Potato Beetle Research Articles

The development of an egg-soaking method for delivering dsRNAs into spider mites

Recently, the first sprayable RNAi biopesticide, Ledprona, against the Colorado potato beetle, Leptinotarsa decemlineata, has been registered at the United States Environmental Protection Agency. Spider mites (Acari: Tetranychidae), a group of destructive agricultural and horticultural pests, are notorious for rapid development of insecticide/acaricide resistance. The management options, on the other hand, are extremely limited. RNAi-based biopesticides offer a promising control alternative to address this emerging issue. In this study, we i) developed an egg-soaking dsRNA delivery method; ii) evaluated the factors influencing RNAi efficiency, and finally iii) investigated the potential mode of entry of this newly developed egg-soaking RNAi method. In comparison to other dsRNA delivery methods, egg-soaking method was the most efficient, convenient/practical, and cost-effective method for delivering dsRNAs into spider mites. RNAi efficiency of this RNAi method was affected by target genes, dsRNA concentration, developmental stages, and mite species. In general, the hawthorn spider mite, Amphitetranychus viennensis, is more sensitive to RNAi than the two-spotted spider mite, Tetranychus urticae, and both of them have dose-dependent RNAi effect. For different life stages, egg and larvae are the most sensitive life stages to dsRNAs. For different target genes, there is no apparent association between the suppression level and the resultant phenotype. Finally, we demonstrated that this egg-soaking RNAi method acts as both stomach and contact toxicity. Our combined results demonstrate the effectiveness of a topically applied dsRNA delivery method, and the potential of a spray induced gene silencing (SIGS) method as a control alternative for spider mites.

Potential of Thuja occidentalis L. Essential Oil and Water Extracts against Field Crop Pests.

Thuja occidentalis L. essential oil (EOTO) and its compounds, such as terpinyl acetate, bornyl acetate, and β-thujone, are claimed to be highly effective against some storage pests, sanitary insects, or pests of fruit trees, while data about its use in protecting field crops are very scarce. There is also a lack of information in the literature about the insecticidal value of water extracts from T. occidentalis (WETOs). Both essential oils (EOs) and water extracts (WEs) from various plants have advantages and disadvantages in terms of their use as insecticides. EOs are generally more effective, but their preparation is more complicated and quite expensive. In turn, WEs are simple to prepare and cheap, but they often have limited effectiveness. Moreover, significant differences in responses exist depending on the species of the donor plant, the method of preparing the extract, its concentration, the species of the pest being controlled, the developmental stage, and even the gender of the pest. The goals of the research were to assess the effect of EOTO and WETOs prepared from dry and fresh matter on the mortality, feeding, and body mass changes of important crop pests, i.e., the black bean aphid, pea leaf weevil, and Colorado potato beetle (CPB), respectively, as well as on the mortality and voracity of non-target organism Asian lady beetle young larvae. EOTO showed significant aphicidal activity with LC50 = 0.8267% and 0.2453% after 42 h of the experiment for nymphs and wingless females of black bean aphid, respectively. Adults of CPB were more resistant to EOTO than aphids, with LC50 values for females equal to 1.5327% and 1.3113% after 48 h and after 72 h of the experiment. There was no significant effect of EOTO on CPB foraging. Calculated LC50 values for pea leaf weevil adults were lower than those for CPB (0.9638% and 0.8573% for males after 12 h and 24 h, respectively). In the case of this pest, a clear reduction in foraging was obtained, with higher concentrations of EOTO resulting in more pronounced reductions in foraging behavior. Concentrations of EOTO above 0.5%, which showed efficacy against the aphid, were lethal to 3-day-old larvae of the Asian lady beetle. WETOs, in turn, showed significant potential in inhibiting adult pea leaf weevil feeding, with very low or no effectiveness in reducing A. fabae and CPB, respectively.

