Monitoring eastern flower thrips and soybean thrips (Thysanoptera: Thripidae) and the generalist predator, insidious flower bug (Hemiptera: Anthocoridae) in the American Midwest

Authors: LAGOS-KUTZ, DORIS - Illinois Natural History Survey; SEITER, NICHOLAS - University Of Illinois; TILMON, KELLY - The Ohio State University; MCMECHAN, JUSTIN - University Of Nebraska; Hartman, Glen; Clough, Steven; MOLANO-FLORES, BRENDA - Illinois Natural History Survey; CROSSLEY, MICHAEL - University Of Delaware

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Thrip insects can carry plant pathogenic viruses and transmit the viruses to plants while feeding. An example of a plant virus transmitted by thrips to soybean is the soybean vein necrosis virus (SVNV). It would be beneficial to track movement and populations of the thrips (both the Eastern flower thrip and the Soybean thrip) that carry and transmit SVNV, as well as to identify and track any known predators of these thrips. Here we report on our tracking of the Eastern flower thrip and the Soybean thrip, as well as the thrip predator known as the ‘insidious flower bug’ which kills the soybean-feeding thrips. Insects flying across the MidWest were monitored by American Midwest Suction Trap Network between 2020-2023. Associations were made between the timing of early and late activity, cumulative activity density, weather, landscape composition, and host plant phenology. We found that Eastern flower thrips appeared earlier in the season, and later was the insidious flower bug. Soybean thrips and insidious flower bug activity also began earlier in the season potentially reflecting the importance of non-crop host plants in early activity of these insects. Despite the predator becoming active later, soybean thrips ultimately achieved higher cumulative activity later in the season, potentially due migration into soybean growing areas. Our results suggest that local conditions are important to include in models predicting Eastern flower and soybean thrips activity, information that can be helpful to those trying to manage insect populations for optimal soybean yield.

Technical Abstract: Thrips (Frankliniella tritici and Neohydatothrips variabilis) are vectors of soybean vein necrosis virus (SVNV) and have increased in importance since the detection of the SVNV in 2008 in Arkansas. Understanding the factors that influence the timing and extent of these insects’ activity could contribute to improved management, as well as the monitoring of their predators such as the insidious flower bug (Orius insidiosus). Here, we compiled monitoring data between 2020-2023 from the American Midwest Suction Trap Network and examine associations between the timing of early and late activity, cumulative activity density, weather, landscape composition, and host plant phenology. We found that Eastern flower thrips activity began earlier, and late activity of insidious flower bug occurred later when it was warmer. Soybean thrips activity began earlier when there was higher edge density in the landscape but was not coincident with the timing of soybean bloom, potentially reflecting the importance of non-crop host plants in early activity of these insects. Despite becoming active later, soybean thrips ultimately achieved higher cumulative activity density where it was warmer, a discordance potentially reflecting the importance of migration. So, suction trap captures might thus reflect influences of local conditions as well as migratory movements on soybean thrips activity. Soybean thrips and insidious flower bug cumulative activity densities were also found to be positively correlated, suggesting that insidious flower bugs may be opportunistically utilizing soybean thrips as prey and not providing natural suppression. Our results suggest that local conditions are important to include in models predicting Eastern flower and soybean thrips activity.