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Background: Tobacco thrips, Frankliniella fusca (Hinds), is a pest of cotton. Currently, growers rely on neonicotinoid seed treatments to control F. fusca. However, the occurrence of neonicotinoid-resistant F. fusca populations has created new challenges for their management. Development of thrips-active Cry51Aa2.834_16 Bacillus thuringiensis (Bt) toxin expressed in MON 88702 cotton will be an important new tactic for thrips management. Previous studies have shown that MON 88702 causes limited mortality of F. fusca adults and larvae but reduces infestations on seedling cotton by suppressing oviposition from colonizing adults. This suggests that the toxin affects host preference of adult F. fusca. Knowledge of the effect of this trait on F. fusca feeding behavior provides a more complete understanding of MON 88702 activity. Using electropenetrography, we compared the feeding behaviors of adult F. fusca females on MON 88702 cotton and a non-Bt isoline cotton over 2 h. The number of probes, proportion of probes resulting in ingestion, total duration of ingestion, and duration of ingestion per event were measured., Results: On MON 88702 seedlings, F. fusca probed and ingested fewer times than those on non-Bt cotton. Probes on MON 88702 were less likely to lead to ingestion than on non-Bt cotton. The total duration of ingestion and duration of ingestion per event did not differ between treatments., Conclusion: The results show that MON 88702 has an antifeedant effect on F. fusca, which provides insight into behavioral responses driving MON 88702 aversion and anti-oviposition documented in previous studies. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

Background: Insecticide resistance arises at a given location in response to selection acting on novel genotypes or standing variation, or allelic migration. Fitness costs of resistance may slow resistance evolution or result in reversion to susceptibility, but consistent and geographically widespread use of insecticides may provide sufficient selection to offset the fitness costs of resistance. Understanding this relationship is important to the success of insecticide resistance management. We report the existence of fitness costs of neonicotinoid resistance in field-collected populations of the tobacco thrips (Frankliniella fusca), which increasingly challenge upland cotton production in the southeastern USA., Results: Populations (14 of 15 in 2015; 4 of 5 in 2016) investigated showed a loss of resistance to imidacloprid after multiple generations without exposure to the insecticide. Populations studied in 2016 were each split into two colonies, and one of each pair was repeatedly exposed to imidacloprid. In three of the four populations that lost resistance, imidacloprid-exposed colonies lost resistance significantly more slowly than did corresponding unexposed colonies., Conclusion: For imidacloprid resistance to be broadly increasing in the landscapes of the southeastern USA despite fitness costs of resistance, selection for resistance must be sufficient to overcome the costs. Findings encourage investigation into why costs are overcome in this system, potentially including geographic extent of neonicotinoid use or prevalence of low-dose exposure. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

