Economic Productivity and Profitability Analysis for Whiteflies and Tomato Yellow Leaf Curl Virus (TYLCV) Management Options Esendugue Greg Fonsah, Chen, Yu, Stan Diffie, Rajagopal babu Srinivansan, David Riley Abstract The United States is the second largest producer of tomatoes (Lycopersicon esculentum Mill.) in the world. In the U.S. tomato is produced for fresh and processed markets, respectively, and both markets contribute over $2 billion in annual farm cash receipts (Wells, 2012). Tomato yellow leaf curl virus (TYLCV), transmitted by whiteflies, is a major threat to tomato production in the United States and around the world (Polston et al. 1999, Moriones and Navas-Castillo, 2000; Lefeuvre et al., 2010). The spread of the virus in the field is directly correlated to increase in B. tabaci populations (Rakib et al., 2011; Adi et al., 2012). Infected plants display severe symptoms, are less vigorous, and produce fruits with reduced market value. It is common to experience yield losses of up to 100% in affected fields (Rakib et al., 2011; Pan et al., 2012; Wu et al., 2012, Srinivasan et al. 2012). There are several management tactics available. However, there is no single most effective „silver bullet‟ management tactic to manage whiteflies and TYLCV. Therefore, it is vital to integrate several tactics to suppress pest and virus incidences and to boost yields. This study investigates the economic productivity and profitability of combining management options such as insecticides, reflective mulch, and virus-resistant cultivars for whiteflies and TYLCV management. The economic models adopted for this study include farm enterprise budgeting, sensitivity analysis and break-even analysis. Results show that total pre-harvest variable cost was $4,200/ac and the expected net return was $1,958/ac was attainable 50% of the time. Full Text: PDF DOI: 10.15640/jaes.v7n1a1

El proceso de transmision de virus vegetales requiere de la presencia de un insecto vector en al menos el 65% de los casos. Por tanto, la dispersion de estos patogenos en los cultivos esta fuertemente condicionada por el comportamiento de seleccion de hospedador de su correspondiente vector. En los ultimos anos han aumentado los casos que describen alteraciones fenotipicas de la planta producidas tras la infeccion por el virus para atraer o favorecer el desarrollo de estos insectos. Sin embargo, en el caso de Geminivirus transmitidos por mosca blanca no existe un consenso en cuanto a la descripcion de las interacciones virus-planta-vector. Este trabajo se realizo en la Universidad de Georgia (Tifton Campus), una region donde el virus de la cuchara del tomate (Tomato yellow leaf curl virus, TYLCV: Geminiviridae) esta presente desde finales de los anos noventa. El biotipo B de la mosca blanca del tabaco, Bemisia tabaci, es su principal insecto vector en el sureste de Estados Unidos, transmitiendo el virus de manera persistente a la planta de tomate (Solanum lycopersicum L.) en cultivos al aire libre.

Thrips are major crop pests and virus vectors in many parts of the world. Despite their economic importance, thrips diversity in Pakistan is not well documented. Surveys were carried out from year 2009 to 2012 to decipher thrips fauna in Pakistan. A total of 158 sites in three climatic regions were surveyed, and specimens were collected from a wide range of flora. Following taxonomic keys, we identified 12 species from 3 genera of the suborder Tubulifera and 30 species from 17 genera of the suborder Terebrantia. Of these one species (Apterygothrips pellucidus Ananthakrishnan) from Tubulifera and 7 species (Chirothrips meridionalis Bagnall, Chaetanaphothrips orchidii Moulton, Megalurothrips usitatus Bagnall, Megalurothrips distalis Karny, Neohydatothrips samayunkur Kudo, Taeniothrips major Bagnall, Thrips trehernei Priesner) from Terebrantia and four genera (Aptetygothrips, Chaetanaphothrips, Neohydatothrips, Taeniothrips) were first reports from Pakistan. A checklist of species reported in Pakistan since 1947 including those from the current survey was compiled.

