversity, relative to nonpest populations, and show evidence of recent expansion. Genome scans provide clear signatures of repeated adaptation across CPB populations, with especially strong evidence of selection on insecticide resistance genes in different populations. Analyses of gene expression show that constitutive upregulation of candidate insecticide resistance genes drives distinctive population patterns. CPB evolves insecticide resistance repeatedly across agricultural regions, leveraging similar genetic pathways but different genes, demonstrating a polygenic trait architecture for insecticide resistance that can evolve from standing genetic variation. Despite expectations, we do not find support for strong selection on novel mutations, or rapid evolution from selection on regulatory genes. These results suggest that integrated pest management practices must mitigate the evolution of polygenic resistance phenotypes among local pest populations, in order to maintain the efficacy and sustainability of novel control techniques.

Population structure and pattern of geographic differentiation of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) in Turkey.

The Colorado potato beetle (CPB) is the most harmful pest of potato in potato cultivation regions globally. Although it is an economically important agricultural pest, the population structure and colonization route of this species in Turkey are uncertain. We used microsatellite and mitochondrial DNA (mtDNA) markers to obtain information about the population source, structure and bio-invasion route of CPB populations in Turkey. The common single mtDNA haplotype in European CPB populations was obtained in all Turkish CPB populations based on mtDNA data analysis. However, microsatellites revealed a low level of genetic variation in CPB populations. The results of microsatellite analysis [factorial correspondence analysis (FCA), Bayesian analysis of genetic population structure (BAPS), unweighted pair group method with arithmetic mean (UPGMA) dendrogram, F-statistics and Nei's distances] indicated three groups for invasive CPB: Thrace-Marmara and Aegean; Black Sea, Central Anatolia and Mediterranean; Northeastern Anatolia. Region-specific alleles have been identified in regions, where commercial potato cultivation and insecticide use are intensive. The detection of a single fixed European haplotype in all Turkish populations has proved that CPB in Turkey originated from Europe as a result of a founder event occurred in European populations. Low genetic variation was due to the short time period since the spread of CPB from America to Europe. The highest number of private alleles were found in the top commercial potato cultivation region-Central Anatolia from where the CPB populations spread to other parts of Turkey. © 2021 Society of Chemical Industry.

Stacked insecticidal genes in potatoes exhibit enhanced toxicity against Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

The present study was performed to express stacked insecticidal genes in potato cv. Lady Olympia and Agria to encode resistance against Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say). Bacillus thuringiensis (Bt) gene (cry3A), synthetic hybrid (SN-19) and plant proteinase inhibitor Oryza cystatin II (OCII) cloned in pCAMBIA1301 binary vector in two different combinations as of DS-1 (cry3A + SN-19 genes) and DS-2 (OCII + SN-19 genes) constructs and further transformed to two potato cultivars using Agrobacterium-mediated transformation. All molecular analyses confirmed gene integration and expression in a total of 27 primary transformants in both Agria and Lady Olympia. Insecticidal effects of T0 progeny transgenic potato plants were tested against CPB under laboratory conditions. Transgenic plants of Agria and Lady Olympia transformed with DS-1 and DS-2 constructs caused 100% mortality to all larval stages and adults of CPB. However, 100% mortality of tested insects took a longer time in the adult stage (10–14 days) compared to larval stages (2–6 days). Foliage consumption by L2-L4 larval stages and adults of CPB was significantly reduced in Agria and Lady Olympia plants transformed with DS-1 and DS-2 constructs, as compared to their control plants. Lower foliage consumption of transgenic plants by L1 larval stages was also observed, but the reduction was only statistically significant for some of the tested plants. These promising results indicate that the transgenic potato plants exhibit a high potential in controlling CPB population and are a useful tool in the management of imidacloprid-resistant CPB.