At-plant applications of insecticides are the most common method to manage thrips in upland cotton, Gossypium hirstutum L. Because the primary pest species, tobacco thrips, Frankliniella fusca (Hinds), has developed resistance to commonly used neonicotinoid insecticides used in producing cotton, alternative control options are needed for sustainable thrips management programs. A 3-year study (2015-2017) showed that densities of thrips, feeding injury from thrips, cotton growth, and yield varied among 10 planting dates. Densities of thrips were lowest in seedling cotton planted after mid-May in all years. Thrips injury ratings in all years were highest in cotton planted in April, lowest in cotton planted in June, and below intermediate injury (intermediate corresponded to a 3 on the 0-5 scale) levels in cotton planted after mid-May. Cotton planted during May, rather than in April or June, had the highest yield potential, regardless of variety. Results of the study indicated that altering planting date could potentially be useful in mitigating injury and losses from thrips in upland cotton., (© The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Spotted wilt caused by tomato spotted wilt virus (TSWV; family Bunyaviridae; genus Tospovirus) is a serious disease of peanut (Arachis hypogaea L.) in the southeastern United States. Peanut genotypes with field resistance to TSWV are effective in suppressing spotted wilt. All commercially available genotypes with field resistance to TSWV were developed through conventional breeding. As a part of the breeding process, peanut genotypes are regularly screened under field situations. Despite numerous advantages associated with field screening, it is often limited by inconsistent vector (thrips) and TSWV pressure. A greenhouse transmission protocol would aid in thorough screening of selected genotypes and conserve time. In this study, various parameters associated with TSWV transmission, including tobacco thrips, Frankliniella fusca (Hinds) density, mode of inoculation, and plant age, were evaluated. Greater incidences of TSWV infection were obtained with thrips-mediated inoculation when compared with mechanical inoculation. TSWV inoculation with three, five, and 10 thrips resulted in greater incidences of TSWV infection in plants than inoculation with one thrips. However, incidences of TSWV infection did not vary between plants inoculated with three, five, and 10 viruliferous thrips. With both thrips-mediated and mechanical inoculation methods, incidences of TSWV infection in 1-wk-old plants were greater than in 4-wk-old plants. TSWV copy numbers, as determined by qPCR, also decreased with plant age. Results suggest that using at least three thrips per plant and 1- to 2-wk-old plants would maximize TSWV infection in inoculated plants., (© The Author 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The Vidalia onion crop in Georgia is grown in the winter, and the key insect pests in Georgia are thrips (Thysanoptera: Thripidae). The thrips complex consists predominantly of tobacco thrips, Frankliniella fusca (Hinds), with smaller percentages of western flower thrips, F. occidentalis Pergande, eastern flower thrips, F. tritici (Fitch) and onion thrips, Thrips tabaci Lindeman. Onion thrips has become a greater concern in the last 10 years likely due to the introduction of a more aggressive biotype of T. tabaci on onions coming from Peru into the Vidalia region. A preliminary laboratory bioassay at 25 °C suggested that this onion thrips biotype could out-compete tobacco thrips on onions. Surveys were conducted from 2004 through 2013 in commercial Vidalia onion fields to determine if this increase in the percentage of onion thrips would occur. Average seasonal temperatures were highly correlated (r = 0.811) with percent T. tabaci and negatively correlated (r = -0.807) with F. fusca. The results suggest that temperature might regulate the proportion of onion thrips to tobacco thrips in the field, with a higher percentage of tobacco thrips occurring during cool winters and more onion thrips occurring in warm winters. Nevertheless, F. fusca continues to be the dominant thrips species in the Vidalia onion winter growing region of Georgia averaging 78% of the adult thrips population from 2004 to 2013. [ABSTRACT FROM AUTHOR]

Phytoviruses including tospoviruses are known to affect the behavior and fitness of their vectors both positively and negatively. In this study, we investigated the effects of Tomato spotted wilt virus ( TSWV) (family Bunyaviridae, genus Tospovirus) infection on the fitness and feeding ability of tobacco thrips, Frankliniella fusca ( Hinds) ( Thysanoptera: Thripidae) using peanut, Arachis hypogaea L. ( Fabaceae), as a host. Potentially viruliferous F. fusca laid more eggs than non-viruliferous F. fusca. In contrast, fewer potentially viruliferous F. fusca developed into adults and required a longer developmental time than non-viruliferous F. fusca, indicating a direct negative effect of the virus on thrips fitness. In addition, no-choice feeding tests indicated that non-viruliferous F. fusca fed more rapidly than potentially viruliferous F. fusca. Typically, phytovirus infections are known to enhance the availability of vital nutrients such as free amino acids in infected host plants and to affect other important physiological processes negatively. Free amino acids are known to play a vital role in egg production and development. Further investigations in this study revealed that leaflets of infected plants had ca. 15 times more free amino acids than non-infected leaflets. TSWV-infected leaflets were used to rear potentially viruliferous thrips. Higher amino acid levels in TSWV-infected leaflets than in non-infected leaflets could have contributed to increased oviposition by potentially viruliferous F. fusca compared to non-viruliferous F. fusca. Taken together, these results suggest that increased concentrations of free amino acids in TSWV-infected plants might serve as an incentive for thrips feeding on otherwise unsuitable hosts, thereby facilitating TSWV acquisition and transmission. [ABSTRACT FROM AUTHOR]

