Lygus Species Research Articles

Lygus Hahn in Turkey with a new subspecies of Lygus wagneri Remane (Hemiptera: Heteroptera: Miridae)

The paper presents all species of Lygus Hahn in Turkey. In this study, a total of 228 Lygus samples collected from Çankırı between 2013–2014 are evaluated. As a result, a total of six species of Lygus are determined from Turkey. In addition, Lygus wagneri ozdikmeni ssp. n., a new subspecies of Lygus wagneri from Çankırı province of Turkey is described. Habitus of holotype (male) and its genitalia are photographed. The newly described subspecies differs significantly from the nominative subspecies of Lygus wagneri and the other closely related Lygus species in terms of genital morphology and external morphology. The distribution data in Turkey and the world of all Lygus species are also given in the text. Accordingly, an identification key for all Lygus species in Turkey is provided.

Diyarbakır ili pamuk alanlarındaki Lygus (Hemiptera: Miridae) türleri, yayılış alanları ve popülasyon gelişimi

Many insect pests infest cotton (Gossypium hirsutum L.) crop, resulting in significant economic losses. The tarnished plant bugs (Lygus species) greatly damage the cotton crop during all growth stages. This study determined Lygus species infesting cotton in Diyarbakır province, their distribution, and population dynamics during 2020 and 2021. Lygus species samples were collected from 244 fields in 7 districts of the province by using either D-vac or sweep net based on the phenological period of cotton. Population dynamics of the species were monitored weekly by using sweep net and D-vac from two fields situated in the Sur (Gencan village) and Çınar (Şükürlü village) districts of the province during both years. Two species including Lygus gemellatus (Herrich-Schäffer) and L. pratensis (Linnaeus) were identified during the study. Lygus gemellatus was the most common and abundant species observed in 91.2% and 74.7% of the surveyed fields during 2020 and 2021, respectively. The species were recorded at the end of May (before flowering) during both years, and their populations increased afterward. The peak population of both species was observed during the boll maturation period. The D-vac trapped a statistically higher number of Lygus bugs than the sweep net at Gencan (p

Identification and delimitation of the trans-Palearctic Lygus species (Insecta: Heteroptera: Miridae) using integrative approach

Abstract Lygus (Insecta: Heteroptera: Miridae) is a Holarctic genus, and some of its representatives are important pests. Determining the Lygus species identity and their interrelationships is challenging. Our study aimed to delimit five trans-Palearctic species of this group: L. gemellatus, L. pratensis, L. punctatus, L. rugulipennis and L. wagneri. We implemented analyses of morphological characters, morphometrics, cytochrome c oxidase subunit I (COI) and 16S rRNA sequences. The results showed that those species could be delimited using morphology and most species pairs were different in morphometrics. Both COI and 16S rRNA were useful for species identification. Resulting phylogenetic trees contained two highly supported clades. One clade included species known from the Palearctic only, the other clade contained species with Nearctic and Holarctic distribution. Species were mostly poorly supported or non-monophyletic. Molecular species delineation approaches yielded results that generally did not correspond to the morphologically delimited species.

Biology, Ecology, and Pest Management of the Tarnished Plant Bug, Lygus lineolaris (Palisot de Beauvois) in Southern Row Crops.