Efficacy of indigenous isolates of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycota: Hyphomycetes) against the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)

BackgroundThe Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is one of the most damaging pests of potatoes all over the world as well as in Turkey. Both adults and larvae of this pest feed on the foliage of potatoes, and often cause complete defoliation of potato plants, with considerable yield losses of up to 60%. Chemical control of this pest has induced the selection of resistant CPB populations and negative environmental impact. The aim of the present study was to evaluate the pathogenicity of 14 Turkish isolates of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycota: Hyphomycetes) against different stages of CPB under laboratory conditions.ResultsAll isolates were tested as conidial suspensions of (1 × 107 conidia/ml), using spray method. The results from pathogenicity assays showed that virulence of tested isolates was variable, and mortality increased with the time of exposure. The highest mortality was seen in larvae of CPB; however, young larvae (1st and 2nd instars) were more susceptible to fungal isolates than older ones (3rd and 4th instars). Four isolates (BbDm-1, BbDs-2, BbMg-2, and BbMp-1) were more pathogenic than others against L. decemlineata, causing mortalities between 96.7 and 100% in the 2 youngest larval instars, respectively, between 91.7 and 96.7% in the 2 oldest larval instars, respectively, and between 93.3 and 96.7% in 0–48-h-old adults, respectively, 9 days post treatment. Furthermore, these 4 isolates had the most potent egg-hatching inhibitory effects (66.7–90%). The results of molecular phylogenetic analyses based on the ITS region sequence indicated that all tested B. bassiana isolates showed a high similarity (99%) with other B. bassiana isolates in GenBank.ConclusionsResults suggested that the 4 B. bassiana isolates were highly virulence and had the potential for biological control of CPB. Further tests under field conditions are recommended to validate the laboratory results.

Effects of insecticides and synergistic chemicals on the efficacy of the entomopathogenic nematode Steinernema feltiae (Rhabditida: Steinernematidae) against Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), is considered as one of the most important pests of potato plants. Control of CPB is mainly based on chemical insecticides. However, control failure is often reported because of the rapid resistance development ability of CPB; therefore, there is an urgent need for integrated control methods. In this study, we evaluated the combined usage of insecticides chlorantraniliprole, spinosad, and spinetoram, which are registered for CPB control, with the entomopathogenic nematode Steinernema feltiae (Rhabditida: Steinernematidae).In addition, the efficacy of S. feltiae on a chlorantraniliprole-resistant CPB population exposed to synergistic chemicals PBO (Piperonyl butoxide), DEM (Diethyl maleate) and DEF (S,S,S-tributylphorotrithioate) inhibiting certain detoxification enzyme groups was determined. The tested insecticides showed no adverse effect on the survival and infectivity of S. feltiae and the isolate was considered compatible with integrated CPB control. This study also showed that pre-treatment with synergistic chemicals (particularly PBO and DEM) increased the efficacy of S. feltiae against CPB. To our knowledge, this is the first study determining the usage of entomopathogenic nematode + synergist combination. Therefore, further studies on the potential use of synergistic chemicals in combination with entomopathogenic nematodes should be performed under both laboratory and field conditions.

Design and Preliminary Testing of a Pneumatic Prototype Machine to Control the Colorado Potato Beetle

Highlights A pneumatic prototype machine to control the Colorado potato beetle (CPBs) was successfully designed, built, and tested in a potato field under real conditions. The pneumatic prototype machine is effective in dislodging CPB larvae from potato plants. ABSTRACT . The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is a real threat to potato crops when left uncontrolled. This insect pest is hard to control because it develops resistance to most chemical insecticides. To date, several alternatives including chemical, biological, and physical methods have been used to control CPB populations but have proven to be ineffective on their own. So far, the most reliable method at short and medium scales has been the use of chemicals, i.e., spraying insecticides onto potato plants at regular intervals throughout the life cycle of the CPB. However, the overuse of chemicals due to the resistance developed by the CPB can lead to serious health and environmental problems. The use of a pneumatic method to control the CPB seems to be a viable alternative compared to the use of chemicals. For this purpose, this research focused on engineering a pneumatic control device that could allow farmers to reduce their reliance on chemical insecticides. A pneumatic prototype machine using positive air pressure to dislodge CPBs from potato plant foliage was designed and built at the Department of Soils and Agri-Food Engineering of Université Laval. This prototype was tested in the field using three airflow velocities (31, 35, and 38 m/s) and two travel speeds (5 and 6 km/h). The results indicated that the airflow velocity and travel speed have no significant impact on dislodging the CPB (p = 0.0548 and 0.7033, respectively). However, the interaction between airflow velocities and the development stages of the CPB had a significant effect on dislodging the CPB (p = 0.0194). Overall, the most adequate airflow velocity that resulted in removing most of the CPB larvae from potato leaves was 35 m/s. Obtained results indicate that this pneumatic prototype machine could be efficiently used to control the CPB. However, extensive testing is required to confirm obtained results and investigate the effects of the pneumatic control on both the potato plant growth and the yield compared to other control means. Keywords: Airflow velocity, Colorado potato beetle, Pneumatic control, Potato, Travel speed.

