Soybeans we've seen emerging so far, primarily no-tilled and mainly from planting around April 20, appear green and healthy. Stands appear adequate on most fields so far, but it's still too early to assess what may happen due to weather considerations.
If soybeans turn yellow now or alter, or some other abnormalities appear, it will be time to head to the field to see what insect or disease might be at work.
Mike Gray, a University of Illinois Extension entomologist, advises growers to be on the look-out for what's known as trochanter mealybugs.They are root feeders that remove fluid form plant tissue. Sometimes they may not show up until later in the season.
Gray isn't sounding the alarm, nor is he predicting that this pest with an unusual name will be a new management challenge for most soybean producers from Illinois eastward and to the south. However, infestations of the pest were reported in the Kentucky Pest News newsletter in late August in 2009. And an Ohio State University extension entomologist determined what consultants originally thought was a potassium deficiency causing yellow coloration on soybean leaves was really an infestation of these trochanter mealybugs. No reports have been published from Indiana, as far as is known.
One potential problem could be that this pest has multiple hosts besides soybeans that it can feed upon during the year. It includes alfalfa, red clover, white clover and more, besides soybeans. The pest has even been collected from the roots of corn, johnsongrass and sorghum. So the host range for this pest appears to be quite wide and varied, the entomologist notes.
Early symptoms appear to be yellowing of leaves, the entomologist says. It's actually caused by wheat's happening underground, as the bugs use their piercing and sucking mouthparts to remove fluid from the plant.
Gray suggests reporting any sightings of yellowish leaves on beans to your local Extension educator or corps consultant, especially if the yellowing is not easily explained by another means. He's waiting to see what happens this summer before launching a more exhaustive survey into how widespread or potentially damaging this pest could be to soybeans in the Midwest.
You can learn more now about trochanter mealybugs from an on-line publication from U of I Extension. Find it at: ipm.illinois.edu/bulletin.