256 Invasive Stink Bugs and Related Species (Pentatomoidea)
Across all plant species, there appears to be a strong edge-effect at the field level on the amount of
damage by Halyomorpha halys. In orchard crops, this has been observed in peaches and apples where
H. halys adults are concentrated in border rows on the outer margins of orchards, coinciding with higher
damage (Joseph et al. 2014, Blaauw et al. 2016). In peaches, this edge-effect has been exploited for
management purposes (Blaauw et al. 2014). A geospatial analysis of field corn and soybeans found that
H. halys was the predominant pentatomid species in these crops, and both populations and damage
demonstrated strong edge effects; fields with adjacent wooded habitats had significantly higher stink bug
densities than fields without adjacent wooded habitats (Venugopal et al. 2014). In addition, the plant spe-
cies composition in nonmanaged woodland borders adjacent to soybean fields has been shown to impact
abundance patterns in those fields with clear buildups of H. halys populations in borders dominated by
tree of heaven in July followed by steady movement into field edges (Aigner et al. 2017).
Halyomorpha halys’ polyphagous behavior may be aided by its strong capacity to disperse at land-
scape levels throughout most periods of its lifetime. In laboratory studies where H. halys adults were
tethered to a flight mill, wild populations could be divided into two categories – short distance (≤5 kilometers
[km]) fliers and long distance fliers (>5 km). Short distance fliers comprised 85% of the population and
flew an average of 2 km in 24 hours. Long-distance fliers travelled an average of 66.54 and 75.12 km for
males and females, respectively (Wiman et al. 2014). Where free flight of H. halys was directly observed
and tracked in field studies, the mean flight speed was 3 meters/second along a straight line from take-off
to landing (Lee et al. 2013b).
Adult flight activity occurs primarily at night (Wiman et al. 2014) as adults search for mates or alternate
food resources. Because of this, blacklight traps are a useful monitoring tool for landscape-level movement
of H. halys. This method has demonstrated a 75% annual increase in H. halys’ population size in New Jersey
from 2004 to 2011. Although activity changes throughout the year, a large peak in flight activity occurs
at 685 DD14.17 (Nielsen et al. 2013). Analyses of catches in blacklight traps allowed important geographic
parameters to be elucidated that may be important during population spread. Early in the invasion stage,
there is a strong association with urban environments. Railroads and wetlands appear to facilitate popula-
tion spread. And, finally, association with agriculture has a significant relationship with population density
(Wallner et al. 2014). These analyses support the hypothesis that species associated with human environ-
ments are more likely to be successful invaders (Hufbauer et al. 2012). This may have allowed H. halys to
overcome any Allee effects associated with the genetic bottleneck (i.e., small number of initial individuals)
that occurred during the introduction into the eastern United States (Wallner et al. 2014, Xu et al. 2014).
4.4.2 Symbiotic Relationships
The presence of symbiosis in the order Hemiptera is well known in the Auchenorryncha and
Sternorrhyncha and is found in the diets of various pentatomorphans (Buchner 1965). These relation-
ships are necessary and provide missing dietary components such as amino acids and vitamins not pres-
ent in phloem fluids (Baumann and Moran 1997, Moran and Telang 1998, Douglas 2006). Kenyon et al.
(2015) found that the endosymbiont Candidatus Pantoea carbekii, the primary symbiont in the gastric
caeca lumina of Halyomorpha halys, is obtained when newly hatched first instars feed on maternal
extrachorion secretions present on the surfaces of eggs. The nymphs congregate around their egg mass
and apparently feed on the egg choria to obtain this endosymbiont, which is necessary for development
(Bansal et al. 2014, Taylor et al. 2014). This was demonstrated by Taylor et al. (2014), who showed,
through a series of experiments involving surface-sterilized and untreated eggs, that nymphal develop-
ment and survival was negatively affected if this endosymbiont could not be obtained. They also noted
that nymphs that were negatively affected resulted in adults with reduced fecundity. Studies conducted
to determine if antimicrobials could be used to sterilize H. halys eggs to prevent acquisition showed that
doing so significantly reduced egg hatch, nymphal survival and symbiont acquisition (Taylor et al. 2016).
4.4.3 Mate Selection
Prolonged copulation is common among Pentatomidae, ranging from 1 to 165 hours (Kawada and
Kitamura 1983b, Ueno and Ito 1992). This behavior could have evolved as a mate-guarding tactic to