Geographic Variation in Dominance of Spinosad Resistance in Colorado Potato Beetles (Coleoptera: Chrysomelidae).

Eastern New York State is frequently the site of Colorado potato beetle (Leptinotarsa decemlineata, Say) populations with the highest observed levels of insecticide resistance to a range of active ingredients. The dominance of a resistant phenotype will affect its rate of increase and the potential for management. On organic farms on Long Island, L. decemlineata evolved high levels of resistance to spinosad in a short period of time and that resistance has spread across the eastern part of the Island. Resistance has also emerged in other parts of the country as well. To clarify the level of dominance or recessiveness of spinosad resistance in different parts of the United States and how resistance differs in separate beetle populations, we sampled in 2010 beetle populations from Maine, Michigan, and Long Island. In addition, a highly resistant Long Island population was assessed in 2012. All populations were hybridized with a laboratory-susceptible strain to determine dominance. None of the populations sampled in 2010 were significantly different from additive resistance, but the Long Island population sampled in 2012 was not significantly different from fully recessive. Recessive inheritance of high-level resistance may help manage its increase.

Wildflower plantings in commercial agroecosystems promote generalist predators of Colorado potato beetle

Wildflower plantings in agroecosystems can support arthropod predators, and may have the potential to increase conservation biological control of pest species in nearby crops. Colorado potato beetle (CPB) is a significant defoliator of potato that is resistant to many forms of management. Promoting natural enemies of CPB by establishing perennial wildflower plantings in field margins may provide a measure of control for this pest. We examined the impacts of floral plantings on the abundance of known CPB predators, predation of CPB egg masses, and CPB populations in a commercial agroecosystem. Floral plantings increased the abundance of CPB predators, but did not significantly increase the rate of predation of sentinel CPB egg masses within field margins. Within nearby potato fields, predator abundance and predation rates on CPB eggs were unaffected by the presence of flowers. Colorado potato beetle abundance in potato fields was also not impacted by floral plantings. However, floral margins may provide improved overwintering opportunities for CPB, and further investigation is needed. Perennial wildflower plantings show potential for attracting predators that prey on CPB, but these benefits do not extend into nearby potato crops.

Modern Techniques in Colorado Potato Beetle (Leptinotarsa decemlineata Say) Control and Resistance Management: History Review and Future Perspectives.

Simple SummaryThe Colorado potato beetle (CPB) is one of the most important potato pest worldwide. It is native to U.S. but during the 20th century it has dispersed through Europe, Asia and western China. It continues to expand in an east and southeast direction. Damages are caused by larvae and adults. Their feeding on potato plant leaves can cause complete defoliation and lead to a large yield loss. After the long period of using only chemical control measures, the emergence of resistance increased and some new and different methods come to the fore. The main focus of this review is on new approaches to the old CPB control problem. We describe the use of Bacillus thuringiensis and RNA interference (RNAi) as possible solutions for the future in CPB management. RNAi has proven successful in controlling many pests and shows great potential for CPB control. Better understanding of the mechanisms that affect efficiency will enable the development of this technology and boost potential of RNAi to become part of integrated plant protection in the future. We described also the possibility of using single nucleotide polymorphisms (SNPs) as a way to go deeper into our understanding of resistance and how it influences genotypes.Colorado potato beetle, CPB (Leptinotarsa decemlineata Say), is one of the most important pests of the potato globally. Larvae and adults can cause complete defoliation of potato plant leaves and can lead to a large yield loss. The insect has been successfully suppressed by insecticides; however, over time, has developed resistance to insecticides from various chemical groups, and its once successful control has diminished. The number of available active chemical control substances is decreasing with the process of testing, and registering new products on the market are time-consuming and expensive, with the possibility of resistance ever present. All of these concerns have led to the search for new methods to control CPB and efficient tools to assist with the detection of resistant variants and monitoring of resistant populations. Current strategies that may aid in slowing resistance include gene silencing by RNA interference (RNAi). RNAi, besides providing an efficient tool for gene functional studies, represents a safe, efficient, and eco-friendly strategy for CPB control. Genetically modified (GM) crops that produce the toxins of Bacillus thuringiensis (Bt) have many advantages over agro-technical, mechanical, biological, and chemical measures. However, pest resistance that may occur and public acceptance of GM modified food crops are the main problems associated with Bt crops. Recent developments in the speed, cost, and accuracy of next generation sequencing are revolutionizing the discovery of single nucleotide polymorphisms (SNPs) and field of population genomics. There is a need for effective resistance monitoring programs that are capable of the early detection of resistance and successful implementation of integrated resistance management (IRM). The main focus of this review is on new technologies for CPB control (RNAi) and tools (SNPs) for detection of resistant CPB populations.