Simple SummaryThe tarnished plant bug, Lygus lineolaris, is a polyphagous, sap-feeder that causes significant economic damage in several field crops, especially cotton (Gossypium hirsutum L.) in the mid-southern United States. In 2020, it was reported that 4.8 million acres of cotton were infested by Lygus spp. in the United States. A broad host range, polyphagous feeding behavior and high mobility of this pest along with resistance development to conventional pesticides helped them establish as a significant pest of concern for cotton growers in the mid-south. Since the publication of a review by Layton (2000) on damage caused by Lygus lineolaris, many new research studies have been published on the Lygus biology, ecology, and integrated pest management strategies. A comprehensive review paper that summarizes these latest research developments and Lygus management strategies will be useful for researchers and cotton growers. In this review, we report and discuss the latest developments in Lygus research and the new control strategies that have been developed in the last two decades.The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), (Hemiptera: Miridae) is considered the most damaging pest of cotton (Gossypium hirsutum L.) in the mid-southern United States, although it is established throughout the United States, southern Canada, and northern Mexico. The introduction of transgenic crops for the control of moths in the Heliothine complex and eradication of the boll weevil, Anthonomus grandis, from much of the United States led to greatly reduced pesticide use in cotton fields, which allowed L. lineolaris to emerge as a new primary pest of cotton in the mid-southern United States. Since the publication of a review by Layton (2000) on damage caused by Lygus lineolaris, many new studies have been published on the changes in host range, population dynamics, sampling methods and thresholds, cultural practices, sex pheromones and attractant blends, novel pesticides and insecticide resistance mechanisms, olfactory and feeding behaviors, introduction of biological control agents, host-plant resistance mechanisms, and new molecular and genetic tools for integrated pest management of Lygus species in cotton and other important crops. Here, we review and discuss the latest developments in L. lineolaris research in the last two decades.

Identification of simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) that are associated with the nectariless trait of Gossypium hirsutum L

Cotton (Gossypium hirsutum L.) has nectar containing modified stomates called nectaries that can be located on leaves, bracts or calyces. The nectar attracts some beneficial insects such as bees, but also predatory damaging insects such as heliothines and Lygus species. There is a naturally occurring mutation that eliminates the nectar containing nectaries and makes the cotton plants less attractive to insects. The nectariless (ne) trait is associated with a double recessive mutation of two genes (ne1 and ne2) on homeologous chromosomes 12 and 26. Expression of the trait can be variable and is also affected by environmental conditions. This makes accurately selecting for the trait based on phenotype difficult. This study identified SSR and SNP markers that can be used by breeders for marker assisted selection (MAS) of the nectariless trait. DNA markers associated with the genes conditioning the trait and used for MAS, will allow cotton cultivars to be easily developed that have decreased attractiveness to insects and reduce the need for insecticides, especially those harmful to beneficial insects such as honeybees.

Examining potential intra-guild predation of Peristenus relictus by Geocoris punctipes, and its effects on the biological control of Lygus lineolaris

The generalist predator Geocoris punctipes (Say) and the parasitoid Peristenus relictus (Ruthe) are Lygus bug natural enemies. Augmentative biological control of some Lygus species has been attempted using either the predatory bug, or the parasitoid, but never in combination. In the present study, in laboratory assays, we determined whether G. punctipes engaged in intra-guild predation of P. relictus while developing in nymphs of Lygus lineolaris Palisot de Beauvois. In choice and no-choice experiments, G. punctipes preyed on more first and second instar nymphs of L. lineolaris than third and fourth instar nymphs. In choice and no-choice experiments G. punctipes ate more L. lineolaris nymphs that contained P. relictus eggs than nymphs containing P. relictus larvae; no nymphs containing P. relictus pupae were eaten. In experimental arenas in the laboratory, simultaneous release of G. punctipes and P. relictus achieved an additive effect on the mortality of L. lineolaris, killing 90, 80 and 70 percent of first, second and third instar nymphs, respectively. Although those are encouraging results for pest management, additional research on the interactions between these two natural enemies in commercial strawberry fields is needed before practical recommendations can be made.

Documenting the expanded southern range of the introduced parasitoid Peristenus relictus (Hymenoptera: Braconidae) in California

ABSTRACTThe parasitoid Peristenus relictus was established in California to help regulate Lygus species. This study surveyed the San Joaquin Valley and South Coast of California to determine this parasitoid’s current southern geographic range. Peristenus relictus recoveries were made in all sampled counties, including Santa Barbara and Ventura along the coast, and Tulare, Kings and Kern inland. Parasitism was notably high in Santa Barbara County, where 61.7% of Lygus nymphs collected from weedy plants were parasitised. However, as parasitism was scarce in the San Joaquin Valley (0–12.5%), future research should examine possible inhibitors (e.g. climate) of this biological control.

