Emergence of insect-transmitted plant viruses over the past 10-20 years has been disproportionately driven by two so-called supervectors: the whitefly, Bemisia tabaci, and the Western flower thrips, Frankliniella occidentalis. High rates of reproduction and dispersal, extreme polyphagy, and development of insecticide resistance, together with human activities, have made these insects global pests. These supervectors transmit a diversity of plant viruses by different mechanisms and mediate virus emergence through local evolution, host shifts, mixed infections, and global spread. Associated virus evolution involves reassortment, recombination, and component capture. Emergence of B. tabaci-transmitted geminiviruses (begomoviruses), ipomoviruses, and torradoviruses has led to global disease outbreaks as well as multiple paradigm shifts. Similarly, F. occidentalis has mediated tospovirus host shifts and global dissemination and the emergence of pollen-transmitted ilarviruses. The plant virus-supervector interaction offers exciting opportunities for basic research and global implementation of generalized disease management strategies to reduce economic and environmental impacts.

Role of the Insect Supervectors Bemisia tabaci and Frankliniella occidentalis in the Emergence and Global Spread of Plant Viruses.

Tospoviruses belong to the sole phytovirus genus, Tospovirus , in the family Bunyaviridae . Tospoviruses are known to be exclusively transmitted by thrips belonging to the family Thripidae and subfamily Thripinae. Of the known 1,710 species of Thripidae only 14 thrips species are currently reported to transmit tospoviruses. Thrips-transmitted tospoviruses cause severe yield losses to several economically important crops in the United States and worldwide. For instance, a single Tospovirus ( Tomato spotted wilt virus ) alone caused an estimated $1.4 billion in losses in the U.S. over 10 years. Global trade and associated movement of plant materials across borders have introduced tospoviruses and their vectors into newer areas. Advances in serological and molecular techniques have also led to identification of new tospoviruses. This scenario has also initiated new vector-pathogen interactions between introduced and native thrips species and tospoviruses. The goal of this manuscript is to provide a comprehensive and updated list of thrips species that serve as vectors of tospoviruses along with information pertaining to common names, key diagnostic characters, distribution, important crops economically affected, and thrips and Tospovirus -induced symptoms. The manuscript is prepared with special emphasis to the U.S., but information pertaining to other countries is also included.

Thrips Vectors of Tospoviruses

Virus Diseases of Peanut

In the past 30 years, western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), has become one of the most important agricultural pests worldwide. Certain biological attributes of this insect predispose it to be a direct pest across a wide range of crops. In addition to the direct damage it can cause, this species is an efficient vector of Tomato spotted wilt virus and other Tospoviruses. This review addresses questions regarding the biological and ecological attributes of western flower thrips that have enabled it to become a significant pest and make it so difficult to manage. These important life history traits include western flower thrips polyphagy and a tendency to reside and feed in concealed areas of flowers and fruits. Consequently, large populations can develop and disperse into a wide range of crops. The larvae and adults feed in a similar manner and can share the same host plant resources. The relatively short generation time and haplodiploid sex determination also contribute to the pest status of this species. These life history traits interact in complex ways to make western flower thrips one of the most significant and difficult to manage pests in the world.

https://bioone.org/journals/florida-entomologist/volume-92/issue-1/024.092.0102/Biology-and-Ecology-of-the-Western-Flower-Thrips-Thysanoptera/10.1653/024.092.0102.pdf

Biology and Ecology of the Western Flower Thrips (Thysanoptera: Thripidae): The Making of a Pest

Ants are recognized for their abilities both to engage in mutualistic interactions with diverse taxa, and to invade and dominate habitats outside their native geographic range. Here, we review the effects of invasive ants on three guilds of mutualists: ant-dispersed plants, ant-tended arthropods, and ant-tended plants. We contrast how those three guilds are affected by invasions, how invasive ants differ from native ants in their interactions with those guilds, and how the seven most invasive ant species differ amongst themselves in those interactions. Ant-dispersed plants typically suffer from interactions with invasive ants, a result we attribute to the small size of those ants relative to native seed-dispersing ants. Effects on the ant-tended arthropods and plants were more frequently positive or non-significant, although it is unclear how often these interactions are reciprocally beneficial. For example, invasive ants frequently attack the natural enemies of these prospective mutualists even in the absence of rewards, and may attack those prospective mutualists. Many studies address whether invasive ants provide some benefit to the partner, but few have asked how invasives rank within a hierarchy of prospective mutualists that includes other ant species. Because ant invasions typically result in the extirpation of native ants, this distinction is highly relevant to predicting and managing the effects of such invasions. Interspecific comparisons suggest that invasive ants are poorer partners of ant-dispersed plants than are most other ants, equally effective partners of ant-tended arthropods, and perhaps better partners of ant-tended plants. Last, we note that the invasive ant taxa differ amongst themselves in how they affect these three mutualist guilds, and in how frequently their interactions with prospective mutualists have been studied. The red imported fire ant, Solenopsis invicta, appears particularly likely to disrupt all three mutualistic interactions, relative to the other six invasive species included in this review.

The effects of invasive ants on prospective ant mutualists

Ground-dwelling ant species attracted to four food baits in Georgia.

Thrips are the key arthropod pest of onions in Georgia. Historically, this pest complex has been reported to consist primarily of tobacco thrips, Frankliniella fusca (Hinds), western flower thrips, F. occidentalis (Pergande), and onion thrips, Thrips tabaci Lindeman, with < 1% reported as onion thrips. Onion thrips, however, has become a greater concern in this region because this species is the primary vector of Iris Yellow Spot Virus (IYSV), which was detected in commercial fields in 2003, and both onion thrips and IYSV were detected in culled onions imported from Peru into the Vidalia region in 2003. Surveys were conducted from 2004 through 2010 in commercial onion fields in the 2 primary counties where Vidalia onions are produced to determine whether onion thrips were becoming more prominent within this region. From 2004 through 2006, F. fusca was the predominant pest species collected in this region. Onion thrips were detected and were widely distributed at levels within historical indications. In 20...

Thrips Species Composition on Onions in the Vidalia Production Region of Georgia

Ten releases of Pseudacteon decapitating flies (Diptera: Phoridae), a classical biological control agent of imported fire ants (Hymenoptera: Formicidae) in the southern United States, were made at 8 different sites in Georgia (USA) over a period spanning 2000 - 2012. Intensive monitoring and survey activities were initiated in 2008 to delineate the dispersal and occurrence of the Pseudacteon spp. in the state. Results show that all 159 counties in Georgia have at least 1 species of Pseudacteon; P. curvatus Borgmeier is established 129 of those counties, P. tricuspis Borgmeier is established in 70 counties, and P. obtusus Borgmeier is established in the county in which it was released. Both P. curvatus and P. tricuspis occur together in 39 counties, and all 3 of the Pseudacteon species occur in the 1 county in which all 3 species were released. These results help target supplemental or additional releases of P. tricuspis, P. curvatus, and P. obtusus as well as releases of other candidate Pseudacte...

Stanley K. Diffie

Papers

Thrips Vectors of Tospoviruses

Ground-dwelling ant species attracted to four food baits in Georgia.

Thrips Species Composition on Onions in the Vidalia Production Region of Georgia

Occurrence of Phorid Fly (Diptera: Phoridae) Parasitoids of Imported Fire Ants (Hymenoptera: Formicidae) in Georgia

Georgiaagricultural experiment stations