Researchers from around our region are reporting much higher captures of brown marmorated stink bug (BMSB) in pheromone traps than have been recorded at this point in the season in recent years. Based on experience, we might expect BMSB numbers to increase over the next few weeks. Its feeding on tree fruits in August and September can result in substantial injury at harvest. Also, of course more adults can translate to higher numbers of BMSB invading homes and other buildings during their dispersal to overwintering sites between the latter portion of September through much of October. My post on August 11 included a table of insecticides that are considered effective against BMSB and a a reminder that scouting for BMSB injury (photos below) in apple orchards at this point might be most efficiently accomplished by examining fruit from the mid- and upper canopy of trees in border rows adjacent to woods; this is the “zone” where its injury at harvest has been most prevalent. I encourage growers to be vigilant in paying attention to this as the crop matures.
Brown marmorated stink bug (BMSB) pheromone traps are showing the presence of new adults and late instar nymphs that will soon molt to the adult stage. Captures vary among sites, but at some locations are considerable for this point in the season. These adults will produce another generation of nymphs that will become the adults that invade buildings in the fall when they seek overwintering sites. Nymphs are considered more susceptible to insecticides than adults, but older nymphs (3rd and 4th instars) can cause similar injury to fruit as adults. BMSB populations (based on captures in traps) are almost always highest between late August and early October, and feeding by BMSB during this period can cause considerable fruit injury and in some cases, injury to apples that is not apparent at harvest but is expressed after a period in post-harvest cold storage. Woodlands next orchards tend to be the “riskiest” borders in terms of BMSB prevalence, and injury to apples tends to be highest in fruit at the top and middle of trees in border rows next to woods. To gain a sense of BMSB injury at this point in the season, scouting could reasonably focus on fruit from these trees and canopy locations.
BMSB management options from this point forward are summarized in the table below. Because the residual efficacy of most insecticides against BMSB is fairly short, alternate-row-middle sprays against it at 7- to 10-day intervals are considered strongest. Note that many of the products listed below are pyrethroids or contain a pyrethroid; they and Lannate can cause secondary pests to flare.
With respect to codling moth (CM) and oriental fruit moth (OFM), management of third generation CM and fourth generation OFM occurs in August. The degree-day egg hatch models are not used to guide management for the final generation of these pests. Rather, pheromone trap-based thresholds can inform decisions about whether control is needed. Average captures (e.g. across 2 or more traps) per week of more than 5 CM per trap and more than 10 OFM per trap are considered to reflect a population that should be managed.