Evaluation of cell-free supernatants from the symbiotic bacteria of entomopathogenic nematodes for controlling the colorado potato beetle [Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)]

AbstractThe Colorado potato beetle (CPB), Leptinotarsa decemlineata, poses a significant threat to potato crops globally and has developed resistance to numerous insecticides. Entomopathogenic nematodes (EPNs), from the genera Steinernema and Heterorhabditis, are promising biocontrol agents. This study aimed to identify the bacterial symbionts of ten native EPN isolates, evaluate the efficiency of cell free supernatants (CFSs) from their symbiotic bacteria against different developmental stages of CPB, and determine the effect of these CFSs on CPB developmental stages and lifespan. The recA gene region was utilized to determine the symbiotic bacteria of ten local EPNs. CFSs from these bacteria were applied orally and through contact to CPB’s various developmental stages (L1/L2, L3/L4 larval stages, and adults). Mortalities, developmental transition times, and lifespans of adults were observed. The CFSs showed significant toxicity to CPB, with higher efficiency against young larvae. The CFSs exhibited cumulatively lethal effects over time, particularly on L1/L2 larval stages. CFSs from X. bovienii exhibited the highest efficacy. In all cases, where larvae received CFSs orally or by contact, they failed to develop into pupae and adults. In contrast, the transition periods of old larvae to pupal and adult stages were comparable to those of the control group. Lifespans of adults differed based on bacterial isolates and application methods. This study shows the potential efficacy of CFSs from Xenorhabdus and Photorhabdus as biocontrol agents against CPB, particularly in its young larval stages. Further research is needed to unravel the mechanisms behind these effects and examine the impact on CPB mating and oviposition behaviors.

Encapsulation of Fennel and Basil Essential Oils in β-Cyclodextrin for Novel Biopesticide Formulation.

β-cyclodextrin (β-CD) is a good host for the encapsulation of fennel and basil essential oils (FEO and BEO, respectively) and the formation of inclusion complexes (ICs) using the co-precipitation method. According to the results of the GC/MS analysis conducted in this study, monoterpenes and monoterpenoids were the dominant chemical groups in total FEO, while in BEO, these two groups occurred along with sesquiterpenes and sesquiterpenoids. The presence of dominant compounds from both EOs was validated using the FT-IR spectra of ICs, which indicated successful complexation. Analyses conducted using SPME/GC-MS showed the continuous emission of volatiles over 24 h from both ICs. Under SEM, particles of both ICs appeared to have a rectangular or rhomboid morphology and few aggregates. The insecticidal properties of EOs and ICs with β-CD were tested on the Colorado potato beetle (CPB) as a model pest. The inclusion complex of β-CD with FEO altered the developmental dynamic and body mass of the CPB. The initial increase in the proteolytic activity of CPB larvae fed with potato plants sprayed with ICs was not maintained for long, and the proteolytic efficacy of treated larvae remained in line with that of the control larvae. Future investigations will focus on manipulating the volume of EOs used and the treatment duration for optimal efficacy and potential application.

The larval stage of the species Leptinotarsa decemlineata Say – contributions to the study of ontogenetic development, in the northern part of the country

The larval stage of the species <i>Leptinotarsa decemlineata</i> Say – contributions to the study of ontogenetic development, in the northern part of the country

Cyantraniliprole and Thiamethoxam Exposure Changes Expression of Transcripts Associated with Small Non-Coding RNA Processing in the Colorado Potato Beetle.

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) can cause extensive damage to agricultural crops worldwide and is a significant insect pest. This insect is notorious for its ability to evade various strategies deployed to control its spread and is known for its relative ease in developing resistance against different insecticides. Various molecular levers are leveraged by L. decemlineata for this resistance to occur, and a complete picture of the genes involved in this process is lacking. While small non-coding RNAs, including miRNAs, are differentially expressed in insects exposed to insecticides, levels of transcript coding for proteins underlying their synthesis remain to be characterized fully. The overarching objective of this work aims to fill that gap by assessing the expression of such targets in L. decemlineata exposed to cyantraniliprole and thiamethoxam. The expression status of Ago1, Ago2, Ago3, Dcr2a, Dcr2b, Expo-5, Siwi-1 and Siwi-2 transcripts were quantified via qRT-PCR in adult L. decemlineata treated with low and high doses of these compounds for different lengths of time. Variation in Ago1 and Dcr2b expression was notably observed in L. decemlineata exposed to cyantraniliprole, while thiamethoxam exposure was associated with the modulation of Dcr2a and Siwi-1 transcript levels. The down-regulation of Ago1 expression in L. decemlineata using dsRNA, followed by cyantraniliprole treatment, was associated with a reduction in the survival of insects with reduced Ago1 transcript expression. Overall, this work presents the insecticide-mediated modulation of transcripts associated with small non-coding RNA processing and showcases Ago1 as a target to further investigate its relevance in cyantraniliprole response.

