Emily Zobel, Agriculture Agent Associate
University of Maryland Extension, Dorchester County
ezobel@umd.edu
Soybean thrips are a common insect pest species found in soybean across the United States. However, thrips feeding injury rarely causes economic damage since plants easy outgrow it under favorable environmental conditions.
Thrips are small (0.8- 5 mm) slender insects. The larvae are yellow in coloration, and the adults have bands of brown and white across their body, with fringed wings. Adults and larva feed by scraping the cell walls on the underside of leaves until they rupture. The insect then feeds on the exuding sap. Leaves with heavy feeding damage often have a silver or gold dotted look.
Insecticidal treatment is not ordinarily justified unless populations are unusually high and plants are environmentally stressed, due to hot, dry conditions. Fields should be scouted for thrips by checking the middle trifoliolates of 100 random plants. If over 75% of the sampled trifoliolates are damaged, and there is an average of 8 thrips per leaf, treatment may be advisable. If natural enemies are presents or favorable weather is predicted, then treatment is not needed.