Efficiency of volatile baited sticky traps for the Tarnished Plant Bug (Lygus lineolaris) in strawberry fields

AbstractInsecticides have adverse effects on human health and the environment. Thus, the development of non‐chemical replacement to manage insect pests is urgent. An alternative is to bait sticky traps with attractive insect sex pheromones or plant volatiles. In Quebec, the tarnished plant bug (Lygus lineolaris) is a major insect pest. We tested the efficiency of sex pheromones (mixture of hexyl butyrate (HB), (E)‐2‐hexenyl butyrate (E2HB) and (E)‐4‐oxo‐2‐hexenal (KA)) and sunflower (Helianthus annuus) volatiles (pinene, sabinene and phenylacetaldehyde) as sticky trap baits for the tarnished plant bug in strawberry fields of the Laurentians in Southern Québec, Canada. The pheromones decreased the number of tarnished plant bug caught in the traps compared to a control. The sunflower volatile did not have any effect on the number of individuals caught in the traps. Different Lygus species use HB, E2HB and KA in different ratios for sexual signals and alarm signals and for species recognition. GC‐MS analysis of the sex pheromone bait revealed that the ratios between the three main compounds did not match the intended ratio for the L. lineolaris species. This mismatch probably explains our results. Individuals were not attracted to sunflower volatiles. Our results point to the difficulty of manufacturing and using sex pheromones as baits. Future work should assess the effect of several pheromone ratios.

Quantifying Lygus (Hemiptera: Miridae) damage in faba bean (Fabaceae) seeds using shortwave-infrared imaging

AbstractLygus Hahn (Hemiptera: Miridae) feeding in faba beans (Vicia faba Linnaeus (Fabaceae)) often results in a reduction in seed quality and economic losses. Traditionally, seed damage is assessed subjectively through visual examination by a trained individual, but the use of non-destructive imaging to evaluate seed quality is gaining momentum. The focus of this study was to determine the ability to quantify Lygus species damage in faba bean using shortwave-infrared imaging and two analysis techniques: (1) spectral angle mapper and (2) simple reflectance indices. Seed samples were visually assessed for damage before imaging in 242 wavebands between 980 and 2500 nm. Four spectral intervals, involving 102 wavebands, were identified as optimal for the detection of seed damage using spectral angle mapper. A strong relationship was obtained between the area of seed damage derived using spectral angle mapper and visually (R2 = 0.95). Seed damage derived by thresholding of two normalised faba bean damage indices involving reflectance at 1086 and 1313 nm and 2218 and 2342 nm also showed a strong relationship with the visual assessment (R2 = 0.92). The two image analysis techniques provided similar results. The study suggests that imaging in the shortwave-infrared wavelengths and the derivation of simple indices can effectively quantify faba bean damage by Lygus feeding.

RNA interference-mediated knockdown of eye coloration genes in the western tarnished plant bug (Lygus hesperus Knight).

Insect eye coloration arises from the accumulation of various pigments. A number of genes that function in the biosynthesis (vermilion, cinnabar, and cardinal) and importation (karmoisin, white, scarlet, and brown) of these pigments, and their precursors, have been identified in diverse species and used as markers for transgenesis and gene editing. To examine their suitability as visible markers in Lygus hesperus Knight (western tarnished plant bug), transcriptomic data were screened for sequences exhibiting homology with the Drosophila melanogaster proteins. Complete open reading frames encoding putative homologs for all seven genes were identified. Bioinformatic-based sequence and phylogenetic analyses supported initial annotations as eye coloration genes. Consistent with their proposed role, each of the genes was expressed in adult heads as well as throughout nymphal and adult development. Adult eyes of those injected with double-stranded RNAs (dsRNAs) for karmoisin, vermilion, cinnabar, cardinal, and scarlet were characterized by a red band along the medial margin extending from the rostral terminus to the antenna. In contrast, eyes of insects injected with dsRNAs for both white and brown were a uniform light brown. White knockdown also produced cuticular and behavioral defects. Based on its expression profile and robust visible phenotype, cardinal would likely prove to be the most suitable marker for developing gene editing methods in Lygus species.

Molecular and Morphological Identifications Reveal Species Composition of Lygus (Hemiptera: Miridae) Bugs in Potatoes Fields in the Lower Columbia Basin of the United States.

