A couple of new things to report from our statewide soybean survey: soybean aphid has greatly exceeded the threshold (250 aphids/plant) in at least two fields in Gloucester County. Our scout has been watching this area closely for several weeks as it has been the ‘hot spot’ in the state. As of this week, the population has jumped. As the beans are still in the R4-R5 growth stage, we are recommending a pyrethroid treatment. Pyrethroids are effective in controlling this aphid species.

The scout also brought in samples of brown marmorated stink bug (BMSB) nymphs collected from soybean fields in three counties, Culpeper, Augusta and Clark. These are in the upper- central and northern Virginia. The counts were low in these fields, only about 1/15 sweeps, which is not alarming, but definitely warrants watching. Reports of huge masses of BMSB are starting to come in from places like Fairfax, VA with bugs massing on trees, especially maples, and vegetables of all kinds.

Earworm moths are still flying. Trap catches are high in many areas, and windshields are spattered. One fellow commented that the other night coming home from a meeting, he had to stop twice to clean the moth gunk off his windshield. One observation, and I hope this holds, is that in the past this late season moth flight did not result in new worm infestations. A lot of insect behavior is relegated by environmental cues. Days are definitely getting shorter. Is this reduced photoperiod (shorter day length) causing moths not to lay as many eggs? Not sure, but for whatever reason, in my experience it has been rare to see worm infestations initiate in September. We are hearing of many fields with a few earworms, maybe left over from the earlier flight, but none with the huge numbers we had a few weeks ago. Let’s hope we are finally seeing the end of this pest, for this season at least.

Soybean loopers are now being reported in soybean fields across much of the eastern side of the state. In past years they were mostly confined to southeastern counties. This infestation has broken all the records in terms of intensity (as many as 100+/15 sweeps in some fields) and geography (now being reported from Middle Peninsula and Northern Neck counties). This must be due to the persistent hot, dry weather, and the high percentage of fields previously treated with insecticides.

Loopers are easy to identify but there is some confusion about their color. Soybean loopers have both a ‘green’ and a ‘black’ color phase (see the attached image). We are seeing both color phases in our samples. There may be some cabbage loopers (a completely different species) mixed in, but we have not verified this. There are no exact thresholds for loopers in soybean so treatment should be based on the amount of leaf feeding in relation to the size of the total canopy. But, a very loose rule of thumb could be that 20 or more per 15 sweep net sweeps may constitute a threat. Fewer than that, especially in tall, full canopy fields probably does not constitute a threat. Some fields are getting close to maturity with pods and leaves beginning to yellow. Loopers are not a threat to those fields. Pyrethroids should not be figured into a looper treatment decision. They are less than effective. If stink bugs are present in looper infested fields, I would consider adding Orthene to the looper insecticide. Orthene will provide good control of both green and brown stink bugs where the pyrethroid would miss some of the browns. Oddly, we are seeing more brown stink bugs in some fields than greens, which is opposite of what we are used to seeing.

We have initiated 5 different field trials to evaluate the effectiveness of many different insecticides/rates for loopers. Results will be presented at our annual Pre-Harvest Field Tour scheduled for Sept. 14.
Additional information: soybean-looper-color-phases-herbert-2010-ppt