Page Banner

United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Mite Systematics and Arthropod Diagnostics with Emphasis on Invasive Species

Location: Systematic Entomology

2012 Annual Report


1a.Objectives (from AD-416):
The long-term goal of this project is to produce systematic revisions of monophyletic groups of Acari that are important to U.S. agriculture and transfer this information to stakeholders, scientists, and the general public. The project will focus on the mite families Tenuipalpidae (flat mites) and Tuckerellidae (peacock mites) (both superfamily Tetranychoidea), which are of increasing importance on ornamentals and fruit crops in the U.S. Two flat mite genera, Brevipalpus and Raoiella, are affecting thousands of acres of citrus and palms, respectively, across the U.S. and worldwide; and several species of Brevipalpus are strongly linked with the transmission of serious plant viruses. The peacock mites (genus Tuckerella) cause damage to citrus, avocado, tea, and other ornamental and fruit tree crops. Despite their economic importance, these mite genera are in need of rigorous systematic revision, and the tools available for their identification need improvement. An additional goal is to contribute to the currently minimal understanding of the systematics and classification of these taxa through comparative morphological studies. Over the next 5 years the project will focus on the following objectives: (1) Develop accurate species concepts within mite groups using a holistic approach based on morphological and ecological data; (2) Determine and identify adventive species of mites; (3) Evaluate current taxonomic concepts of mites through discovery of new characters for species separation and subsequent systematic relationships; and (4) Process incoming and outgoing arthropod specimens and identifications, and maintain SELIS (Systematic Entomology Laboratory Identification Service), the on-line identification database about agriculturally important arthropods, for use in quarantine conservation, pest management, and other ARS research programs.


1b.Approach (from AD-416):
Morphological characters will be identified through the examination of specimens using dissecting, Differential Interference Contrast (DIC), Phase Contrast, Confocal microscopes and low temperature scanning electron microscopy (LT-SEM). The novel characters available with LT-SEM will be investigated and assessed using a minimum of 10 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. As part of the data-gathering process, numerous techniques will be used to assess homology and variation in structural characteristics. Measurements and basic statistical data (i.e. range, mean) are often a part of this assessment. Characters will be scored as either discrete or continuous and ordered or unordered, and compiled into a data matrix for analysis. Analyses of the morphological data to construct hypotheses of evolutionary relationships will be conducted using PAUP and MrBayes. MrBayes for Bayesian analyses, and PAUP for parsimony analyses. Although the research will focus primarily on morphological and ecological characters, these data sets will be augmented with molecular data (COI, 18s, 28s, EF-1') obtained from collaborators at the University of Arkansas. Character information will include the external and internal morphology of mounted peacock mites, genus Tuckerella adults and immatures, combined with the molecular data. Identification tools will be developed for users to identify a specific organism among similar organisms and associate a name with that organism. This project will produce traditional dichotomous keys for this purpose, as well as electronic and/or interactive tools that facilitate identifications (e.g., LucID, DELTA). Throughout this project, an additional goal of curating (including remounting and relabelling where needed) and databasing the sections of the collection held in the US National Mite Collection (USNMC) will be met. Mite specimens submitted to the Systematic Entomology Laboratory for identification will be prioritized primarily by importance of their impact, invasive behavior, the number of interceptions, and the commodity involved. The Taxonomic Services Unit is responsible for distributing arthropod specimens submitted for identification to the appropriate SEL research entomologists or collaborators. When the specialists have identified and added their identifications to SELIS, TSU generates a report which is sent to submitters. The TSU coordinates with APHIS, PPQ on a daily basis on various issues relating to identification of specimens intercepted at ports-of-entry or in domestic surveys, especially those specimens with URGENT priority from shipments being detained at ports of entry pending receipt of identification reports from SEL. This objective will result in more than 13,000 identifications (34,000 specimens/year), along with associated biological information, of arthropods annually to customers dependent upon these data for the exclusion of invasive species, assessing potential biological control agents, systematic and biological research, and in support of regulatory programs.


3.Progress Report:
In FY12, we furthered our mite studies on the taxonomy and systematics of the species groups Brevipalpus phoenicis, B. obovatus and B. californicus. The major mite pest affecting the citrus production in the Americas, which is also associated with an important virus family (leprosis virus, nucleotic and cytoplasmatic), is not Brevipalpus phoenicis as has previously been assumed, but is in fact a formerly synonymized species. We are working on the redescription of both species and associated diagnostics. Further confusing host and distribution records for these species is the fact that mites in the group B. obovatus have been regularly misidentified in the group B. phoenicis.

