260 Invasive Stink Bugs and Related Species (Pentatomoidea)
Because fruit trees or vegetables are generally not available as a food source at this time, they utilize
surrounding uncultivated vegetation as the first food source (Adachi 1998). Halyomorpha halys adults,
after emergence from overwintering sites, generally do not enter wheat fields and vegetable plots but
disperse to woody plants such as white mulberry, elm species, willow, Chinese scholar tree, Japanese
yew, and cedar trees (Yanagi and Hagihara 1980, Qin 1990). The number of adults at this time, in any
particular location, is dependent upon the abundance and proximity of trees and pine cones that serve as
a main food source (Ohira 2003).
When temperatures rise above 20°C in spring, the adults begin to migrate to apple, peach, or pear
orchards. They also can utilize other host plants such as acacia, oriental arborvitae, and elm trees if
orchards are not nearby or tree fruits are not ready for feeding (Qin 1990). Although this bug was
observed in pines, it cannot survive when reared only on pine (Yanagi and Hagihara 1980). This indi-
cates, of course, that pine is a temporal host plant early in the season before the adults move to other host
plants, which generally are fruit trees and vegetables.
4.4.7.3 Nutritional Attributes Associated with Host Plants and Cropping
and Management Practices affecting Halyomorpha halys Movement
4.4.7.3.1 Nutritional Value of Plants
Adults of Halyomorpha halys move into orchards or other crops when the sugar content of fruit increases
(Lee et al. 2009). A high density of adults frequently is observed in apple or pear orchards at this time.
However, the number of eggs laid within the orchards sometimes is lower than on other host plants
around the orchard (Zhang et al. 2007) even though apple and pear can satisfy the nutritional condition
of growth and development of this bug. When fruits or vegetables are not available or begin to senesce,
H. halys disperses to utilize other plants nearby such as haw, pomegranate, elm, white mulberry, paulow-
nia, and groundnuts (Yanagi and Hagihara 1980, Zhang et al. 2007).
Other chemical compounds in plants such as tannin can affect movement of Halyomorpha halys
adults. In persimmon, concentration of soluble tannin decreases as fruits mature. In June and July, when
persimmon is not mature, the concentration of tannin is high and the fruit is not suitable food for the bugs
(Lee et al. 2009). However, in autumn, when the tannin content drops, H. halys moves to persimmon and
begins to damage fruits.
4.4.7.3.2 Intercropping
The complicated environment in and around the orchard can be a key factor for movement and dispersal
of Halyomorpha halys among commodities. For example, in Korea, sometimes beans or pepper are inter-
planted in persimmon orchards, and such intercropping provides an excellent opportunity for H. halys
to fully utilize both bean and persimmon for their survival and reproduction with minimum movement.
4.4.7.3.3 Chemical Control
Because Halyomorpha halys frequently moves to utilize a variety of surrounding vegetation, Zhang et al.
(2007) suggested a control strategy utilizing spraying of surrounding forest habitats using insecticides, use
of attract and kill systems, bagging of fruit, and the use of natural enemies to reduce H. halys populations.
However, Watanabe et al. (1994) discussed a similar strategy using insecticide applications to surrounding
environments, stating that this might be difficult to utilize because of concerns about the impact on forest
ecosystem that H. halys inhabits. In addition, although H. halys is susceptible to various insecticides, the
adults have strong flying capability so they easily can escape and seek other hosts when pesticides are applied.
4.4.7.4 Movement from Crops and Surrounding Vegetation to Overwintering Sites
When available food sources become scarce and temperatures decrease in autumn, adults of Halyomorpha
halys move to overwintering sites. Sometimes, a large number of adults aggregate and then move to over-
wintering sites along mountain foothills (Yanagi and Hagihara 1980). The choice of overwintering sites
by H. halys in open areas is related to humidity and temperature conditions (Wang and Wang 1988).