Early Season Kudzu Bug Threshold Recommendation

Article by Jack Bacheler:

On the kudzu bug front, the colonizing of early planted soybean by kudzu bug in GA, SC and NC was both a surprise and a wake-up call to check soybean early-planted seedlings for the presence of these pests. Although no treatment thresholds have been established yet for kudzu bugs on early soybeans, sweep net samples taken from representative areas (be careful to avoid field edges) of early soybean fields will at least put producers in the ballpark of whether damaging levels may be present. The few soybean fields that I have swept this 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 (Fig. 4). This is within the area of North Carolina where kudzu bug was found on soybean last fall. Additionally, the images sent out by Jeremy Greene of Clemson last week dramatically showed that kudzu bug levels in some early soybean fields have reached alarming levels during the past two weeks, and more could be coming. Dominic’s and my seat-of-the-pants guess is that 15 or fewer kudzu bugs per 15 sweeps would probably not result in economic damage. However, we presently 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. For the later season anticipated large flight of kudzu bugs into soybean, expected here in late July or early August, the treatment threshold of 15 nymphs per 15 sweeps developed in GA and SC is recommended.

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