Project : USDA ARS

ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Systematic Entomology Laboratory » Research » Research Project #438801

Research Project: Systematics of Acari and Hemiptera: Plant Pests, Predators, and Disease Vectors

Location: Systematic Entomology Laboratory

2025 Annual Report

Objectives
New Objective 1: Conduct integrative systematic research of molecular (including Ag100Pest data) and morphological data to: determine species boundaries; recognize, describe, and illustrate new and invasive species; develop identification keys; hypothesize phylogenetic relationships among the respective groups for the purpose of stabilizing classification and providing predictive relationships of species; and investigate host associations and specificity of Acari (mites), Aphidomorpha (aphids), Membracoidea (leafhoppers and treehoppers), Aleyrodomorpha(whiteflies), Coccomorpha (scale insects), and Heteroptera (true bugs) that are pests of or beneficial to U.S. agriculture. [NP304, C1 PS1A; C2 PS2B; C3 PS3A and 3B] New Objective 2: Develop web-searchable electronic databases, tools, and images of mites, aphids, whiteflies, scale insects (Sternorrhyncha), leafhoppers (Auchenorrhyncha), and true bugs (Heteroptera) in the U.S. National Insect and Mite Collection and obtained through field exploration. This includes developing web-based resources to improve technology transfer of research products and disseminating this information to a broad group of stakeholders (e.g., quarantine, conservation, and biological control personnel). The proposed products will include searchable databases and expert systems of certain mites and hemipteran families. [NP304, C1 PS1A; C2 PS2B; C3 PS3A and 3B] New Objective 3: Provide authoritative identifications of specimens submitted by stakeholders worldwide and manage and curate assigned portions of the U.S. National Insect and Mite Collection, including all taxa in the hemipteran suborders Heteroptera, Auchenorrhyncha, Sternorrhyncha, and Coleorrhyncha, which involve more than one and a half million specimens housed in more than 3,000 insect drawers and mounted on hundreds of thousands of microscope slides, and the Acari with more than 360,000 microscope slide containing over a million specimens. [NP304, C1 PS1A; C2 PS2B; C3 PS3A and 3B]

Approach
Morphological characters will be identified through the examination of specimens using dissecting, DIC, Phase Contrast, CLSM, TT-SEM and Cryo SEM. Use of Cryo-SEM in mite taxonomy is revealing remarkable new character systems that were previously unknown and allowing researchers to re-evaluate poorly understood morphological characters that are difficult, if not impossible, to evaluate based on traditional slide-mounted preparations. This technique not only greatly expands the array of morphological characters available, offering them in greater detail, but it also provides valuable behavioral characters, especially with respect to understanding mite feeding behavior. Cryo-SEM will be used to confirm the intricate details of certain morphological characters visible with light microscopy, especially those of the tarsi and empodia. The novel characters available with Cryo-SEM (e.g., tegument texture and tarsal morphology) will be investigated and assessed using a minimum of 5 species from each genus, or more as time and resources permit. The validity of key characters for separating species and genera will be investigated across the family. TT-SEM and CLSM technologies will be used to further the morphological studies. Although the research will focus primarily on morphological and ecological characters of 4 tetranychid genera and 4 eriophyid genera, these data sets will be augmented with molecular data (COI, 18S, 28S, EF-1') as an exploratory avenue for systematic research in these taxa. We will collaborate with Dr. Ashley Dowling and his team at the University of Arkansas who have expertise in molecular characterization of mites. Character information will include the external and internal morphology of mounted flat mites, adults and immatures, combined with the molecular data and analyzed using TNT and MrBayes. Live specimens used for Cryo-SEM studies will be solicited from colleagues and/or brought into the laboratory from domestic and/or foreign fieldwork following standard quarantine regulations and evaluated for morphological characters. In addition, some slide-mounted specimens will be borrowed from or examined at various institutions worldwide, especially the type specimens located in Canada, Brazil and Australia. More than half of the type specimens located at the National Mite Collection (Beltsville, MD) have been studied under DIC and Phase Contrast microscopy. Additional specimens will be collected from regions that are poorly represented in accessible collections, including Australia, South America, India and China. Methods of preparation and preservation will follow those previously described for slide mounting and Cryo-SEM.

