Two weeks ago, Jack Bacheler posted our early season threshold recommendation for kudzu bug.
In this post, he stated that “…15 or fewer kudzu bugs per 15 sweeps would probably not result in economic damage.”
I have heard of very few places in the state where these densities have been reached. Isolated cases of treatable situations have occurred in geographies as far spread as Lincoln, Moore, Johnston, Onslow and Beaufort Counties.
Here are several reasons why we are standing by this threshold.
First, adults you see in the field now are from those that over-wintered from last year. These have migrated to soybean and are laying eggs.
If you spray only adults, there is a chance that some eggs will hatch into nymphs that can cause you problems later. Based on the pattern of colonization we have seen this year, the major migration of over-wintering adults is probably over.
We are expecting another migration later in the year (late July or early August) that will re-infest soybeans. This migration will likely put many more of our soybean fields at risk than those currently infested.
Secondly, soybeans can tolerate a lot of injury during the vegetative stages. Remember that the already conservative threshold for foliar feeding pests is 30 percent defoliation throughout the canopy until two weeks prior to flowering.
Kudzu bugs are a stress inducing pest. That means you have time to wait, watch, and see what is happening.
Finally, it takes 6-8 weeks for kudzu bugs to develop from egg to adult. Because we think the migration from over-wintering adults is largely over, this means you can be confident that if you turn your back on a field for the weekend, you won’t return to an out-of-control situation on Monday.
We can’t treat kudzu bugs like corn earworm or velvetbean caterpillar.
Check fields weekly with a sweep net to see what develops before making a treatment decision. Be sure to look for the nymphs as well as the adults.