Lygus bugs are highly polyphagous insect pests. In recent years, Lygus bugs have become more conspicuous on potato, Solanum tuberosum L., fields in the Pacific Northwest, particularly in the Lower Columbia Basin. There are concerns that direct feeding damage or potential pathogen transmission can reduce yield. Lygus species on potatoes in the region are collectively identified as 'Lygus bugs'. Overlapping physical traits and the fact that the same species exhibit morphological variations across a geographic range makes it difficult to identify Lygus to species level. Thus, in this study we used DNA barcodes in combination with morphological characters to identify Lygus species on potatoes. Three species were identified in the Lower Columbia Basin: Lygus hesperus (Knight) and Lygus elisus L. were the most common, whereas Lygus keltoni L. was the least common. Interspecific genetic distances among Lygus species were relatively low, ranging from 0.013 to 0.004. Neighbor-joining (NJ) tree clustered L. hesperus and L. elisus into two major clades, with L. keltoni forming a subclade within L. hesperus clade. Statistical parsimony analysis corroborated findings from phylogenetic analysis with L. keltoni and L. hesperus sharing one haplotype. Our study demonstrates the utility of integrating morphology and molecular markers in identifying morphologically similar species such as Lygus bugs. The study also serves as a fundamental step in contributing to developing suitable management strategies against Lygus bugs on potato.

Seasonality and species composition of Peristenus (Hymenoptera: Braconidae) species, and Lygus (Hemiptera: Miridae) species parasitism in southern Alberta, Canada

ABSTRACTWe report a long-term survey summarising the seasonal variation in species composition of Peristenus species, and their levels of parasitism in an assemblage of Lygus spp., over more than 10 years in southern Alberta in western Canada. Plants sampled include alfalfa (Medicago sativa L.), canola (Brassica napus L.), and stands of different weed and grass species commonly found on crop field edges. Three native Peristenus species (Peristenus dayi, Peristenus mellipes, and Peristenus howardi) were recorded in 2003–2011 and 2013–2015. In laboratory trials, P. mellipes emerged 13 days earlier than P. howardi. Degree-days for field-collected individuals suggested a sequential occurrence during the growing season: P. dayi appears early in the season, followed by P. mellipes, and later on by P. howardi. Studies of species composition and phenology of native parasitoids of insect pests provide valuable baseline information when considering introduction of exotic agents, and contribute to the management and improvement of conservation biological control by endemic natural enemies in agricultural systems.

A transgenic approach for controlling Lygus in cotton.

Lygus species of plant-feeding insects have emerged as economically important pests of cotton in the United States. These species are not controlled by commercial Bacillus thuringiensis (Bt) cotton varieties resulting in economic losses and increased application of insecticide. Previously, a Bt crystal protein (Cry51Aa2) was reported with insecticidal activity against Lygus spp. However, transgenic cotton plants expressing this protein did not exhibit effective protection from Lygus feeding damage. Here we employ various optimization strategies, informed in part by protein crystallography and modelling, to identify limited amino-acid substitutions in Cry51Aa2 that increase insecticidal activity towards Lygus spp. by >200-fold. Transgenic cotton expressing the variant protein, Cry51Aa2.834_16, reduce populations of Lygus spp. up to 30-fold in whole-plant caged field trials. One transgenic event, designated MON88702, has been selected for further development of cotton varieties that could potentially reduce or eliminate insecticide application for control of Lygus and the associated environmental impacts.

Transcriptome-Based Identification of ABC Transporters in the Western Tarnished Plant Bug Lygus hesperus