Progress Report
In support of Objective 1, a substantial amount of the work on the revisionary study of the jumping tree bugs (Isometopinae) of the Western Hemisphere was completed during this project, with habitus images (dorsal and lateral) and plates completed for nearly 80 species, about half of which are new to science, a significant amount of the manuscript has been completed with descriptions of most of the 40 previously known taxa prepared, the literature has been fully reviewed and compiled, and keys to genera and a key to the 11 species of the tribe Diphlebini, including six of which are new to science, were completed. In addition, a paper on the Indian and Sri Lankan Isometopinae, treating nine genera and 17 species, including six species new to science, has been published, two papers are in preparation, describing six additional species, and currently representatives of all the New World genera are being sequenced, which will help hypothesize relationships within the subfamily. In support of Sub-objective 1.A.2, research on an understudied group of treehoppers continued. At the beginning of this research, this group had only 43 known species. Examining specimens from major museums of North and South America—the native distribution of the group— revealed that there are 500-800 undescribed species. Determining species limits and exact species number is hampered by their solitary nature, resulting in many unassociated males and females. A data matrix of over 50,000 data points for 76 features and of hundreds of feature conditions and 760 morphospecies (estimates of separate species) has been constructed in preparation for an evolutionary study to establish genus and species limits and to develop an online interactive identification key (Sub-objective 2.A.2). Some of the features are taken from the limited previous research on the group, but many are novel features. Additional specimens obtained, including many from Colombia and Brazil, have yet to be included in the dataset. Over 3,340 high resolution photographs have been taken and edited, 400 of them this year. Results of several parts of this project have been published, including a new species from the southeastern United States that is a pest on mulberry. Additional research this year has focused on a project describing the immature stages of New World treehopper genera. Immature stages of insects are often intercepted at ports of entry, so it is vital to be able to identify them. To date, descriptions of immatures have been recorded, most for the first time, with another 36 in two manuscripts near completion. In support of Objective 1, research on the systematics of Aspidiotini armored scale insects continued. Sequencing of nuclear loci is completed for 105 taxa, but complications with amplifying mitochondrial loci delayed progression into the analysis phase. Thus, plans pivoted toward sequencing ultraconserved elements (UCEs) and building a phylogeny based on these data, but a lack of technical support impeded progress. Analysis of aspidiotine phylogeny will be completed after the end of this project cycle. Substantial progress has been made toward estimating a family-level, fossil-calibrated phylogeny of scale insects. Low-coverage genomes have been sequenced for a set of 70 species. A UCE dataset has been assembled from these genome sequences and will be combined with data from an additional 53 species, covering most of the recognized families. A morphological matrix was developed to complement the molecular data matrix for family-level phylogenomic analysis. The dataset comprises 164 taxa and 175 characters. Phylogenomic analysis of these data is anticipated for the summer or fall of 2025. Over the life of the project, disruptions due to the covid-19 pandemic required a shift in focus to objectives that could be completed during a prolonged period of maximum telework. Research achievements included the description of nine new species of armored scales, seven species of root mealybugs, and one fossil scale insect. Additional research identified the origins of the non-native roseau cane scale, a damaging pest of common reed threatening critical infrastructure in the Mississippi River Delta. The results provided focus to biological control efforts and contribute toward the protection and restoration of a critical natural resource and gateway to a major shipping hub in the United States. In support of Objective 2, publications included keys to the species of Aspidiotini armored scales from Argentina and Panama, comprising most of the Central and South American fauna in this tribe, and keys to the newly described species of root mealybugs. Central and South America are common points of origin for agricultural commerce to the United States, and armored scale insects are routinely encountered in plant quarantine from this region. However, comprehensive identification tools for armored scale species from the area are lacking. This research helped to address the knowledge gap and need for resources. In support of Objective 1, research on different mite families was conducted and the results on the main genera and their host associations are scheduled to be published. Successful evaluations of the systematics of the mite genera Cenopalpus, Brevipalpus, Pseudoleptus, Amblypalpus, Aceria, Phyllocoptes, Oziella and Eriophyes and their impact on agriculture and forestry were accomplished. Problems with the cryo-SEM (scanning electron microscopy), including maintenance issues and lack of technical support, affected several collections of specimens and analysis of material. However, using tabletop SEM, we were able to study and compile 80 different eriophyid mite host associations. Further collaboration with the virology team resulted in sequencing viruses carried by some of those mites. Study of the Brevipalpus californicus group resulted in discovery of a complex of 12 species of mites. Their impacts on citrus, orchids, Passiflora, Hibiscus and grasses through transmission of nuclear viruses were documented as well. Furthermore, a key paper on the replication of the virus inside the Brevipalpus mite was published. Research on several invasive flat mite species led to a review of the genus Cenopalpus and resulted in several new records and their impact on forestry. One new genus, seven new species of white mites, and four species of flat mites all associated with ornamentals, fruit trees and timber trees were published. Two new genera with five new species of mites of medical/veterinarian importance were also described. In support of Objective 3, we made 289 urgent and 78 prompt/routine identifications of Heteroptera; 144 urgent and 74 prompt/routine identifications of Auchenorrhyncha; 332 urgent and 296 prompt/routine identifications of Sternorrhyncha; and 408 urgent and 126 prompt/routine identifications of Acari, all as of June 2025. Identifications are provided to support national biosecurity and identify agricultural threats.

