Use of Molecular Gut Content Analysis to Decipher the Range of Food Plants of the Invasive Spotted Lanternfly, Lycorma delicatula

Unveiling the diet of two generalist stink bugs, Halyomorpha halys and Pentatoma rufipes (Hemiptera: Pentatomidae), through metabarcoding of the ITS2 region from gut content

BACKGROUND

The use of DNA metabarcoding has become an increasingly popular technique to infer feeding relationships in polyphagous herbivores and predators. Understanding host plant preference of native and invasive herbivore insects can be helpful in establishing effective integrated pest management (IPM) strategies. The invasive Halyomorpha halys and native Pentatoma rufipes are piercing-sucking stink bug pests that are known to cause economic damage in commercial fruit orchards.

RESULTS

In this study, we performed molecular gut content analysis (MGCA) on field-collected specimens of these two herbivorous pentatomids using next-generation amplicon sequencing (NGAS) of the internal transcribed spacer 2 (ITS2) barcode region. Additionally, a laboratory experiment was set up where H. halys was switched from a mixed diet to a monotypic diet, allowing us to determine the detectability of the initial diet in a time series of ≤3 days after the diet switch. We detected 68 unique plant species from 54 genera in the diet of two stink bug species, with fewer genera found per sample and a smaller diet breadth for P. rufipes than for H. halys. Both stink bug species generally prefer deciduous trees over gymnosperms and herbaceous plants. Landscape type significantly impacted the observed genera in the diet of both stink bug species, whereas season only had a significant effect on the diet of H. halys.

CONCLUSION

This study provides further insights into the dietary composition of two polyphagous pentatomid pests and illustrates that metabarcoding can deliver a relevant species-level resolution of host plant preference. © 2024 Society of Chemical Industry.

Evaluation of insecticide residues against spotted lanternfly (Hemiptera: Fulgoridae)

Lycorma delicatula White (Hemiptera: Fulgoridae), spotted lanternfly, is a univoltine, phloem-feeding, polyphagous and invasive insect in the United States. Although a primary host for this species is Ailanthus altissima (Mill.) Swingle, tree of heaven, L. delicatula also feeds on many other plant species, including cultivated grapevines. As this species continues to spread, it is important to develop effective management tools. Here, we evaluated the residual efficacy of 4 insecticides commonly used in tree fruit management programs: dinotefuran, bifenthrin, carbaryl, and thiamethoxam. First, all mobile life stages (early instars, late instars, and adults) of L. delicatula were exposed for 1 h to dry insecticide residues (18 h old) applied to glass or A. altissima bark surfaces. While some mortality was detected immediately following the 1 h exposure period, 100% mortality occurred within 24 h for all materials and life stages exposed on both glass and bark surfaces. To evaluate longer residual activity of these materials, groups of adult L. delicatula were introduced into cages containing A. altissima trees treated with the same individual insecticides and exposed 6 h to residues that were 18 h or 7 days old. Paired, untreated A. altissima served as controls. In these bioassays, 48 h mortality for 18 h old residue reached 95% for thiamethoxam and 100% for bifenthrin and dinotefuran. Seven-day-old bifenthrin and dinotefuran residues again yielded 100% mortality, while thiamethoxam resulted in 58% mortality, and carbaryl yielded only 13.3% and was not significantly different from the control. These results clearly document the efficacy of specific insecticide applications as management tools against L. delicatula.

Detection of Ochyromera ligustri (Coleoptera: Curculionidae: Curculioninae) in Ligustrum spp. (Oleaceae) Using Newly Developed PCR Primers

Ligustrum spp. (Oleaceae) have become invasive species in the US and negatively affect native plant diversity and richness in forests. Ochyromera ligustri (Coleoptera: Curculionidae) is considered a potential biological control agent in the US because adults feed on the foliage and larvae are seed-feeders of Ligustrum spp. To discover the relationships between O. ligustri and Ligustrum spp., fruit dissections or rearing and field observations are required. In the current research project, novel PCR primers were developed to rapidly detect the DNA of O. ligustri in molecular analyses without rearing and observation. The developed PCR primers worked even with 0.01 ng of DNA and did not amplify the DNA of the other five curculionid species tested. When the novel primers were tested with three Ligustrum spp. species common in the southeastern US, the DNA of O. ligustri was detected from all three species. We expect that the novel primers will be utilized to find out the presence and impact of O. ligustri on Ligustrum spp rapidly and accurately.