Persistent plant viruses, by altering phenotypic and physiological traits of their hosts, could modulate the host preference and fitness of hemipteran vectors. A majority of such modulations increase vector preference for virus-infected plants and improve vector fitness, ultimately favouring virus spread. Nevertheless, it remains unclear how these virus-induced modulations on vectors vary temporally, and whether host resistance to the pathogen influences such effects. This study addressed the two questions using a Begomovirus-whitefly-tomato model pathosystem. Tomato yellow leaf curl virus (TYLCV) -susceptible and TYLCV-resistant tomato genotypes were evaluated by whitefly-mediated transmission assays. Quantitative PCR revealed that virus accumulation decreased after an initial spike in all genotypes. TYLCV accumulation was less in resistant than in susceptible genotypes at 3, 6, and 12 weeks post inoculation (WPI). TYLCV acquisition by whiteflies over time from resistant and susceptible genotypes was also consistent with virus accumulation in the host plant. Furthermore, preference assays indicated that non-viruliferous whiteflies preferred virus-infected plants, whereas viruliferous whiteflies preferred non-infected plants. However, this effect was prominent only with the susceptible genotype at 6 WPI. The development of whiteflies on non-infected susceptible and resistant genotypes was not significantly different. However, developmental time was reduced when a susceptible genotype was infected with TYLCV. Together, these results suggest that vector preference and development could be affected by the timing of infection and by host resistance. These effects could play a crucial role in TYLCV epidemics.

Thrips-transmitted Tomato spotted wilt virus (TSWV) has a broad host range including crops and weeds. In Georgia, TSWV is known to consistently affect peanut, tomato, pepper, and tobacco production. These crops are grown from March through November. In the crop-free period, weeds are presumed to serve as a green bridge for thrips and TSWV. Previous studies have identified several winter weeds as TSWV and thrips hosts. However, their ability to influence TSWV transmission in crops is still not completely understood. To further understand these interactions, population dynamics of two prevalent vectors, viz., Frankliniella fusca (Hinds) and Frankliniella occidentalis (Pergande), on selected winter weeds were monitored from October through April in four counties from 2004 to 2008. Peak populations were typically recorded in March. F. fusca and F. occidentalis adults were found on winter weeds and their percentages ranged from 0 to 68% in comparison with other adults. Immatures outnumbered all adults. Microcosm experiments indicated that the selected winter weeds differentially supported F. fusca reproduction and development. The time required to complete one generation (adult to adult) ranged from 11 to 16 d. Adult recovery ranged from 0.97 to 2.2 per female released. In addition, transmission assays revealed that thrips efficiently transmitted TSWV from peanut to weeds, the incidence of infection ranged from 10 to 55%. Back transmission assays with thrips from TSWV-infected weeds resulted in up to 75% TSWV infection in peanut. These whole-plant transmission and back transmission assays provide the basis for TSWV persistence in farmscapes year round.

Sweetpotato whitefly, Bemisia tabaci (Gennadius), and whitefly-transmitted tomato yellow leaf curl virus (TYLCV) are major threats to tomato production in the southeastern United States. TYLCV was introduced to Florida from the Caribbean islands and has spread to other southern states of the United States. In Georgia, in recent years, the incidence of TYLCV has been steadily increasing. Studies were conducted to monitor population dynamics of whiteflies in the vegetable production belt of Georgia, to evaluate TYLCV-resistant genotypes against whiteflies and TYLCV, and to assess the potential role of resistant genotypes in TYLCV epidemiology. Monitoring studies indicated that the peak incidence of whiteflies varied seasonally from year to year. In general, whitefly populations were not uniformly distributed. Tomato genotypes exhibited minor differences in their ability to support whitefly populations. TYLCV symptoms were visually undetectable in all but one resistant genotype. The infection rates (visually) in susceptible genotypes ranged from 40 to 87%. Greenhouse inoculations with viruliferous whiteflies followed by polymerase chain reaction (PCR) indicated that up to 100% of plants of resistant genotypes were infected, although predominantly symptomless. TYLCV acquisition by whiteflies from TYLCV-infected genotypes was tested by PCR; TYLCV acquisition rates from resistant genotypes were less than from susceptible genotypes. Nevertheless, this difference did not influence TYLCV transmission rates from resistant to susceptible genotypes. Results emphasize that resistant genotypes can serve as TYLCV and whitefly reservoirs and potentially influence TYLCV epidemics.

