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This is Jack Bacheler, Extension Entomologist at North Carolina State University with the weekly insect update. Today is Thursday August 2.
Like our rainfall patterns, insect levels appeared to be all over the map this past week, with each consultant or grower sharing a different story. With light trap catches still surprisingly low in most areas, cotton bollworm establishment on squares and under bloom tags seems to be far less of a present issue than possible green and brown stink bug damage to young bolls. A high proportion of out cotton is still in the most susceptible 3rd through 5th week of bloom stage when the protective 10% internal quarter-sized boll threshold is recommended. We are still getting reports of boll damage ranging from single digits to the mid to high 20’s across different areas of the state. This is the prime time to be vigilant. Remember that by confining boll damage assessments to approximately inch bolls, counting the same old boll damage from one week to the next is eliminated, thus minimizing sprays in situations where stink bugs may no longer be present. We think that soybeans may also be subjected to higher than average levels of stink bugs in 2012, especially when pod development has begun, a stage at which stink bugs become increasingly attracted to bean fields.
The corn earworm (bollworm and podworm) moth mid-July to mid-August flight peak seems to have passed in southern NC, with our highest reporting light trap at Johns in Scotland County reaching 436 moths on Monday July 23 followed by a Wednesday count of 189 and a Friday count of 173. This past Wednesday’s August 1st count of only 35 moths suggests that the major flight may be on the decline in that area. However, at least some level of bollworm eggs have been reported throughout the state this week, so, if not already underway, scouting for 2nd stage bollworms is recommended all the way to the Virginia border.
Oddly, at a number of locations in North Carolina in 2010 and in 2011, the next typically small August to early September corn earworm moth generation was larger than our so-called “major” earlier flight. Although Bollgard II and WideStrike cotton varieties normally escape a high proportion of the possible bollworm damage from this late August to early September flight, the story can be different for soybeans when late flights and subsequent podworm development coincides with susceptible June planted beans, especially with maturity groups that are in late bloom to early pod fill.
In a test in Scotland County, kudzu bug nymph levels were close to the 15 nymphs per 15 sweep threshold in the untreated plots for several maturity groups in the April and May plantings this past Monday. Levels in the beans planted behind wheat were far lower. A scattering of fields has already been treated across a wide area ranging from the far western Piedmont to Hyde County. In central Georgia in 2011, kudzu bug nymph levels in untreated plots in two tests didn’t peak until late August, and were the range of 200 to 300 nymphs per 20 sweeps. The good news was that yields were preserved by a single well-timed spray at the recommended threshold in late July.
We’ll provide our next update this coming Wednesday on August 8. See you then.