The effect of Xenorhabdus bacteria metabolites on Colorado potato beetle (Leptinotarsa decemlineata) adult feeding and larval survival

Colorado Potato Beetle (CPB) is one of the most destructive potato pests that can quickly develop resistance to insecticides. Therefore, new safe and effective control strategies that are less susceptible to the development of resistance by CPB are urgently needed. Due to their complex mode of action, the likelihood of resistance development by target pests is generally low with antifeedants. In the present study, we assessed the effect of secondary metabolites of various Xenorhabdus bacteria species and strains on CPB adult feeding and on larval development. The metabolites were applied in the form of cell free supernatants (CFSs) from Xenorhabdus cultures. In bioassay 1, leaves treated with ten Xenorhabdus cultures were fed to CPB adults, and their feeding was assessed daily for one week. In bioassay 2, CPB egg masses were placed on the leaves treated with five bacterial cultures, and larval development to pupae was monitored. Out of the ten Xenorhabdus cultures tested, two strains exhibited a significant reduction in the feeding behavior of Colorado Potato Beetle adults, with reductions of up to 70% compared to the control. The effect of CFSs on larval development was variable, and when treated with X. khoisanae SGI 197, over 90% of larvae died in the first few days before reaching the 2nd instar, and complete mortality was achieved on the 8th day of the experiment. Our study is the first study to demonstrate the antifeedant effect of Xenorhabdus cultures towards herbivorous beetles, and the metabolites of these bacteria may have potential for CPB control. Clearly, the metabolites produced by X. khoisanae SGI-197 may be a promising tool for CPB larvae control with the potential to significantly decrease damage to potato plants.

Draft Genome Sequencing of the Bacillus thuringiensis var. Thuringiensis Highly Insecticidal Strain 800/15

The Bacillus thuringiensis serovar thuringiensis strain 800/15 has been actively used as an agent in biopreparations with high insecticidal activity against the larvae of the Colorado potato beetle Leptinotarsa decemlineata and gypsy moth Lymantria dispar. In the current study, we present the first draft genome of the 800/15 strain coupled with a comparative genomic analysis of its closest reference strains. The raw sequence data were obtained by Illumina technology on the HiSeq X platform and de novo assembled with the SPAdes v3.15.4 software. The genome reached 6,524,663 bp. in size and carried 6771 coding sequences, 3 of which represented loci encoding insecticidal toxins, namely, Spp1Aa1, Cry1Ab9, and Cry1Ba8 active against the orders Lepidoptera, Blattodea, Hemiptera, Diptera, and Coleoptera. We also revealed the biosynthetic gene clusters responsible for the synthesis of secondary metabolites, including fengycin, bacillibactin, and petrobactin with predicted antibacterial, fungicidal, and growth-promoting properties. Further comparative genomics suggested the strain is not enriched with genes linked with biological activities implying that agriculturally important properties rely more on the composition of loci rather than their abundance. The obtained genomic sequence of the strain with the experimental metadata could facilitate the computational prediction of bacterial isolates’ potency from genomic data.

Evidence of active oviposition avoidance to systemically applied imidacloprid in the Colorado potato beetle.

Agricultural pests can develop behavioral resistance to insecticides by choosing to feed or oviposit on insecticide-free hosts. As young larvae have relatively low mobility, oviposition preferences from female adults may play a critical role in shaping the evolutionary trajectory of pest populations. While oviposition avoidance of insecticide-treated hosts was found in different agriculture pests, it remains unclear whether female adults actively choose to occupy insecticide-free hosts. To address this question, we investigated feeding and oviposition preferences between imidacloprid-treated and imidacloprid-free plants in the Colorado potato beetle, Leptinotarsa decemlineata Say, a major potato pest. We performed behavioral choice assays on two strains that differed in both fecundity and insecticide resistance. We found that one strain preferred to feed on the insecticide-free plants and that this preference is not innate. Meanwhile, the other strain chose plants for feeding and oviposition randomly. Further analyses of the moving patterns of the beetles suggested that the oviposition preference in the first strain is likely due to active learning.

Diabrotica v. virgifera Seems Not Affected by Entomotoxic Protease Inhibitors from Higher Fungi.