ATP-binding cassette (ABC) transporters are a large superfamily of proteins that mediate diverse physiological functions by coupling ATP hydrolysis with substrate transport across lipid membranes. In insects, these proteins play roles in metabolism, development, eye pigmentation, and xenobiotic clearance. While ABC transporters have been extensively studied in vertebrates, less is known concerning this superfamily in insects, particularly hemipteran pests. We used RNA-Seq transcriptome sequencing to identify 65 putative ABC transporter sequences (including 36 full-length sequences) from the eight ABC subfamilies in the western tarnished plant bug (Lygus hesperus), a polyphagous agricultural pest. Phylogenetic analyses revealed clear orthologous relationships with ABC transporters linked to insecticide/xenobiotic clearance and indicated lineage specific expansion of the L. hesperus ABCG and ABCH subfamilies. The transcriptional profile of 13 LhABCs representative of the ABCA, ABCB, ABCC, ABCG, and ABCH subfamilies was examined across L. hesperus development and within sex-specific adult tissues. All of the transcripts were amplified from both reproductively immature and mature adults and all but LhABCA8 were expressed to some degree in eggs. Expression of LhABCA8 was spatially localized to the testis and temporally timed with male reproductive development, suggesting a potential role in sexual maturation and/or spermatozoa protection. Elevated expression of LhABCC5 in Malpighian tubules suggests a possible role in xenobiotic clearance. Our results provide the first transcriptome-wide analysis of ABC transporters in an agriculturally important hemipteran pest and, because ABC transporters are known to be important mediators of insecticidal resistance, will provide the basis for future biochemical and toxicological studies on the role of this protein family in insecticide resistance in Lygus species.

Geographically Based Diversity in Mitochondrial DNA of North American Lygus lineolaris (Hemiptera: Miridae)

Abstract The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is a highly polyphagous insect pest. It is the most widely distributed Lygus species in North America, and it is the most prevalent member of the genus Lygus in the eastern half of the continent. We sampled multiple populations of L. lineolaris from three disparate regions of North America, and used parts of the mitochondrial genes cytochrome oxidase 1 and cytochrome oxidase 2 as markers to assess intraspecific diversity of this species. Results indicated that there is an association between genetic population structure and geography. Neighbor-joining, maximum parsimony, Bayesian inference analysis, and maximum likelihood trees suggested that most L. lineolaris individuals belong to two closely related clades showing sympatric distribution. Mitochondrial DNA haplotypes common to widely dispersed populations were observed. Morphological identities of five L. lineolaris samples that formed an outlier clade indicated incongruence between morphological identity and genetic data. Individuals from the two major clades and one disparate clade did not exhibit recognizable morphological differences. No strong host plant associations were observed among clades, thus, genetic structuring in this species appears to mostly be geographically based. This study represents the first attempt to survey cytochrome oxidase 1 and cytochrome oxidase 2 variation within L. lineolaris and to use those genes to construct a molecular phylogeny for this species.

Regional Assemblages of Lygus (Heteroptera: Miridae) in Montana Canola Fields

Abstract Sweep net sampling of canola (Brassica napus L.) was conducted in 2002 and 2003 to determine Lygus (Heteroptera: Miridae) species composition and parasitism levels in four regions of Montana. Regardless of region or seasonal change, Lygus elisus (Van Duzee) was the dominant species in all canola fields sampled, averaging 60–99% of the total adult populations. Lygus borealis (Kelton), Lygus keltoni (Schwartz) and Lygus lineolaris (Palisot) were detected at much lower levels. Total lygus population density was greatest in the southwest and central regions. The northeast and southwest regions had the greatest lygus species diversity. The proportion of L. elisus increased from early to late crop maturity stages in the southwest and central regions while there was no change in northeast and southwest canola production regions. Nymphal stages III–V were dissected to detect parasitism in 2003 only. Parasitism was found to be negligible in the dissection of 1,230 nymphs. Lygus population densities in can...

Second International Lygus Symposium Asilomar Conference Grounds, Pacific Grove, California, April 15-19 2007

The Second International Lygus Symposium brought together 52 entomologists from six nations and 11 states representing universities, public agencies, and private entities to discuss the latest research on Lygus species and their relatives. Symposium topics included Lygus biology, behavior and ecology, IPM, insecticides and resistance, and biological control. Papers and posters dealt with Lygus as a pest of several crops, including cotton, strawberries, seed alfalfa, canola, dry beans, cucumbers, cereals, peaches, and new crops guayule and lesquerella. Intercrop movement of Lygus2008200820082008 species was another important topic of many presentations. In the capstone session, participants identified needs and priorities for ongoing Lygus research and education (available at http://ag.arizona.edu/apmc/Arid_SWPMC_RAMP.html). The conference was sponsored in part by FMC Corporation, the University of Arizona Arizona Pest Management Center, the University of California Statewide IPM Program, and a grant to El...