Thrips-transmitted Iris yellow spot virus (IYSV) (Family Bunyaviridae, Genus Tospovirus) affects onion production in the United States and worldwide. The presence of IYSV in Georgia was confirmed in 2003. Two important thrips species that transmit tospoviruses, the onion thrips (Thrips tabaci (Lindeman)) and the tobacco thrips (Frankliniella fusca (Hinds)) are known to infest onion in Georgia. However, T. tabaci is the only confirmed vector of IYSV. Experiments were conducted to test the vector status of F. fusca in comparison with T. tabaci. F. fusca and T. tabaci larvae and adults reared on IYSV-infected hosts were tested with antiserum specific to the nonstructural protein of IYSV through an antigen coated plate ELISA. The detection rates for F. fusca larvae and adults were 4.5 and 5.1%, respectively, and for T. tabaci larvae and adults they were 20.0 and 24.0%, respectively, indicating that both F. fusca and T. tabaci can transmit IYSV. Further, transmission efficiencies of F. fusca and T. tabaci were evaluated by using an indicator host, lisianthus (Eustoma russellianum (Salisbury)). Both F. fusca and T. tabaci transmitted IYSV at 18.3 and 76.6%, respectively. Results confirmed that F. fusca also can transmit IYSV but at a lower efficiency than T. tabaci. To attest if low vector competency of our laboratory-reared F. fusca population affected its IYSV transmission capability, a Tomato spotted wilt virus (Family Bunyaviridae, Genus Tospovirus) transmission experiment was conducted. F. fusca transmitted Tomato spotted wilt virus at a competent rate (90%) suggesting that the transmission efficiency of a competent thrips vector can widely vary between two closely related viruses.

Iris yellow spot virus (IYSV) can severely affect onion production. IYSV is transmitted by the onion thrips, Thrips tabaci. However, information on IYSV-thrips-onion interactions is limited due to the difficulty associated with infecting onion plants experimentally. Lisianthus (Eustoma russellianum) was used as an indicator host to study mechanical transmission of IYSV, IYSV transmission by T. tabaci, IYSV distribution in the host plant, and the effect of temperature on IYSV symptom expression. Mechanical inoculation tests from IYSV-infected onion plants to noninfected lisianthus plants resulted in a mean transmission rate of 82.5 ± 6.9% (mean ± standard error), and from IYSV-infected lisianthus plants to noninfected lisianthus plants resulted in a mean transmission rate of 89.2 ± 7.1%. T. tabaci adults transmitted IYSV at a rate of 80.0 ± 8.3% from infected onion plants to noninfected lisianthus plants. To assess IYSV distribution in infected lisianthus plants, leaf sections, stems, and roots were tested by enzyme-linked immunosorbent assay (ELISA). All the plant parts tested positive for IYSV, but not on every plant assayed. Alternating night and day temperatures of 18 and 23°C, 25 and 30°C, and 30 and 37°C were evaluated for the effects on IYSV symptom expression. More severe symptoms developed on inoculated plants incubated at the 18 and 23°C or 25 and 30°C temperature regimes than at the 30 and 37°C regime, and symptoms were observed earliest on plants incubated at the 25 and 30°C temperature regime compared to the other temperature regimes.

The onion thrips, Thrips tabaci (Lindeman), is the only known vector of Iris yellow spot virus (IYSV). IYSV was detected in Georgia for the first time in 2003. Phylogenetic analysis using nucleotide sequences of the IYSV capsid gene indicated that it may have been accidentally introduced from repackaging of imported Peruvian onions in the Vidalia onion-growing region. The tobacco thrips, Frankliniella fusca (Hinds), has been the dominant thrips species on onions in Georgia. However, in recent years the incidence of T. tabaci on onions has been consistently increasing. Laboratory competition studies indicated that T. tabaci outcompeted F. fusca on onion foliage. This led to speculation that a new biotype of T. tabaci may have been introduced along with IYSV through importation of Peruvian onions. This hypothesis was tested by analyzing variations in the mitochondrial cytochrome oxidase I gene and internal transcribed spacer region 2 of T. tabaci populations from Georgia and Peru. DNA was extracted from T. tabaci samples from Georgia and Peru and subjected to PCR using specific primers. The resulting amplicons were sequenced. Parsimony and Bayesian analysis of the COI sequences indicated that all the Peruvian taxa fell into a single clade along with one Georgia taxon. All the other Georgia taxa were in a separate clade. ITS2 sequence comparisons indicated that Georgia and Peru taxa were found in numerous clades. High variation among taxa from each region indicated that ITS2 may not be suitable to assess intraspecific variation among T. tabaci populations.