Certain soil insects, such as the root-damaging larvae of the maize pest Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), are increasingly difficult to control because of recent bans of some insecticides. An alternative and safer approach may be the development of biopesticides based on entomotoxic defense proteins of higher fungi. Many of these potentially interesting proteins are protease inhibitors, and some have been shown to adversely affect insects. We examined the effects of the cysteine protease inhibitors macrocypin 1, 3, and 4 from Macrolepiota procera, clitocypin from Clitocybe nebularis, and cocaprin 1 and the serine protease inhibitor cospin 1 from Coprinopsis cinerea on D. v. virgifera. We confirmed the inhibition by mycocypins of the cysteine catalytic-type proteolytic activities in gut extracts of larvae and adults. The inhibition of pGlu-Phe-Leu-hydrolyzing activity was stronger than that of Z-Phe-Arg-hydrolyzing activity. Mycocypins and cospin resisted long-term proteolytic digestion, whereas cocaprin 1 was digested. Bioassays with overlaid artificial diet revealed no effects of proteins on neonatal mortality or stunting, and no effects on adult mortality. Immersion of eggs in protein solutions had little effect on egg hatching or mortality of hatching neonates. Microscopic analysis of the peritrophic matrix and apical surface of the midguts revealed the similarity between larvae of D. v. virgifera and the chrysomelid Leptinotarsa decemlineata, which are sensitive to these inhibitors. The resistance of D. v. virgifera to fungal protease inhibitors is likely due to effective adaptation of digestive enzyme expression to dietary protease inhibitors. We continue to study unique protein complexes of higher fungi for the development of new approaches to pest control.

Nearly complete genome sequences of the first two identified Colorado potato beetle viruses

The Colorado potato beetle is one of the most devastating potato pests in the world. However, its viral pathogens, which might have potential in pest control, have remained unexplored. With high-throughput sequencing of Colorado potato beetle samples derived from prepupal larvae which died from an unknown infection, we have identified two previously unknown RNA viruses and assembled their nearly complete genome sequences. The subsequent genetic and phylogenetic analysis demonstrated that the viruses, tentatively named Leptinotarsa iflavirus 1 and Leptinotarsa solinvi-like virus 1, are the novel representatives of the Iflaviridae and Solinviviridae families, respectively. To the best of our knowledge, these are the first sequencing-confirmed insect viruses derived from Colorado potato beetle samples. We propose that Leptinotarsa iflavirus 1 may be associated with a lethal disease in the Colorado potato beetle.

Efficacy of three bioinsecticides for control of Colorado potato beetle on potatoes

An experiment was conducted to evaluate the effectiveness of three commercial bioinsecticides based on the spores of Bacillus thuringiensis var. thuringiensis. The control areas were areas where no protective measures were applied. The data showed that all bioinsecticides tested were highly effective against first, second and third instar larvae of the Colorado potato beetle Leptinotarsa decemlineata. The drug “Bitoxibacillin” ensured 100% death of larvae on day 8 at a drug concentration of 10 g/l. Combined preparation “Bitoxibacillin + GUMI” containing spores of Bacillus thuringiensis var. thuringiensis and sodium salts of humic acids, led to 100% death of larvae on the 7th day of observation. As the dosage of the drug was reduced to 5 mg/L, its effectiveness decreased to a 92% mortality rate within 9 days. The complex drug “Bitoxibacillin + Actarofid” contributed to 100% death of Colorado potato beetle larvae of all ages on the 7th day of observation at a concentration of 10 g/l. During the same time interval, 82% and 94% of the larvae died at drug concentrations of 2 mg/l and 5 mg/l, respectively.

Evaluation of at-plant systemic options for Colorado potato beetle management in Wisconsin, 2023

Evaluation of at-plant systemic options for Colorado potato beetle management in Wisconsin, 2023

Phytosanitary state of open-field vegetable crop agroecosystems of the genus Solanum, Raphanus, Brassica in the central part of the Right-Bank Forest-Steppe of Ukraine

