Bagrada hilaris (Burmeister) 225
B. hilaris typically does not colonize crops until mid-June to mid-July (Tessa R. Grasswitz, personal
observation), allowing early-spring plantings of quickly maturing crops, such as Asian or mustard
greens, arugula, and radishes, to be sown and harvested (either outdoors or under protection) prior to
the first appearance of adults of this bug. The same appears to be true in parts of California (Lambert
and Dudley 2014) and Arizona (Huang et al. 2013). However, in some areas (e.g., southern New Mexico),
B. hilaris may be active all year (Taylor et al. 2015), precluding such an approach.
3.6.2.2 Trap Cropping
Throughout its range, Bagrada hilaris shows a distinct preference for brassicaceous crops, although
there are widespread reports of its occurrence on other plants (Reed et al. 2013a; Reed et al. 2014; Deep
et al. 2014a, b; Huang et al. 2014b) (see Section 3.4.2, Host Plants). Within the Brassicaceae, the bug
shows distinct preferences for different species and varieties (Huang et al. 2014b), and these preferences
may form the basis of trap-cropping systems.
Trap cropping (or diversionary cropping) for Bagrada hilaris first was reported over a century ago in
South Africa by Howard (1906), who suggested planting mustard crops in or around cabbage and cauli-
flower fields to divert the insect away from the latter crops. Similarly, trap crops of Indian mustard planted
prior to cabbage and followed by insecticide sprays have been used successfully to prevent damage from
a number of key cabbage pests including B. hilaris (Srinivasan and Moorthy 1992, Reddy 2013). In a
recent study, a radish cultivar was shown to be more attractive to B. hilaris adults than other brassica crops
(Huang et al. 2014b). Similarly, Makwali et al. (2002) found that wild radish, Raphanus raphanistrum L.,
was highly attractive to B. hilaris and suggested it could be used as a diversionary host to protect bras-
sica crops. Aalbersberg et al. (1989) found that Japanese radish planted as a border crop around wheat to
enhance aphid control unintentionally attracted high numbers of B. hilaris that eventually damaged the
wheat. In New Mexico, a field-scale experiment involving more than 20 different host plants showed that
spring raab, Brassica ruvo L. H. Bailey, was highly preferred (Tessa R. Grasswitz, unpublished data).
Spring raab, therefore, has potential as a trap crop by sowing early to concentrate and control populations
of this bug prior to establishing other brassicaceous cash crops. However, this approach is feasible only if
an effective control method is available for use on the trap crop. Flame weeders or vacuum devices may
be suitable options when the trap crop is relatively small. Both techniques become less effective as the
trap crop grows and increases in size. Sweet alyssum, Lobularia maritima, an ornamental annual brassica
widely grown as an ‘insectary’ plant to attract beneficial insects (Brennan 2013), also has been suggested
as a perimeter trap crop to protect edible brassicas, using vacuuming as the control tactic (Sooby 2014).
The low-growing, compact nature of this plant would make it amenable to vacuuming even when fully
mature. However, there is evidence that it is not a highly preferred host (Huang et al. 2014b), which would
reduce its utility as a trap crop if more favored hosts were present in the vicinity.
3.6.2.3 Sanitation (Clean Culture)
In Africa, the importance of clean culture and sanitation long has been recognized as essential for
avoiding Bagrada hilaris outbreaks on brassicaceous crops (Lounsbury 1898, Howard 1906). Therefore,
control of weedy hosts in and around the planting area and post-harvest destruction of crop residues com-
monly are recommended as methods of preventing or slowing Bagrada population build-up (Sachan and
Purwar 2007, Hill 2008, Nyabuga 2008, Abrol 2009, Anonymous 2012, Banuelos et al. 2013, Reed et al.
2014). In addition, because B. hilaris usually deposits its eggs in the soil (Taylor et al. 2014), it has been
suggested that frequent cultivation of leafy vegetable beds during the season may help reduce B. hilaris
populations (Bok et al. 2006, Nyabuga 2008).
3.6.2.4 Crop Isolation
In situations where multiple brassicaceous crops are grown concurrently (e.g., small-scale organic farms),
spatial separation of crops is recommended for management of Bagrada hilaris because close proximity
to a highly preferred host increases the chances of less favored crops becoming infested. Primarily, this