Factors Affecting Population Dynamics of Thrips Vectors of Soybean vein necrosis virus

Abstract

Thrips-infesting soybeans were considered of minor economic importance, but recent evidence of their ability to transmit a newly identified soybean virus, Soybean vein necrosis virus (SVNV), has raised their profile as pests. Season-long surveys were conducted using suction traps to determine the effects of temperature and precipitation on the spatiotemporal patterns of three vector species of SVNV, Neohydatothrips variabilis (Beach) (Thysanoptera: Thripidae) (soybean thrips), Frankliniella tritici (Fitch) (Thysanoptera: Thripidae) (eastern flower thrips), and Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) (tobacco thrips) in soybean fields in Indiana in 2013 and 2014. In addition, soybean fields were surveyed for presence of SVNV in both years. We found that the magnitude and timing of thrips activity varied greatly for the three species. N. variabilis activity peaked in mid-August each year. The peak activity for F. tritici occurred between late-June, and a second peak in activity was observed in early-August, while F. fusca activity remained more or less the same with no peak. There was no gradient in thrips populations from southern to northern locations. This suggests that these insects are not migratory and may overwinter in soil or perennial noncrop host plants and other weed hosts in Indiana. The capture rates of N. variabilis and F. tritici were only related to temperature, and capture rates of F. fusca were not related to either variable. SVNV was first detected in mid-late August, which coincided with the peak of the primary vector, N. variabilis. The virus was not detected earlier in the season despite peaks in F. tritici activity. Our results may be used in weather-based models to predict both thrips dynamics as well as SVNV outbreaks.

Ecological Interactions among Thrips, Soybean Plants, and Soybean Vein Necrosis Virus in Pennsylvania, USA

“…Thrips populations may have declined due to approaching winter temperatures and crop maturity, as thrips feed on the younger and more succulent parts of plants. Our results were similar to Bloomingdale et al [22] and Keough [14], who reported that the soybean thrips were positively correlated with degree days. We did not find any overwintering soybean thrips during soil sampling to accept Bloomingdale et al's [22] assumption that the soybean thrips in the north do not migrate south in the winter and instead overwinter in the north on perennials.…”

“…Chitturi et al [29] monitored soybean thrips (N. variabilis) populations using sticky traps in Alabama, and found that the population of soybean thrips peaked in the third week of June in different counties (Tallassee, Auburn and Headland) in 2015, while in 2016 the maximum population of thrips were observed in first week of July in Tallassee, Auburn and Headland. In Indiana, Keough [14] observed higher N. variabilis numbers in the month of August on soybean crops. A study was conducted to determine effect of soybean vein necrosis virus and thrips infestation on yield reduction in soybeans planted under greenhouse conditions [30].…”

“…This virus is well established in all soybean growing regions of the USA, Canada, and Egypt [7,12,13]. SVNV is transmitted at a very high rate by soybean thrips, Neohydatothrips variabilis (beach), but other thrips species (Frankliniella tritici and F. fusca) can also transmit the virus with reduced transmission efficiency in the United States [9,[14][15][16][17]. In Egypt, Caliothrips phaseoli, Megalourothirps sjostedti, and F. occidentalis transmitted SVNV at a transmission efficiency of, respectively, 6.7, 3.3, and 3.4% under laboratory conditions [13].…”

Vector Competence of Thrips Species to Transmit Soybean Vein Necrosis Virus

“…variabilis , Frankliniella tritici , F. fusca , Frankliniella sp., Thrips tabaci , Phlaeothrips sp., Anaphothrips sp., and Echinothrips sp., Together, N . variabilis , F. tritici , and F. fusca account for nearly 75% of the thrips fauna found on soybean (Keough et al, 2018). Analysis of vector competence in the three thrips species revealed that tobacco thrips ( F. fusca ) and eastern flower thrips ( F. tritici ) are able to transmit SVNV albeit at a lower efficiency (36 and 6%, respectively) compared to the primary vector, soybean thrips (72%) (Keough et al, 2016).…”

The Soybean Aphid Suction Trap Network: Sampling the Aerobiological “Soup”

“…Other insects have been collected routinely in the traps. Suction traps in Indiana in 2013 and 2014 were used to determine the effects of temperature and precipitation on the spatio-temporal patterns of three species of thrips (Thysanoptera: Thripidae) known to be vectors of soybean vein necrosis virus (SVNV): soybean thrips, Neohydatothrips variabilis (Beach); eastern flower thrips, Frankliniella tritici (Fitch); and tobacco thrips, Frankliniella fusca (Hinds) (Keough et al 2018). SVNV detections in mid-to-late August coincided with the peak catch of N. variabilis.…”