A two-part study related tree pollen dehiscence and thrips population dynamics in the field, and directly evaluated effects of pine pollen deposition on Frankliniella spp. (Thysanoptera: Thripidae) reproduction on tobacco, Nicotiana tabacum L. (Solanaceae), under laboratory conditions. Ambient pollen and thrips were monitored in Tift County, GA, USA, from early spring to late summer/early fall from 2005 to 2008. Correlation analyses were conducted using weekly means of thrips collected on sticky traps compared to weekly pollen counts from a Burkard air sampler and pollen deposition sheets. There were significant positive correlations between pollen and thrips counts on later dates, suggesting that if a relationship exists between pine pollen dehiscence and thrips population dynamics, it will be delayed. Over all years combined, the first spring time peak in Frankliniella fusca (Hinds) counts on sticky traps occurred at 227 accumulated degree days (dd) after the first peak in pine pollen, approximately the dd required to complete a single F. fusca generation. Two subsequent thrips peaks occurred at approximately one and two F. fusca generations following the first peak. After 10 weeks following the final peak in pollen, there appears to be no more effect of pollen on thrips population dynamics. A tobacco leaf, lightly dusted with Slash pine [ Pinus elliottii Engelmann (Pinaceae)] pollen to mimic natural deposition, showed a significant increase in the number of offspring produced per Frankliniella occidentalis (Pergande) and F. fusca female. The total offspring produced increased five-fold in F. fusca and 22-fold in F. occidentalis in 15 days on the pollen-treated leaves over the untreated leaves. [ABSTRACT FROM AUTHOR]

Effects of temperature and precipitation on spring dispersal patterns of Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) caught on yellow sticky traps were estimated in central and eastern North Carolina and eastern Virginia, USA, from 1997 to 2001, and in 2004 and 2007. Data were collected from 44 sites within 14 locations over 7 years, resulting in 30 location-year data combinations. The following independent variables were examined to determine their relationship to the number of F. fusca caught on sticky traps during specified time intervals: cumulative degree days (base 10.5 °C) from 1 November to the start of each trapping interval (DD), number of days with temperatures favorable for flight during each trapping interval (DTFF), and an index of rainfall during specific intervals prior to and during the trapping interval (RI). Regression models that contained various combinations of these variables explained 62, 79, 74, and 68% of the variation in the number of dispersing F. fusca captured during 1–15 April, 16–30 April, 1–15 May, and 16–31 May, respectively. The results provide strong evidence that the suppressive effects of precipitation on growth of local populations developing during late winter and early spring are subsequently manifest at the landscape scale as reductions in the populations of dispersing adults that may persist for as long as 5–6 weeks after the precipitation occurs. [ABSTRACT FROM AUTHOR]

Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) is the predominant thrips species found inhabiting and reproducing in peanut, Arachis hypogaea L. (Fabaceae), and is one of at least seven thrips species reported to transmit Tomato spotted wilt virus (TSWV). The entomogenous nematode Thripinema fuscum Tipping & Nguyen (Tylenchida: Allantonematidae), a natural enemy of F. fusca, parasitizes larval and adult populations under field conditions. All known Thripinema species render the host female thrips sterile and have the potential to suppress pest populations to near extinction. As a result, secondary spread of TSWV in peanut is reduced. Reduction of the virus under field conditions may also be due to lower transmission rates caused by parasite-induced alterations in host feeding behavior. Therefore, the feeding rates of healthy and parasitized F. fusca male and female cohorts on leaf discs were recorded daily for 10 days and digital images were subjected to image analysis and viral transmission rates were compared daily using double antibody sandwich enzyme-linked immunosorbent assay. Thripinema fuscum reduced the feeding of female F. fusca by nearly 65%, and the ability of females to transmit TSWV by 50%. Potential mechanisms underlying the parasite-induced alterations in feeding behavior and transmission are discussed. Parasitism by T. fuscum significantly reduced male longevity, but female longevity was not affected. These results provide further evidence that T. fuscum aids in regulating viruliferous F. fusca pest populations and suggests its potential as a biological control agent for inoculative release in peanut. [ABSTRACT FROM AUTHOR]

Effects of temperature and rainfall timing, amount, and duration on the spread of Tomato spotted wilt virus (Bunyaviridae: genus Tospovirus; TSWV) and population growth of its primary vector, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae), within patches of common chickweed, Stellaria media (L.) Cyrillo (Caryophyllaceae), were examined during the spring of 2004, 2005, and 2006. Elevated temperature treatments were investigated in an attempt to alter the age structure of F. fusca populations and change the effect of precipitation, but an average increase in daily temperature of 1 °C did not increase population size until late spring. Populations of immature F. fusca were immediately and negatively influenced by large amounts of rainfall or by rainfall distributed over three or more consecutive days during late April and early May. However, when precipitation was distributed over 1–3 days during early May, it also delayed senescence of the chickweed and ultimately resulted in a larger F. fusca population late in the season. The majority of TSWV spread within patches of chickweed occurred after mid-April. The fewest TSWV-infected chickweed plants occurred in plots that received high levels of precipitation during April or throughout spring and the amount of spread was directly related to the size of the immature F. fusca population that developed in each plot. [ABSTRACT FROM AUTHOR]

