While September is a time when most cotton fields are no longer vulnerable to insect damage, this month can be a different story for soybean producers.
Our generally high 2012 levels of green and brown stink bugs can translate into possible damage to soybean fields that are still filling out pods – that’s much of our acreage. In tests at Rocky Mount, where several planting date and maturity groups were evaluated for insect damage, stink bugs have remained well below threshold levels; this has also been the case at all of our kudzu bug test sites. Of course this might not be the case in other areas.
In our kudzu bug insecticide screening test in Randolph County, the nymph levels in the untreated plots averaged 103.5 per 25 sweeps, or approximately 4 per sweep at 7 days after treatment, in line with the 3-day evaluation. This is more than 4 times the threshold of 1 nymph per sweep or 15 per 15 sweeps, and suggests that other fields in this part of the state and elsewhere may also be at threshold.
A number of treatments containing either bifenthrin or lambda-cyhalothrin showed between 99 and 100 % control of nymphs and similar control of adults. On the return trip to Raleigh, only one field out of the 6 where I stopped to sweep was close to the suggested threshold.
This morning’s assessment of a second kudzu bug insecticide screening test near LaGrange in Lenoir County yielded similar results, with all insecticides providing more than 98% control except for Orthene and Belay at the 3-day check (Azera was not included in this test). A more comprehensive data base of kudzu bug insecticide efficacy comparisons can be found on our blog.
Producers are strongly encouraged to sweep field interiors. Many soybean fields will be below nymph threshold and can quickly be ruled out, while others may contain high enough levels of nymphs and to justify treatment.
Finally, podworms are still a potential threat to later planted beans that are still blooming and stinks bugs can still pose a threat at any time during pod fill. At a minimum, higher risk soybean fields should be assessed regularly until pod fill.