250 Invasive Stink Bugs and Related Species (Pentatomoidea)
this time, and individual bugs are difficult to find. Mating and oviposition by the “spring adults” begin
in mid-late May and may continue throughout a female’s lifespan, which European studies indicate can
last past August (Haye et al. 2014b). In temperate regions, females enter and leave overwintering repro-
ductively immature and unmated (Anne L. Nielsen, unpublished data). After eclosion and presumably
diapause termination, females require an additional 68 DD12.7 – 148 DD 25 (DD12.7 – degree days above
12.7°C; DD 25 – degree days above 25°C (Yanagi and Hagihara 1980, Nielsen et al. 2008a) to become
reproductively mature. At 30°C, this takes 32–35 days. Adults mate and eggs are oviposited in clusters
on the undersides of leaves in groups of 28 (Kawada and Kimura 1983b). Parthenogenisis has also been
reported in H. halys (Fengjie et al. 1997). The temperature range of the egg incubation period, To and
Tm (To – minimum temperature threshold, Tm – maximum temperature threshold) is similar to those for
nymphs and adults at 13.94 and 37.73°C, respectively (Nielsen et al. 2008a). During oviposition, females
transfer gut symbionts to the egg chorion surface. After hatching, first instars aggregate on the choria,
presumably feeding on the symbionts. Disruption of this behavior significantly reduces survivorship
(Nielsen et al. 2008a). Further, surface sterilization of the chorion to remove symbionts results in signifi-
cant reduction in survival (Taylor et al. 2014). H. halys requires 538 DD 14 to develop from the egg through
the five instars to adult eclosion. The minimum (To) and maximum (Tm) temperature thresholds are
14.14 and 35.76°C, respectively. These thresholds are similar to those determined by Baek et al. (2017)
using a nonlinear Briére model. Temperature also has been shown to impact H. halys regional patterns.
Venugopal et al. (2016) found using multivariate analysis that average June temperatures and distance
from source population negatively impacted H. halys populations. They also showed that H. halys was
not present in fields when average June temperatures were above 23.5°C. When they were present, high
population levels were related positively with the percent-developed open area and percent forest cover
at a 250 m scale.
Halyomorpha halys is a highly mobile, polyphagous species. The exact number of reported host plants
varies between authors, but over 175 have been identified throughout the United States in a collaborative
factsheet by researchers (Anonymous 2015b; see Table 4.1).
Classification of host plants for polyphagous insects first requires a definition of ‘host plant’. Here we
define a host plant as a species where multiple life stages occur in multiple years (Nielsen and Hamilton
2009b). Surveys conducted at a semi-landscaped horticultural garden containing plantings of both native
and non-native plantings identified host plants during the establishment phase of Halyomorpha halys
in Allentown, Pennsylvania. All stages of H. halys including first instars were found on Paulownia
tomentosa (Thunb.) Steud. (2005-2007), Fraxinus americana (2005–2007), Liquidambar spp. (2006),
Viburnum opulus var americanum (2007), V. prunifolium (2007), Pyrus sp. (2006), and Pyrus pyrifolia
(2006–2007). The identification of early-season host plants by Nielsen and Hamilton (2009b) through
visual and beat surveys on ornamental hosts did not identify significant trends for adult populations.
Nymphs however were significantly greater on P. tomentosa (Nielsen and Hamilton 2009b). Martinson
et al. (2016) also examined naïve plants based on their geographis origin (Asian versus non-Asian) in
commercial nurseries. These authors found that H. halys was more abundant on non-Asian plants when
compared to Asian varieties. Late instar nymphs were observed on host plants where egg masses or young
instars had not been observed previously. At the time, it was hypothesized that the nymphs changed host
plants depending on nutritional needs and changing host plant phenology. For nymphs, although the first
instars tend to remain aggregated around the egg mass, later instars show a strong capacity to disperse
in the laboratory and field. In the laboratory, the later instars were capable of climbing 6-8 meters (m)
in 15 minutes (Lee et al. 2014b). In the field, the third and fifth instars walked on average 1.3 m and 2.6
m, respectively, over 30 min on a grassy surface. H. halys nymphs will disperse to more attractive host
plants based on plant phenology with a positive relationship observed as ‘fruits’ mature (Brett R. Blaauw,
unpublished data; see Acknowledgments).
The importance of host plant quality for Halyomorpha halys nymphal and adult development has been
of considerable interest to researchers. Funayama (2004) showed that females laid significantly fewer
eggs when reared on apple than on a high protein diet of peanut and soybean, suggesting that apple did
not meet the nutritional requirements. Funayama did not report on the survivability of these offspring
on apples. However, laboratory trials by other investigators suggest that apple fruits do not support
nymphal development (Acebes-Doria et al. 2016a). Of the other host plants evaluated, H. halys nymphs