Regional differences in gene regulation may underlie patterns of sensitivity to novel insecticides in Leptinotarsa decemlineata.

Agricultural insect pests frequently exhibit geographic variation in levels of insecticide resistance, which are often presumed to be due to the intensity of insecticide use for pest management. However, regional differences in the evolution of resistance to novel insecticides suggests that other factors are influencing rates of adaptation. We examined median lethal concentration (LC50 ) bioassay data spanning 15 years and six insecticides (abamectin, imidacloprid, spinosad, cyantraniliprole, chlorantraniliprole, and metaflumizone) for evidence of regional differences in Leptinotarsa decemlineata baseline sensitivity to insecticides as they became commercially available. We consistently found that larvae from Colorado potato beetle populations from the northwestern USA had the highest baseline sensitivity to novel insecticides, while populations from the eastern USA had the lowest. Comparisons of gene expression between populations from these regions revealed constitutively elevated expression of an array of detoxification genes in the East, but no evidence of additional induction when exposed to imidacloprid. Our results suggest a mechanism for geographic variation in rates of adaptation to insecticides, whereby baseline levels of gene expression determine a population's response to novel insecticides. These findings have implications for the regional development of insecticide resistance management strategies and for the fundamental question of what determines the rate of adaptation to insecticides. © 2020 Society of Chemical Industry.

Profiling of RNAi sensitivity after foliar dsRNA exposure in different European populations of Colorado potato beetle reveals a robust response with minor variability

In recent years, substantial effort was spent on the exploration and implementation of RNAi technology using double-stranded RNA (dsRNA) for pest management purposes. However, only few studies investigated the geographical variation in RNAi sensitivity present in field-collected populations of the targeted insect pest. In this baseline study, 2nd instar larvae of 14 different European populations of Colorado potato beetle (CPB), Leptinotarsa decemlineata, collected from nine different countries were exposed to a foliarly applied diagnostic dose of dsactin (dsact) to test for possible variations in RNAi response. Only minor variability in RNAi sensitivity was observed between populations. However, the time necessary to trigger a dsRNA-mediated phenotypic response varied significantly among populations, indicated by significant differences in mortality figures obtained five days after treatment. An inbred German laboratory reference strain D01 and a Spanish field strain E02 showed almost 100% mortality after foliar exposure to 30 ng dsactin (equal to 0.96 g/ha), whereas another Spanish strain E01 was least responsive and showed only 30% mortality. Calculated LD50-values for foliarly applied dsact against strains D01 (most sensitive) and E01 (least sensitive) were 9.22 and 68.7 ng/leaf disc, respectively. The variability was not based on target gene sequence divergence or knock-down efficiency. Variability in expression of the core RNAi machinery genes dicer (dcr2a) and argonaute (ago2a) was observed but did not correlate with sensitivity. Interestingly, RT-qPCR data collected for all strains revealed a strong correlation between the expression level of dcr2a and ago2a (r 0.93) as well as ago2a and stauC (r 0.94), a recently described dsRNA binding protein in Coleopterans. Overall, this study demonstrates that sensitivity of CPB to sprayable RNAi slightly varies between strains but also shows that foliar RNAi as a control method works against all tested CPB populations collected across a broad geographic range in Europe. Thus, underpinning the potential of RNAi-based CPB control as a promising component in integrated pest management (IPM) and resistance management programs.