Red Imported Fire Ant colonies were allowed access in the laboratory to eggs of eight reptilian and one avian species. The ants were allowed to forage on the eggs for approximately one week each after which the eggs were removed from the foraging arenas. Evaluations of the impact of fire ant foraging on the eggs were made daily, and final evaluations were made upon removal from the arenas. Red Imported Fire Ants were not able to penetrate healthy Bobwhite Quail eggs, the only avian species used in this trial. The foraging ants were able to penetrate the eggs of Diamondback Terrapins, Yellowbelly Sliders, Eastern Painted Turtles, and Loggerhead Sea Turtles but were not able to penetrate the eggs of Florida Softshell Turtles or Musk Turtles. The ants were able to enter the eggs of Burmese Pythons and Yellow Rat Snakes. Results from this study suggest Red Imported Fire Ants may have a more prominent role in the decline of native reptilian species than was previously thought. Further studies, especially in the field, are necessary to determine the true impact.

A list is presented of 275 species of the Order Thysanoptera known from Florida and 202 species from Georgia; only 122 of these species are from both states. The list was compiled from museum collections, literature reviews, and records of recent introductions. More than 60 exotic species are from the Caribbean basin, with a few recently introduced species from the Oriental region. The lack of available North American faunal information concerning thrips is emphasized (this being derived from haphazard collecting and in only a few areas), as well as the lack of reliable literature for identifying native North American Thysanoptera.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Stan Diffie, Joe Funderburk, Arturo Goldarazena, Laurence Mound; New North American Records for Two Oriental Thrips (Thysanoptera) Species. Journal of Entomological Science 1 January 2008; 43 (1): 128–132. doi: https://doi.org/10.18474/0749-8004-43.1.128 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest Search

The red imported fire ant, Solenopsis invicta Buren, and the black imported fire ant, S. richteri Forel, are reproductively isolated in their native South America even where their ranges overlap (Ross and Shoemaker 2005, Mol. Ecol. 14: 3,419-38). Yet, these invasive ant species readily hybridize in their expanded ranges in North America. Vander Meer and Lofgren (1988, Florida Entomol. 71: 232-32) determined that hybridization occurred in south Alabama soon after the invasion of these ant species. Hybrid ants are morphologically similar to S. richteri and S. invicta, and chemical analysis of ant venom and cuticular hydrocarbons or genetic characterization are required to distinguish hybrid ants from the parent species (Vander Meer et al. 1985, Florida Entomol. 68: 501-06; Ross et al. 1987, Evol. 41: 280-93). Drees et al. (2006, Texas Coop. Ext. B-6043) recently showed S. richteri distributed in only 8 counties in northern Mississippi and 10 counties in west central Tennessee. The S. richteri x S. invicta hybrid, however, is more widely distributed in southern Tennessee, the western tip of North Carolina, and northern areas of Mississippi, Alabama, and Georgia. Although hybridization occurred upon arrival of these two species in North America, S. invicta now occupies the remaining quarantined areas in North America (see http://aphis.usda.gOV) owing to its apparent displacement of S. richteri and the hybrid in this expanded range. Diffie et al. (1988, J. Entomol. Sd. 23: 187-91) initially reported the discovery of the hybrid ant in Alabama and Georgia and mapped its known distribution in Georgia, Alabama and Mississippi. Their survey included ants collected from 20 counties in Alabama and 11 counties in Georgia. The survey reported herein expands those

ENY-845, a 10-page illustrated fact sheet by Joe Funderburk, Stan Diffie, Jyotsna Sharma, Amanda Hodges, and Lance Osborne, describes the common thrips associated with ornamental plants in the southeastern U.S., their biology, feeding behavior and damage, natural enemies, sampling and identification. Includes references and a key representing thrips species from three families. Published by the UF Department of Entomology and Nematology, December 2007.