Brown marmorated stink bug (BMSB) and samurai wasp: (2023 version)
Captures of BMSB in pheromone traps in 2022 varied among locations in Virginia, but appeared to show a general decline, relative to previous years. The samurai wasp, Trissolcus japonicus, was again monitored in Frederick County, VA and at 7 other locations across Clarke, Loudoun, Fauquier, Shenandoah, and Rockingham counties in Virginia. It was also monitored for the fifth season at the nine sites between northern and southwest Virginia where it was released in 2018 and 2020. In Frederick county, samurai wasps again showed evidence of being widely distributed and abundant. Monitoring at the four counties where it had not been released yielded samurai wasp detections at all sites, suggesting that it has spread naturally from Frederick county. Across the nine release sites in Virginia, samurai wasp was detected for the first time at two new sites in Rappahannock and Nelson counties and in Hillsville, in Carroll county. The project that sought to promote the establishment of samurai wasp was completed in 2022, and ultimately resulted in its detection at 8 of 9 release sites. Although the number of detections was generally low, we can conclude that it is now established throughout much of the tree fruit production area in Virginia, although more time will be needed for populations to increase and impact BMSB noticeably. A long-standing recommendation of tree fruit Extension Specialists is to avoid or minimize the use pyrethroids during post-bloom, due to their disruptive effects on natural enemies of secondary pests. Consequently, we have not included them or pre-mixes containing them in most post-bloom cover sprays for pome fruit. However, the most effective products for BMSB continue to include Belay (neonicotinoid), some of the pyrethroids (Brigade, Perm-UP, Pounce, Baythroid, Danitol, Warrior II), Lannate (carbamate), and pre-mixes that contain a pyrethroid (Endigo ZCX and Leverage 360). Brigade was recently labelled for use in all pome and stone fruit against BMSB, but Bifenture continues to be labelled only for use in pears (see writeup on page 38). Because the residual effectiveness of products for BMSB control varies considerably and may not extend beyond several days, particularly following rain, we continue to recommend alternate-row-middle applications at about 7-day intervals for managing BMSB injury when its populations require. Peaches and nectarines are vulnerable to injury from BMSB from fruit set onward, while injury to apples can be detected from about mid-June onward. For additional information about BMSB and its management in tree fruit orchards, see www.stopbmsb.org.