Accomplishments
1. Why so many Hemiptera invasions. Hemipterans are the fifth largest order of insects, yet they are tied for first place with beetles as the most invasive pests, costing global agriculture many billions of dollars annually. ARS scientists in Beltsville, Maryland and Washington, D.C., collaborated with a multinational team of experts to find out why hemipteran insects, those that feed on plant sap, are such invasive pests. The team explored reasons for the over-representation of Hemiptera by analyzing geographical, temporal and taxonomic variation in numbers of historical invasions using datasets from 12 world regions. This work identified that key groups, including scale insects and aphids, are responsible for driving over-representation of invasive pests, helping regulatory agencies like USDA APHIS prioritize resource allocation for plant quarantine inspections and justify biosecurity measures that focus on the exclusion of these groups. Invasion success of hemipteran insects is driven by their frequency of transport in trade and by asexual reproduction.

2. Scrub typhus, a new threat on the horizon. Scrub typhus is a mite-vectored disease native to Asia and potentially spreading in the tropical areas. The disease is difficult to diagnose and, when left untreated, can cause mortality in 6% of cases. The potential for scrub typhus to spread to the United States through the introduction of mites that carry the virus is real, and prevention is the best medicine. ARS scientists in Beltsville, Maryland are working with the Smithsonian Institution and experts in Brazil to identify and map the distribution of mites that vector the disease. This knowledge is being used to formulate effective control strategies and provide training to quarantine and medical/veterinary personnel to enhance prevention and responsiveness to these invasive disease vectors.

3. Eriophyid mites, master bioengineers. Eriophyids, also known as bud mites, rust mites, and gall mites, transmit many harmful plant diseases that impact agricultural commodities. A multidisciplinary team of ARS scientists from Beltsville, Maryland and the National Arboretum in Washington, D.C. composed of botanists, virologists, acarologists, and entomologists studied the ecological associations and impacts of these mites. They discovered that eriophyids have co-evolved with and manipulated their host plants’ morphology to favor mite feeding, which in turn transmits many unknown species of viruses in the genus Emaravirus. The eriophyid mites have traditionally been ignored due to their small size and their supposed lack of associated diseases. This discovery is a breakthrough for developing management strategies to prevent plant viral infection and spread, which is estimated to cause $220 billion in losses annually worldwide. Different emaravirus infections have caused major losses in both yield and quality in wheat, roses, and blackberries in the United States, and in pigeonpea, a staple crop in India and neighboring countries. Other emaraviruses may have utility in biocontrol of invasive plants. This information is important for plant protection scientists, farmers, ecologists, and quarantine officers.

4. True bug identification and description. Many true bugs have the potential to damage and cause enormous losses to agriculture annually, whereas a large number of others are predatory and are considered beneficial in controlling arthropod pests. In a series of publications, ARS scientists in Washington, D.C. described two genera and 11 species of true bugs as new to science, all of which are plant feeders. Four of the new species feed on palm trees and four others feed on asters and mints, having the potential of damaging plants in ornamental situations. In addition, an online world catalog was maintained, providing a listing of valid names, distributions, and references to all taxonomic an d biological literature for 4,754 species of the seed bugs, chinch bugs, big-eyed bugs, and their relatives. These resources are used by state and federal regulatory agencies to support crop protection and by scientists conducting research in the fields of agriculture, biocontrol, and systematics.

5. Identifying immature stages of new world treehoppers for quarantine. Except for a few species in the United States, the immature stages of New World treehopper genera are largely unknown. This paucity hampers identification of potentially invasive pests because port interceptions often capture immatures. Based on a unique USDA-ARS collection in the U.S. National Museum of Natural History, built over the last 40 years by an ARS researcher in Washington, D.C., these immatures stages can finally be described, with 36 genera completed so far. These results provide insights into the habits and host plants of the described genera. The new features only present in immatures will be used to enhance phylogenetic studies of treehoppers and the host plant records will be of interest to ecologists.

U.S. DEPARTMENT OF AGRICULTURE

Systematic Entomology Laboratory: Beltsville, MD