The aphid Myzus persicae (Hemiptera: Aphididae) acquires chloroplast DNA during feeding on host plants

Aphids (Hemiptera: Aphididae) extract nutrients from host plant phloem via stylets that facilitate salivation and sap uptake. When navigating to the phloem, aphids periodically puncture nonvascular cells and sample cell contents, but rarely cause significant cell damage. As a result, aphids are considered "stealthy" feeders. In contrast, insects that do cause damage, such as chewing herbivores, will take up host cell contents-including DNA-into their guts. Researchers can use molecular barcoding methods to identify recent host use patterns of chewing herbivores. This information is valuable for both pest management and basic ecological studies. Because of their stealthy feeding style, it was assumed that host plant DNA could not be recovered from aphids and other Sternorrhyncha. However, several recent studies document host plant DNA uptake by psyllids, which feed in a similar manner to aphids. Therefore, we hypothesized that aphids may also acquire DNA from host plants. Since aphids puncture and sample cytosol contents from cells, we predicted that aphids would be most likely to acquire DNA from chloroplasts. To test this, we performed host feeding and host transfer experiments with Myzus persicae (Sulzer), then used PCR to recover and sequence a region between the trnT and trnF genes from acquired chloroplast DNA. We found that M. persicae readily acquires chloroplast DNA, even prior to phloem contact, and that fragment sizes sufficient for host plant identification can be recovered. Our work suggests that molecular gut content analysis is a viable tool for studying aphid-host interactions.

Evaluating deployment strategies for spotted lanternfly (Lycorma delicatula Hemiptera: Fulgoridae) traps

The spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae), is an invasive planthopper that was first detected in the United States in Berks County, PA, in 2014, and has since spread to 13 states in the Eastern United States. This phloem-feeding pest has a broad host range, including economically important crops such as grapevine, Vitis spp. Monitoring presence and relative abundance of L. delicatula is essential to develop pest management tools. Here, we compared deployment strategies to optimize use of L. delicatula monitoring traps. Standard circle traps, sticky bands, and circle traps with replaceable bag tops were deployed at sites with either high or low populations present. Trap deployment at different heights and on different host tree species and trap sampling intervals were evaluated for standard circle traps only. Circle traps captured significantly more L. delicatula adults at low-density sites compared with other trap types in 2021, and no differences were detected at high-density sights. Traps deployed 1 m from the ground captured significantly more adults than those deployed at 0.5 m; no differences were detected for nymphs. While no significant differences in captures were found among intervals, weekly or biweekly sampling prevented specimen degradation. Although traps deployed on Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae) captured significantly or numerically more L. delicatula at most sites, traps deployed on other hosts also yielded consistent captures. We were also able to alter the construction of circle trap skirts to allow for deployment on different sized tree trunks.

Survival and development of Lycorma delicatula (Hemiptera: Fulgoridae) on common secondary host plants differ by life stage under controlled conditions

Host range assessment for emerging invasive insects is a vital step toward fully defining the issues the insect may pose. Spotted lanternfly (SLF) is an invasive species that is rapidly expanding its presence in the United States. The primary hosts facilitating this spread are tree of heaven, a plant from SLF's native range, and the economically important winegrape. Black walnut is also implicated as an important and common host plant. This study investigated the survival and development of SLF on diets that included a variety of crop host plants in the presence or absence of tree of heaven. The following plant species, 'Honeycrisp' apple, 'Reliance' peach, silver maple, and tree of heaven were paired with winegrape or black walnut throughout the study. SLF had strong development and high survival on a diet of winegrape alone, and winegrape or black walnut paired with tree of heaven. Survival parameters were reduced with all other plant pairings. In particular, SLF in the winegrape and peach diet treatment did not develop past the third nymphal instar. A second experiment evaluated the survival of early and late instar nymphs and adult SLF life stages on three specialty crops - 'Cascade' hops, muscadine grapes, and kiwifruit over a two-week period. Nymphs survived longer than adults, with survival of first and second instar nymphs on hops not differing from the control tree of heaven treatment. The adult stage survived best on kiwi and muscadine grape. Our results show tree of heaven and winegrape were the only single plant diets evaluated that are sufficient for complete SLF development, while other host plants may require additional host or hosts of sufficient nutritional quality for SLF survival.

Biology and Management of the Spotted Lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), in the United States

Spotted lanternfly, Lycorma delicatula (White), invaded the eastern United States in 2014 and has since caused economic and ecological disruption. In particular, spotted lanternfly has shown itself to be a significant pest of vineyards and ornamental plants and is likely to continue to spread to new areas. Factors that have contributed to its success as an invader include its wide host range and high mobility, which allow it to infest a wide range of habitats, including agricultural, urban, suburban, and managed and natural forested areas. Management is dependent on chemical use, although no single currently available control measure alone will be sufficient.