Goal. Phytosanitary assessment and determination of pest and disease prevalence and development in open-field vegetable crop plantings of the genus Solanum (tomato, pepper, eggplant), genus Raphanus (radish, oilseed radish, common radish, black radish, daikon), and genus Brassica (cabbage, cauliflower, broccoli) in the Central Part of the Right-Bank Forest-Steppe Region of Ukraine.&#x0D; Methods. The research was conducted using established entomological, phytopathological, and horticultural methods. From 2008 to 2022, the population, distribution, and development of pests and phytopathogens were assessed in households and small farms within the Cherkasy region of Ukraine.&#x0D; Results. Among the dominant pest species in the agroecosystems of vegetable crops from the genus Solanum, insects accounted for 80% (8 species), followed by mites at 10% (1 species), and slugs at 10% (1 species). In agroecosystems of Brassicaceae crops, insects caused significant damage, constituting 94% (16 species) of the total pest structure, along with naked snails (1 species). The area of infestation in tomato, sweet pepper, and eggplant crops by phytophagous insects ranged from 13% to 98%, with plant damage ranging from 14% to 65%. Common spider mites accounted for 26%. Exceedances of the Economic Pest Threshold (EPT) were observed, such as Leptinotarsa decemlineata Say at 2.6 times, Gryllotalpa gryllotalpa L., Trialeurodes vaporariorum Wstw., Agrotis segetum Denis &amp; Schiff., and Lacanobia oleracea at 2.2 times, Agriotes spp. larvae at 1.4 times, and Tetranychus urticae Koch. at 1.9 times the threshold levels. The highest area of infestation in Brassicaceae crops was found for Eurydema ventralis (46.7%), Pieris brassicae (42.4%), Agrotis segetum Denis &amp; Schiff. (41.6%), Phyllotreta crusiferae and Phyllotreta undulate (37.6—37.8%), and Brevicoryne brassicae (26.6%). Exceedances of the EPT were recorded at 1.1—2.5 times for these pests. In the structure of the phytopathogenic complex of vegetable crop agroecosystems, fungi were dominant, accounting for an average of 49—58%. Viral pathogens had the smallest share, approximately 6—8%, causing mosaic diseases. Bacterial and oomycete agents occupied an intermediate position in the pathogenic complex structure. Nevertheless, their negative impact on plant health could be significant.&#x0D; Conclusions. In the Cherkasy region, which encompasses the central part of the Right-Bank Forest-Steppe of Ukraine, approximately 75% of surveyed vegetable crop plantings, including tomatoes, peppers, eggplants, radishes, oilseed radishes, common radishes, black radishes, daikons, cabbages, cauliflowers, and broccolis, exhibit high pest infestations exceeding the EPT thresholds, indicating an ecologically hazardous phytosanitary state. In these agroecosystems, insects dominated, representing 80% and 94% of the pest structure in Solanum and Brassicaceae crops, respectively. Additionally, significant damage was attributed to naked snails (Kailie gliemeži) and, in the case of Solanum crops, mites (Tetranychus urticae Koch.). EPT exceedances ranged from 1.1 to 2.5 times, depending on the pest species. Fungi, causing mycoses, dominated the phytopathogenic complex structure, ranging from 14% to 40% (max 88—90%). The prevalence of diseases varied from 21% to 38%, with disease development rates ranging from 21% to 33%. Among the identified phytopathogens, five species are among the world’s most dangerous: Pseudomonas syringae and Xanthomonas campestris (bacteria), Botrytis cinerea and Fusarium oxysporum (fungi), and Phytophthora infestans (oomycete), which require strict control of their populations.

Control of Colorado potato beetle on potato by isocycloseram, 2023

Control of Colorado potato beetle on potato by isocycloseram, 2023

Colorado potato beetle control in potato with tolfenpyrad in combination with adjuvants, 2023

Colorado potato beetle control in potato with tolfenpyrad in combination with adjuvants, 2023

Baseline Susceptibility to a Novel dsRNA-Based Insecticide across US Populations of Colorado Potato Beetle

The Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is an insect defoliator of the potato, Solanum tuberosum L. This species thrives in agricultural environments because of its flexible and complex life history, as well as its ability to evolve insecticide resistance. As a result, it has become a widely distributed agricultural pest. Ledprona (trade name Calantha) is a recently developed novel double-stranded RNA (dsRNA) insecticide that controls populations of Colorado potato beetle through RNA interference (RNAi). Previous studies have demonstrated the efficacy of ledprona through laboratory, greenhouse, and field studies. Colorado potato beetles from geographically distinct populations are known to vary in their response to insecticides, including experimental compounds based on RNAi. We tested the mortality and foliage consumption of beetles from different areas in the US treated with ledprona and found significant variation in both parameters. The beetles originating from New York were significantly less susceptible to ledprona in leaf disc assays compared to other populations. However, currently there is no evidence of reduced performance of ledprona against that population under field conditions, possibly because intoxicated beetles cannot withstand multiple stressors present in the field. The results of this study confirmed that the ledprona efficacy differs among geographically distinct populations, which may have implications for managing Colorado potato beetles.