We worked on the genus Raoiella and obtained samples from most of the countries with recorded species. We were able to obtain Raoiella specimens from Greece and recollected R. australica from the type location.

We completed research on the status of Tuckerella japonica in the U.S. and its association with tea around the world, with the submission of a manuscript outlining several new distribution and host records.

We completed Part 1 of a web-based interactive Lucid key for the flat mite family, Tenuipalidae. The flat mite lucid key was tested by several internal and external users and is now available to the national and international community. We were able to collect Tuckerellidae and Tenuipalpidae material from Australia, Brazil, Greece, Argentina, and the U.S. A total of 4 publications addressing plant feeding mites and mite morphology were published in refereed journals.

We are continuing the development of our LucID project for mites, with continued research on improving diagnostics for Brevipalpus and the genus Tenuipalpus, incorporating material intercepted at ports-of-entry or as part of important in plant protection programs.

We are continuing the study of mites using Low Temperature Scanning Electron Microscopy, as such images are key to understanding some important tenuipalpid mite morphological characters (including species in the genera Brevipalpus, Tenuipalpus, Tuckerella, and Raoiella) and other economic important prostigmatid mites (families Tarsonemidae, Penthaleidae, Eriophyidae, and Tetranychidae).


4.Accomplishments
1. Systematic studies of plant feeding mites in the families Tenuipalpidae and Tuckerellidae. Several species of mites in the genera Brevipalpus, Raoiella and Tuckerella are economically important on fruit trees, ornamental and crop plants. The red palm mite (RPM), Raoiella indica Hirst has been identified as one of the major arthropod pest problems on palms. We discovered that RPM feed only via the stomata and based on our findings we were able to indicate why these mites do not attack the native palmetto palms in the genus Sabal. We were able to show that it is not only RPM that feeds via the stomata, but also the entire genus feeds in the same manner, including species on dicot hosts including olive, eucalyptus, water apple and other related tree species. The feeding technique present in the genus Raoiella forces us to question the way we see the mite family and their host plant associations. Collection of Tuckerella specimens had been curtailed due to budgetary constraints in the past and present fiscal years. The species Brevipalpus phoenicis is considered to be one of the most important mite pest species affecting Citrus across the world. However, studying material from Europe, South America, Australia, and the U.S. we discovered that B. phoenicis has been regularly misidentified, and in fact the most common species on citrus is actually another species that had been wrongly synonymized with B. phoenicis. This information is essential in the study, management and control of mite pest on crops by farmers, quarantine specialist, extension agents, state, and university researchers.

2. Mite and insect identification services. The Taxonomic Support Unit (TSU) provides identifications and information on important mite and insect invasive and adventive species. Requests for support come from many sources including APHIS, State Departments of Agriculture, and universities in the U.S. In FY 2012, the mite section identified 387 lots with 2,395 mite specimens. The TSU for FY12 identified 9,892 lots with 25,015 arthropod (insect and mite) specimens. It is reasonable to assume that the rate of IDs will remain constant for the rest of this FY12. If so, these numbers represented 75% of the total expected for this year.


Review Publications
Dowling, A.G., Ochoa, R., Beard, J.J., Welbourn, W.C., Ueckermann, E.A. 2011. Phylogenetic investigation of the genus Raoiella (Prostigmata: Tenuipalpidae): Diversity, distribution, and world invasions. Experimental and Applied Acarology. 57(3-4):257-269.

Kane, E.C., Ochoa, R., Erbe, E.F., Mathurin, G. 2012. Raoiella indica Hirst (Acari: Tenuipalpidae): An island-hopping mite pest in the Caribbean. Revista Manejo Integrado de Plagas. 57(3-4):215-255.

Beard, J.J., Ochoa, R., Bauchan, G.R., Welbourn, W.C., Pooley, C.D., Dowling, A.G. 2012. Flat mite mouthparts and feeding: Raoiella a case study (Tetranychoidea: Tenuipalpidae). Experimental and Applied Acarology. 57(3-4):227-255.

Last Modified: 4/21/2014
Footer Content Back to Top of Page