226 Invasive Stink Bugs and Related Species (Pentatomoidea)
is due to the tendency of adults and nymphs to disperse short distances by walking (Tessa R. Grasswitz,
personal observation). Similarly, in the southwestern United States, larger-scale commercial growers are
encouraged to avoid planting brassicaceous plants near crops considered to be alternative hosts for the
bug (e.g., cotton, Sudan grass, and corn) (Palumbo 2014).
3.6.2.5 Mechanical Control and Exclusion Techniques
Historically, in Africa, gardeners and small-scale farmers resorted to mechanical control methods such
as shaking infested plants and dislodging the insects into pans containing paraffin (Lounsbury 1898)
or removing Bagrada hilaris either by hand or with sweep nets (Howard 1906, Nyabuga 2008). Early
attempts to protect cabbage crops from injury by covering them with butter muslin or with frames cov-
ered with mosquito netting were unsuccessful (Howard 1906). More recently, in the United States, a
combination of low metal hoops and floating row covers has been found to be effective for excluding
B. hilaris provided that a good seal is maintained between the edge of the fabric and the soil and no holes
are present in the cover (Reed et al. 2014, Tessa R. Grasswitz, personal observations). This approach
has proven useful in establishing autumn-sown brassicaceous plantings in central New Mexico with the
additional benefit of providing some degree of frost protection to the plants during the winter. Such an
approach is useful for small-scale producers, but may not be practical on a larger scale because of the
expense and labor requirements (Frederic J. Klicka, personal communication).
3.6.2.6 Organic Insecticides
Field tests of insecticides currently approved for use on brassicaceous plants in organic production sys-
tems have generated inconsistent results, indicating they generally are not very effective (Palumbo and
Natwick 2010, Palumbo et al. 2013a, Grasswitz 2014) (see Section 3.6.1.4, Chemical Control). The vari-
ability of these results may be related to environmental conditions and the relatively rapid breakdown
of most organic insecticides under intense UV radiation and/or high temperatures. For example, a 1.4%
commercial formulation of pyrethrin gave much better results against Bagrada hilaris in New Mexico
when applied in October, when temperatures were cooler, than in August (Grasswitz 2014). In India, labo-
ratory bioassays with a neem-based product resulted in 96% mortality of a mixed population of adults and
nymphs 2 days after treatment (Ghosal et al. 2006). However, in greenhouse tests in the United States, a
70% formulation of neem oil proved ineffective against both nymphs and adults (Grasswitz 2013a).
Laboratory testing of products based on various entomopathogenic fungi (Dara 2013) indicates they may
have potential in situations where temperatures are sufficiently low and humidity high enough to support
the development of epizootics. For example, in some climates, such materials might be appropriate for use
as soil drenches or surface applications because most eggs of this bug are laid just below the soil surface
(Taylor et al. 2014), and first and second instars frequently are observed aggregated on the soil surface
rather than on the plant (Tessa R. Grasswitz, personal observation). If irrigation water is readily available,
such applications might be potentiated by use of overhead sprinklers, although this has not yet been tested.
In general, published data on the efficacy of organically approved insecticides in the United States
are too scarce and variable to support specific recommendations at this time. In certain geographic
areas, some organic insecticides require an organically acceptable buffering agent to reduce the pH.
An organically approved surfactant also is recommended for some brassicaceous crops. These require-
ments impose an additional constraint on growers. Although a few such products are on the market (e.g.,
Constant BupHer™ and Natural Wet® surfactant), they are not readily available in all states and, in some
cases, are not sold in sizes appropriate for smaller-scale producers.
3.6.3 Natural Enemies
3.6.3.1 Parasitoids
The key natural enemies of Bagrada hilaris have been poorly studied in comparison to other widespread
pest pentatomids. In South Africa, Howard (1906) stated “No natural enemies of the bug have been