Prolonged phloem feeding by the spotted lanternfly, an invasive planthopper, alters resource allocation and inhibits gas exchange in grapevines

Spotted lanternfly (Lycorma delicatula White; SLF) is a phloem-feeding planthopper invasive to the Eastern United States that can feed on a range of wild and cultivated plant species. Since its 2014 introduction in the United States, large infestations and subsequent economic damage have been reported in cultivated grapevines, but no studies have detailed grapevine physiological responses to SLF phloem feeding. This study investigated grapevine-SLF interactions, detailing how different infestation densities affect leaf gas exchange and end-season concentrations of nonstructural carbohydrates and nitrogen in vegetative and perennial tissues of two Vitis species. Effects on fruit ripeness parameters and dormant bud freeze tolerance were examined, in addition to other year-after effects. Phloem feeding by low densities (≤4 SLF shoot^-1) had minimal effects, whereas greater densities (5-15 SLF shoot^-1) increasingly affected carbohydrate and nitrogen dynamics in both Vitis species. Phloem feeding substantially affected starch and, to a lesser extent, total nitrogen concentrations of woody roots. Prolonged exposure strongly reduced leaf gas exchange. We conclude that intensive late-season phloem feeding by large adult SLF population densities (≥8 SLF shoot^-1) can induce carbon limitation, with the potential for negative year-after effects in cases of severe belowground carbon depletion. This work presents novel insights into SLF-grapevine interactions, identifies avenues of future SLF-plant research, and assists the development of action thresholds for SLF management in vineyards.

Complete genome analysis of a novel iflavirus from the spotted lanternfly Lycorma delicatula

The spotted lanternfly (Lycorma delicatula) is an invasive pest that causes serious economic losses in fruit and wood production. Here, we identified a novel iflavirus named "Lycorma delicatula iflavirus 1" (LDIV1), in a spotted lanternfly. The full genome sequence of LDIV1 is 10,222 nt in length and encodes a polyprotein containing a picornavirus capsid-protein-domain-like domain, a cricket paralysis virus capsid superfamily domain, an RNA helicase domain, a peptidase C3 superfamily domain, and an RNA-dependent RNA polymerase (RdRp) domain. LDIV1 replicates in the host insect and activates small interfering RNA (siRNA)-based host antiviral immunity. Phylogenetic analysis demonstrated that LDIV1 is most closely related to an unspecified member of the order Picornavirales, with 61.7% sequence identity in the RdRp region and 57.6% sequence identity in the coat protein region, and thus meets the demarcation criteria for new species in the genus Iflavirus. To the best of our knowledge, LDIV1 is the first virus discovered in L. delicatula.

Diverse Host Plants of the First Instars of the Invasive Lycorma delicatula: Insights from eDNA Metabarcoding

Identification of host plants of the invasive spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), has been the focus of many studies. While the adults and late nymphs are relatively easy to observe on plants and to use for molecular gut-content analysis, studying the early instars is more challenging. This study is the continuation of our ongoing efforts to determine the host range for each developmental stage of L. delicatula. In the present study, we focused exclusively on the first nymphal instars, and we used a novel approach, utilizing "bulk" DNA extracts for DNA metabarcoding of nymphal gut contents, to identify all the detectable plants that the nymphs had ingested prior to being collected. We were able to obtain high-quality amplicons (up to 406 bp) of a portion of the rbcL gene and detect 27 unique ingested plant species belonging to 17 families. Both native and introduced plants with the prevalence of trees and grasses were present among the ingested plants. We also identified 13 novel host plants that have not been previously reported for L. delicatula on the U.S. territory. The results from our study have important applications for developing effective programs on early monitoring of invasive L. delicatula.

Spotted lanternfly predicted to establish in California by 2033 without preventative management

Models that are both spatially and temporally dynamic are needed to forecast where and when non-native pests and pathogens are likely to spread, to provide advance information for natural resource managers. The potential US range of the invasive spotted lanternfly (SLF, Lycorma delicatula) has been modeled, but until now, when it could reach the West Coast’s multi-billion-dollar fruit industry has been unknown. We used process-based modeling to forecast the spread of SLF assuming no treatments to control populations occur. We found that SLF has a low probability of first reaching the grape-producing counties of California by 2027 and a high probability by 2033. Our study demonstrates the importance of spatio-temporal modeling for predicting the spread of invasive species to serve as an early alert for growers and other decision makers to prepare for impending risks of SLF invasion. It also provides a baseline for comparing future control options.

