No. 6 Article 3/May 14, 2010

Trochanter Mealybug: Yet Another New Insect Pest of Soybeans?

In 2008, trochanter mealybug (Pseudococcus sorghiellus) infestations were reported in an issue of the Kentucky Pest News (August 25, 2008, issue 1176) published by the University of Kentucky. This species was first described in 1855 from insects removed from sorghum plants grown in Illinois. Last year, Ron Hammond, an extension entomologist at Ohio State University, reported infestations of mealybugs in some soybean fields where a potassium deficiency was suspected due to the yellow coloration on leaves.

The trocanter mealybug. (Photo courtesy of Ron Hammond, Ohio State University Extension.)

Leaf yellowing associated with mealybug infestation. (Photo courtesy of Ron Hammond, Ohio State University Extension.)

Unlike soybean aphids, trochanter mealybugs are root feeders. However, similarly to soybean aphids, they remove fluids from plant tissue with their piercing and sucking mouthparts. The host range for trochanter mealybugs is large and includes many legumes, such as alfalfa, red clover, white clover, and soybeans. The mealybugs also have been collected from corn, Johnson grass, and sorghum.

Lee Townsend, an extension entomologist with the University of Kentucky, reported (Kentucky Pest News, issue 1178) that in 2008, some red clover plants sampled within pastures had "heavily infested" roots. Illinois producers are encouraged this season to examine roots of soybean plants that appear to have potassium deficiency symptoms (yellowing of leaves). If you find numerous small whitish insects on the roots, please let me know. If I receive numerous reports, a more formal survey may be initiated in the future. At this point, it is unclear whether trochanter mealybugs will emerge as a new management challenge for soybean producers or will remain primarily a curiosity, showing up occasionally in soybean fields with a history of legume production.--Mike Gray

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