Kudzu bug levels in soybeans in the Carolinas continue to be something of a puzzle to entomologists in both states, but the good news is early suggestions for delaying spraying in most cases seems to have been the correct call.
In South Carolina, Clemson Entomologist Jeremy Greene says, “The infestation of kudzu bugs on early-season soybeans continues, but natural mortality of the over-wintered adults is increasing. We might see numbers of this species decline on early-planted soybeans before increasing again when the F1 generation comes off of kudzu.”
Greene says he sprayed some infested soybeans with insecticide several days ago and within a short time observed very high mortality. He used Endigo at 4.5 ounces per acre, but notes that other selected pyrethroid insecticides and pre-mixed products would have done a fine job as well.
As predicted the adult kudzu bugs found on early planted beans don’t seem to have been a major problem, but the egg masses they left behind may be.
On one plant, Greene counted 17 separate egg masses. “These eggs will hatch shortly, and a new generation will be on its way. In my opinion, that will be the generation to worry about,” Greene concludes.
North Carolina State University Entomologist Jack Bacheler says “The colonizing of early planted soybeans by kudzu bugs in Georgia, South Carolina and North Carolina was both a surprise and a wake-up call to check early-planted soybean seedlings for the presence of these pests.”
Bacheler says kudzu bug levels in North Carolina have varied from place to place. “The few soybean fields I swept last week averaged approximately 1 to 2 kudzu bugs per 100 sweeps, certainly well below any threshold that may be established for kudzu bug on early beans.”
On the other hand, Jeff Chandler reported approximately 15-20 bugs per seedling at the field margins and 5 bugs per plant in the center plots of a soybean maturity group and planting date test at the Sandhills Research Station near Jackson Springs, N.C.
Bacheler says he and North Carolina State Entomologist Dominic Reisig agree that 15 or fewer kudzu bugs per 15 sweeps would probably not result in economic damage. However, he says they have no data to support this suggestion.
“We do not recommend routine spraying following the finding of a few kudzu bugs, as this may be of limited economic value and the resulting disruption of beneficial insects can greatly enhance subsequent caterpillar establishment,” Bacheler says.