Process-based modelling reveals the predicted spread of the invasive spotted lanternfly to California by 2033 without controlled management.

Survivorship and Development of the Invasive Lycorma delicatula (Hemiptera: Fulgoridae) on Wild and Cultivated Temperate Host Plants

The invasive spotted lanternfly, Lycorma delicatula, (White Hemiptera: Fulgoridae) continues to spread throughout the Eastern United States. This species exhibits a broad host range, with tree of heaven, Ailanthus altissima (Mill.) Swingle, commonly referred to as the preferred host. Here, we evaluated 2-wk survivorship of early nymphal instars, late nymphal instars, and adult L. delicatula on single diets of ten wild and cultivated hosts: tree of heaven; apple, Malus domestica; peach, Prunus persica; black cherry, P. serotina Ehrh; black locust, Robinia pseudoacacia L.; black walnut, Juglans nigra L.; common hackberry Celtis occidentalis L.; mulberry Morus alba L.; sugar maple Acer saccharum Marshall; white oak, Quercus alba L.. Among them, early and late instars had significantly greater survivorship on tree of heaven and black walnut and adults had greatest survivorship on tree of heaven. Additionally, we evaluated development and survivorship of L. delicatula from newly hatched nymphs to adulthood on single diets of tree of heaven, black walnut, grapevine, apple, and peach, and mixed diets of tree of heaven plus one other host. Single host diets that supported L. delicatula development to adulthood were tree of heaven and black walnut. Interestingly, mixed diets also supported development, and reduced development time to adults by up to 12% compared with the single tree of heaven diet. Our results suggest that within agroecosystems and across landscapes, L. delicatula can develop on single hosts such as tree of heaven, but also on multiple host plants, yielding adults earlier in the growing season.

Ecology and genetic structure of the invasive spotted lanternfly Lycorma delicatula in Japan where its distribution is slowly expanding

Lycorma delicatula has expanded its distribution from China to Japan, Korea, and the USA, causing significant economic damage to vineyards in the latter two countries. However, in Japan, L. delicatula has long been limited to the Hokuriku region, central Japan, and no significant damage to crops has been reported since it was first reported there in 2009. Manipulation experiments and field observations in the Hokuriku region, where winter precipitation is extremely high, revealed that egg numbers and hatchability were significantly reduced in exposed places, especially when wax was excluded from the egg mass. Phylogenetic analysis showed that the population in Japan could be divided into at least two groups. Most L. delicatula samples from Hokuriku formed a clade with those from northwestern China. Samples from Okayama, where the distribution of L. delicatula was recently confirmed, had the same haplotype as those from central China, Korea, and the USA. These results suggest that environmental factors and genetic characteristics of L. delicatula are involved in the relatively slow expansion of its distribution in Hokuriku. Conversely, in Okayama, where precipitation is relatively low, the rapidly increasing haplotype in Korea and the USA was detected, leading to concerns that its distribution will expand further.

Choosing an Effective PCR-Based Approach for Diet Analysis of Insect Herbivores: A Systematic Review

Identification of ingested plant species using polymerase chain reaction (PCR)-based methods is an increasingly useful yet challenging approach to accurately determine the diet composition of insect herbivores and thus their trophic interactions. A typical process of detection of DNA of ingested plants involves the choice of a DNA extraction method, a genomic target region, and/or the best approach for an accurate plant species identification. The wide range of available techniques makes the choice of the most appropriate method for an accurately and timely identification of ingested plants from insect guts difficult. In our study, we reviewed the commonly used PCR-based approaches in studies published from 1977 to 2019, to provide researchers with the information on the tools which have been shown to be effective for obtaining and identifying ingested plants. Our results showed that among five insect orders used in the retrieved studies Coleoptera and Hemiptera were prevalent (33 and 28% of all the records, respectively). In 79% of the studies a DNA barcoding approach was employed. In a substantial number of studies Qiagen DNA extraction kits and CTAB protocol were used (43 and 23%, respectively). Of all records, 65% used a single locus as a targeted plant DNA fragment; trnL, rbcL, and ITS regions were the most frequently used loci. Sequencing was the dominant type of among DNA verification approaches (70% of all records). This review provides important information on the availability of successfully used PCR-based approaches to identify ingested plant DNA in insect guts, and suggests potential directions for future studies on plant-insect trophic interactions.

