222 Invasive Stink Bugs and Related Species (Pentatomoidea)
susceptible to feeding injury by Bagrada hilaris up to the sixth leaf node stage. However, beyond this
point, plants are capable of withstanding feeding injury without any significant loss in head production
(John C. Palumbo, unpublished data).
3.6 Management
3.6.1 Conventional Cropping Systems
3.6.1.1 Sampling/Monitoring
Reliable sampling plans or monitoring tools for Bagrada hilaris in commercial cole crops have not
been developed as yet. However, field observations suggest that sampling for the presence of B. hilaris
in seedling cole crops should be conducted from mid-morning to late afternoon when ambient tem-
peratures are warm and adults are most abundant on plants (Huang et al. 2013). University of Arizona
Cooperative Extension recommendations suggest monitoring begin immediately upon seedling emer-
gence or transplanting (Palumbo 2014). Recent research has shown a strong association between the
proportion of plants with fresh feeding injury and population density of B. hilaris, indicating that
fresh feeding damage will provide an accurate measure of B. hilaris abundance in commercial fields
(Palumbo and Carrière 2015). Consequently, growers and consultants are encouraged to sample plants
for fresh feeding signs on cotyledons and young leaves when monitoring for the presence of B. hilaris
( Pa lu mbo 2014).
Chemical attractants that might be used as lures in monitoring traps, such as those described by
Joseph (2014), also are under investigation. For example, chemical analyses indicate that adults of both
sexes of Bagrada hilaris release qualitatively similar volatile blends (consisting of nonanal, decanal, and
(E)-2-octenyl acetate), but that males produce ≈2.8 times as much of (E)-2-octenyl acetate as do females
(Guarino et al. 2008). Furthermore, in olfactometer tests, females responded positively to the odors both
of live males and hexane extracts of males, but not to the odor of other females. This suggests that the
elevated levels of (E)-2-octenyl acetate produced by males are involved in long-distance attraction of
adult females to males (Guarino et al. 2008); this finding may have value in developing a pheromone-
based monitoring tool. Similarly, volatile compounds derived from brassicaceous plants also are being
examined for use as attractants in trapping B. hilaris. However, no consistently effective plant-derived
attractants have been identified (Jocelyn G. Millar, personal communication).
3.6.1.2 Cultural Control
Cultural control tactics are discussed more fully in Section 3.6.2 (Organic Cropping Systems). However,
many of these tactics (e.g., trap cropping and alterations in planting date) are equally relevant to develop-
ing integrated management strategies in conventional cropping systems.
Other modifications in farming practices help prevent populations of Bagrada hilaris from reaching
damaging levels, particularly on oilseed mustards. For example, it has been shown that nitrogen fertiliza-
tion should be used conservatively, as high rates on mustards could lead to increased B. hilaris popula-
tion development (Parsana et al. 2001). This recommendation was supported by Sachan and Purwar
(2007) who reported that infestations of the bug were shown to increase as levels of nitrogen applied to
mustard plants was increased. It also has been shown that timely irrigation can reduce pest damage on
seedling crops (Sanchan and Purwar 2007, Singh et al. 2007, Banuelos et al. 2013). On mature crops,
rapid threshing of harvested material has been suggested as a means for minimizing B. hilaris damage
(Abrol 2009). Similarly, planting oil seed brassica crops earlier or later in the season than normal may
allow emerging crops to escape damage from the pest, but results have varied among growing regions
(Lal and Singh 1993, Parsana et al. 2001, Ahuja et al. 2008). In the southwestern United States, grow-
ers increasingly are trying to establish brassica crops (such as broccoli) from transplants rather than
direct-seeding to avoid excessive mortality to emerging seedlings due to B. hilaris feeding (Palumbo and
Natwick 2010, Reed et al. 2013b, Huang et al. 2014a).