Tree pollen, especially Pinus spp. (Pinaceae), is shed in large quantities every spring in North America. Pine pollen deposition onto leaves was found to significantly influence the ovipositional behaviors of certain thrips species (Thysanoptera: Thripidae) in peanut and tomato leaf choice and no-choice tests. Pine pollen ( Pinus elliottii Engelm.) increased the oviposition rate 2.9-fold for Frankliniella occidentalis (Pergande) (western flower thrips) and 1.6-fold for Frankliniella fusca (Hinds) (tobacco thrips) in choice tests averaged over both plant species. These results support the idea that pollen has a greater impact on F. occidentalis behavior than on F. fusca behavior. The most dramatic increase was in peanut, where F. occidentalis only oviposited on leaves dusted with pollen, suggesting that the addition of pollen stimulated this flower thrips to lay eggs on a poor host-plant part. The impact of pollen on the rate of oviposition by thrips is important because it is the early-instar nymphs that acquire tomato spotted wilt virus (TSWV), which these two thrips species vector. In a laboratory bioassay, the addition of pine pollen to TSWV-infected peanut foliage increased the percentage of infected F. fusca after one generation. [ABSTRACT FROM AUTHOR]

Populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), were shown to differ significantly in their ability to transmit an isolate of tomato spotted wilt virus (Tospovirus: Bunyaviridae) (TSWV) collected from potato [ Solanum tuberosum L. (Solanaceae)]. To gain an understanding of the basis for this variation, we generated reciprocal crosses between an efficient and an inefficient transmitting population. The resulting F1 progeny and progeny from the parental populations were tested for their ability to transmit TSWV. Our results indicate that the ability to transmit TSWV efficiently by T. tabaci is inherited as a recessive trait. [ABSTRACT FROM AUTHOR]

The effects of different isolates of the tomato spotted wilt tospovirus (TSWV), host plants, and temperatures onFrankliniella fusca(Hinds) (Thysanoptera: Thripidae), the most important vector of TSWV in North Carolina, were measured in the laboratory. Thrips were reared at either 18.3, 23.9, or 29.4 °C until adult eclosion on excised leaves ofDatura stramoniumL. orEmilia sonchifolia(L.). Plants were either infected with the TSWV isolates CFL or RG2, or left uninfected (control). The results revealed a positive relationship between larval survival and temperature, regardless of host plant or TSWV isolate. Both survival to adult and percentage transmission of TSWV byF. fuscawere significantly affected by the interaction between host plant and TSWV isolate. The consequence of this interaction was that the cohort-based percentage transmission from infectedE. sonchifoliaplants for CFL was 1.3-fold greater than that of RG2, whereas the percentage transmission from infectedD. stramoniumplants for RG2 was twice that of CFL. Both host plant and TSWV isolates showed significant effects on thrips development time to adult and head capsule width of adult thrips, as well as on the incidence of thrips infection with TSWV. The infection status of these thrips was determined by ELISA for the NSs viral protein. Infected thrips reared on infected host foliage took longer to develop to adult and were smaller than non-infected thrips which had also been reared on infected host foliage, demonstrating a direct effect of the TSWV on thrips. However, non-infected thrips reared on non-infected leaves took longer to develop than non-infected thrips reared on infected leaves, suggesting an effect of the plant tissue on thrips. In addition, adult thrips reared on TSWV-infectedD. stramoniumat 29.4 °C developed smaller head capsules than thrips developing on infected foliage at lower temperatures and on non-infected leaves ofD. stramoniumorE. sonchifolia. Both TSWV isolates and host plants differentially affected females more than males. In conclusion, both the infection of thrips by TSWV and TSWV-mediated changes in host plant quality were found to have significant biological effects onF. fusca. [ABSTRACT FROM AUTHOR]