Host Plant Signal Persistence in the Gut of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae)

Determining the host range of an invasive insect in a new environment is a key step in the development of management strategies. As the brown marmorated stink bug, Halyomorpha halys Stål, expands into agricultural regions of North America, efforts to elucidate its dietary habits on a landscape scale rely on intensive sampling of potential host plants. Although this approach yields useful information, results can be biased toward common and easily sampled plant species; important hosts can be missed if sampling them is impractical or limited in scope. Here we lay the groundwork for the application of gut content analysis to the feeding ecology of H. halys by investigating the persistence of host plant DNA in the digestive tracts of insects with known feeding histories. Adult H. halys were fed bean seedlings (Phaseolus lunatus L.) for 7 d, followed by a forced host switch to carrot (Daucus carota L.). Insect guts were dissected out at 0, 1, 3, 7, and 14 d following the switch, and host plant chloroplast genes (trnF and trnL) were amplified via polymerase chain reaction. Amplicons were identified using high-throughput sequencing and analyzed for Phaseolus DNA. The original host remained detectable at 3 d (trnF) and 14 d (trnL) in substantial quantities. The proportion of total reads identified as Phaseolus rapidly decreased with time; a concomitant increase in Daucus reads was observed. Our results indicate that high-throughput sequencing of gut contents has great potential for exploring the dietary histories of field-caught H. halys and other phytophagous insects.

Detecting Ingested Host Plant DNA in Potato Leafhopper (Hemiptera: Cicadellidae): Potential Use of Molecular Markers for Gut Content Analysis

Detection of host plant DNA from sap-feeding insects can be challenging due to potential low concentration of ingested plant DNA. Although a few previous studies have demonstrated the possibility of detecting various fragments of plant DNA from some sap-feeders, there are no protocols available for potato leafhopper, Empoasca fabae (Harris) (Hemiptera: Cicadellidae), a significant agricultural pest. In this study we focused on optimizing a DNA-based method for host plant identification of E. fabae and investigating the longevity of the ingested plant DNA as one of the potential applications of the protocol. We largely utilized and modified our previously developed PCR-based method for detecting host plant DNA from grasshopper and the spotted lanternfly gut contents. We have demonstrated that the trnL (UAA) gene can be successfully utilized for detecting ingested host plant DNA from E. fabae and determining plant DNA longevity. The developed protocol is a relatively quick and low-cost method for detecting plant DNA from E. fabae. It has a number of important applications-from determining host plants and dispersal of E. fabae to developing effective pest management strategies.

The state of Canada’s biosecurity efforts to protect biodiversity from species invasions

Invasive alien species (IAS) pose threats to native biodiversity globally and are linked to numerous negative biodiversity impacts throughout Canada. Considering the Canadian federal government’s commitments to environmental stewardship (e.g., the Convention on Biological Diversity), the successful management of IAS requires an understanding of how federal infrastructure, strategies, and decisions have contributed to previous outcomes. Here, we present an analysis of current efforts by the federal government to prevent IAS establishment in Canadian ecosystems and the unique challenges associated with Canadian IAS management. We then examine historical and current case studies of IAS in Canada with variable outcomes. By drawing comparisons with IAS management in the United States, Australia, and New Zealand, we discuss how the Canadian government may refine its policies and practices to enable more effective responses to IAS threats. We conclude by considering how future interacting stressors (e.g., climate change) will shape how we address IAS threats, and list six lessons for successful management. Most importantly, Canada must regard biodiversity impacts from IAS with as much urgency as direct economic impacts that have historically garnered more attention. Although we focus on Canada, our findings may also be useful in other jurisdictions facing similar challenges with IAS management.

Worldwide Feeding Host Plants of Spotted Lanternfly, With Significant Additions From North America

The spotted lanternfly Lycorma delicatula (White) is an invasive insect spreading throughout southeast Asia and eastern North America. The rapid spread of this species is facilitated by the prevalence of its preferred host, tree of heaven (Ailanthus altissima (Mill.) Swingle), as well as its use of many other host plants. While the spotted lanternfly has been previously reported to use over 65 plant species, most of these reports are from Asia and may not be applicable in North America. Additionally, many of the known hosts have not been specified as feeding hosts or as egg laying substrates. To better understand the potential impacts of this invasive insect on natural and cultivated systems in North America, we reviewed records from published and unpublished results and observations of host plant use by spotted lanternfly. We aggregated 172 host plant records worldwide and found feeding behaviors associated with 103 plant taxa across 33 families and 17 orders, 20 of which were not previously known to be associated with SLF and 15 of which were not confirmed as feeding hosts. North American records account for 56 of these taxa which include native, cultivated, and nonnative species. As a result, the spotted lanternfly has the potential to impact a wide assortment of ecosystems throughout its potential range and its North American distribution may not be limited by the presence of tree of heaven.