Second International Lygus Symposium

The Second International Lygus Symposium brought together 52 entomologists from six nations and 11 states representing universities, public agencies, and private entities to discuss the latest research on Lygus species and their relatives. Symposium topics included Lygus biology, behavior and ecology, IPM, insecticides and resistance, and biological control. Papers and posters dealt with Lygus as a pest of several crops, including cotton, strawberries, seed alfalfa, canola, dry beans, cucumbers, cereals, peaches, and new crops guayule and lesquerella. Intercrop movement of Lygus2008200820082008 species was another important topic of many presentations. In the capstone session, participants identified needs and priorities for ongoing Lygus research and education (available at http://ag.arizona.edu/apmc/Arid_SWPMC_RAMP.html). The conference was sponsored in part by FMC Corporation, the University of Arizona Arizona Pest Management Center, the University of California Statewide IPM Program, and a grant to Ellsworth et al. (CRIS# 0207436) from the USDA-CSREES, Risk Avoidance and Mitigation Program (RAMP).

EAG-Active Herbivore-Induced Plant Volatiles Modify Behavioral Responses and Host Attack by An Egg Parasitoid

Volatiles emitted by plants in response to feeding by Lygus species were tested in neurophysiological, behavioral, and parasitism trials with Anaphes iole, an egg parasitoid of Lygus. Electroantennogram analyses indicated that A. iole antennae responded to most herbivore-induced plant volatiles (HIPVs) tested and that females were usually more responsive than males. Antennal responses to (Z)-3-hexenyl acetate and methyl salicylate were among the strongest. Behavioral assays in a four-arm olfactometer demonstrated that response of female wasps to (Z)-3-hexenyl acetate varied greatly depending on preconditioning regime. Preconditioning wasps to complex host-plant odors led to stronger preference than did a single preconditioning stimulus, i.e., (Z)-3-hexenyl acetate. In a horizontal wind tunnel, female wasps were attracted by methyl salicylate and alpha-farnesene. Parasitism of Lygus lineolaris eggs by A. iole in a cotton field was greater when the eggs were associated with (Z)-3-hexenyl acetate or alpha-farnesene than with controls. Overall, the results of this study show that A. iole can perceive a variety of plant volatiles released after its host damages plants, that the degree of associative learning in A. iole can be manipulated based on preconditioning regime, and that single synthetic HIPVs are attractive to A. iole and can be used to increase attack rates on host eggs. Therefore, it appears that HIPVs have potential for use in suppression of Lygus population densities.

Host Plants of the Tarnished Plant Bug (Heteroptera: Miridae) in Central Texas

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has taken on added importance as a pest of cotton in the Cotton Belt after successful eradication efforts for the boll weevil (Anthonomus grandis grandis Boheman). Because the Southern Blacklands region of Central Texas is in advanced stages of boll weevil eradication, blooming weeds and selected row crops were sampled during a 3-yr study to determine lygus species composition and associated temporal host plants. L. lineolaris was the sole lygus species in the region. Thirteen previously unreported host plants were identified for L. lineolaris, of which 69% supported reproduction. Rapistrum rugosum L. Allioni and Ratibida columnifera (Nuttall) Wooton and Standley were primary weed hosts during the early season (17 March to 31 May). Conyza canadensis L. Cronquist variety canadensis and Ambrosia trifida L. were primary weed hosts during the midseason (1 June to 14 August) and late-season (15 August to 30 November), respectively. Sisymbrium irio L. and Lamium amplexicaule L. sustained L. lineolaris populations during the overwintering period (1 December to 16 March). The proportion of females and numbers of nymphs found in R. rugosum, C. canadensis, A. trifida, and S. irio suggests these weeds supported reproductive adults during the early, mid-, and late season and overwintering period, respectively. Medicago sativa L. was the leading crop host for L. lineolaris; Glycine max L. Merrill did not yield L. lineolaris. Few L. lineolaris were collected in Gossypium hirsutum L. These results provide a more comprehensive assessment of host plants contributing to L. lineolaris populations in central Texas.