Predator densities alter the influence of non‐consumptive effects on the population dynamics of an agricultural pest

Abstract Augmentative release of predators is used in agriculture to suppress pest populations and minimise crop damage. However, predators affect prey populations not only through consumption but by inducing changes to prey morphology, physiology, behaviour and life history. These risk‐induced trait responses can increase prey fitness, potentially reducing the efficacy of certain predators as biocontrol agents. We investigated how non‐consumptive effects contribute to the overall influence of predators by modelling the effect of the predator Podisus maculiventris on the population dynamics of a major agricultural pest, the Colorado potato beetle (Leptinotarsa decemlineata). We developed a demographic model incorporating both consumption and non‐consumptive Podisus‐induced shifts in beetle reproductive strategy. Our model combines data from multiple mechanistic experiments showing that predator‐exposed beetles produce fewer offspring but increase offspring provisioning, and that provisioned larvae have increased survival when predators are present. We simulated beetle densities across multiple beetle generations and a range of predator densities. The influence of non‐consumptive effects depended on predator density. At low predator densities, non‐consumptive effects strengthened the negative effect of predators by up to 45%, and risk‐induced changes to offspring provisioning had a stronger effect on prey densities than reduced offspring quantity. In contrast, at high predator densities, non‐consumptive effects changed the effect of predators by &lt;5%, likely because beetle densities were very low both with and without non‐consumptive effects. Our results suggest that even adaptive responses to predation risk by prey do not necessarily reduce the ability of predators to suppress pest populations.

Investigation of genetic diversity and polyandry of Leptinotarsa decemlineata using X-linked microsatellite markers

A panel of X-linked microsatellite markers was newly designed using the data from a previous sequencing project available in NCBI and used for a study of the Colorado potato beetle (CPB, Leptinotarsa decemlineata) X-haplotype variability. The analysis of scaffolds 49 and 61 (newly identified as fragments of CPB chromosome X) found ten high-quality markers, which were arranged in two PCR multiplexes and evaluated in both 420 CPB adults, collected from 14 localities of Czechia and Slovakia, and 866 larvae from five single-female families from two more Czech localities. Length polymorphisms found in 6 loci have predicted 192 potential X-haplotypes, however, only 36 combinations were detected in the adult males (N = 189), and seven additional ones in the larvae. The X-haplotypes were also generally unevenly distributed; five of the most frequent haplotypes were detected in 55% of males, 19 repeating up to ten-times in 38.7% of males and the remained 12 occurred uniquely in 6.3% of males. Bulk analysis of X-haplotypes dissimilarity indicated seven haplotype groups diversified by mutations and recombinations. Two haplotypes showed a distinctive regional distribution, which indicates an east–west disruption of CPB migration probably caused by different environments of localities in the South Bohemia region and Vysocina region. On the contrary, the results indicate a south–north migration corridor alongside the Vltava River. In the single-female families, from 6 to 13 distinct paternal haplotypes were detected, which proved and quantified a frequented polyandry in CPB.

Evolution of chemosensory genes in Colorado potato beetle, Leptinotarsa decemlineata.

Associating with plant hosts is thought to have elevated the diversification of insect herbivores, which comprise the majority of global species diversity. In particular, there is considerable interest in understanding the genetic changes that allow host-plant shifts to occur in pest insects and in determining what aspects of functional genomic diversity impact host-plant breadth. Insect chemoreceptors play a central role in mediating insect-plant interactions, as they directly influence plant detection and sensory stimuli during feeding. Although chemosensory genes evolve rapidly, it is unclear how they evolve in response to host shifts and host specialization. We investigate whether selection at chemosensory genes is linked to host-plant expansion from the buffalo burr, Solanum rostratum, to potato, Solanum tuberosum, in the super-pest Colorado potato beetle (CPB), Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). First, to refine our knowledge of CPB chemosensory genes, we developed novel gene expression data for the antennae and maxillary-labial palps. We then examine patterns of selection at these loci within CPB, as well as compare whether rates of selection vary with respect to 9 closely related, non-pest Leptinotarsa species that vary in diet breadth. We find that rates of positive selection on olfactory receptors are higher in host-plant generalists, and this signal is particularly strong in CPB. These results provide strong candidates for further research on the genetic basis of variation in insect chemosensory performance and novel targets for pest control of a notorious super-pest.