616 Invasive Stink Bugs and Related Species (Pentatomoidea)
did not always equate to deeper penetration (Esquivel 2015), and the length of the second segment
appeared to influence this observation (JFE, unpublished data). All penetration estimates are conserva-
tive because the model does not account for bodily behaviors when feeding, but the model should be
applicable to all heteropterans feeding in a similar manner and may be used to determine both potential
feeding damage and delivery of stylet-borne pathogens.
13.1.4 Overview of Pathogens Transmitted by Pentatomoidea
No heteropterans are known to transmit spiroplasmas or fastidious xylem-colonizing bacteria. The for-
mer are transmitted exclusively by leafhoppers (Mitchell 2004) and all known insect vectors of the
latter are sharpshooters (Cicadellidae) or spittlebugs (Machaerotidae) (i.e., dedicated xylem-ingesting
Auchenorrhyncha [Eden-Green et al. 1992, Purcell and Hopkins 1996]). No pentatomid species are yet
known to transmit fastidious phloem-colonizing bacteria, although a coreid of comparable size, Anasa
tristis De Geer, transmits cucurbit yellow-vine disease (Bruton et al. 2003). Pentatomoids are most
strongly associated with the transmission of fungal diseases but also have been implicated in the trans-
mission of a virus, a phytoplasma, non-fastidious bacteria, and trypanosomatid plant parasites (Mitchell
2004). The close association with fungi primarily revolves around the intimate relationship between
Heteroptera and Eremothecium coryli, which causes disease on a wide variety of crops. Of 36 species
of bugs associated with this yeast, 17 are pentatomids (Mitchell 2004). The economic importance of
pentatomids as vectors is illustrated clearly by species in the genus Lincus Stål, many of which transmit
potentially devastating trypanosomatid diseases of oil palm and coconut (Camargo and Wallace 1994).
13.1.5 Selective Transmission — Role of Pathogen Localization
Nezara viridula has been shown to have the capacity to transmit a strain of an opportunistic bacterium
Pantoea agglomerans (Ewing and Fife) marked with antibiotic resistance into cotton bolls resulting in
disease (Medrano et al. 2007). In that study, insects were provided a food source contaminated with
the bacterial pathogen and then caged with cotton bolls for 2 days. To determine whether the insects
acquired the marked pathogen, the bugs were surface sterilized and pulverized, and suspensions of the
whole insect homogenate were selectively cultured on bacterial media with the antibiotic. Bolls were har-
vested 2 weeks following the caging period with the insects. Minimal seed and lint damage along with
an absence of disease was observed in bolls caged with insects not harboring the marked P. agglomerans
strain. Conversely, bolls fed upon by insects that carried the cotton pathogen had infection symptoms
comparable to those observed from field-grown diseased bolls. Further, P. agglomerans with antibiotic
resistance was recovered from diseased seed and lint tissue; thus, transmission by N. viridula was estab-
lished. Using the same vector model, Medrano et al. (2009a) tested the potential of N. viridula to both
acquire and transmit other opportunistic cotton pathogens including two bacterial pathogens [P. anana-
tis (Serrano) and Klebsiella pneumoniae (Schroeter)] and the fungus Eremothecium coryli. Both bacteria
were marked with antibiotic resistance; the fungus is not part of the insect’s normal microbial flora.
Interestingly, all three microbes were detected in insects that were provided a food source contaminated
with one of the three pathogens; however, only the fungus was transmitted into cotton bolls.
The selective transmission of both Pantoea agglomerans and Eremothecium coryli (but not P. anana-
tis or Klebsiella pneumoniae) was then studied by surgically removing and analyzing components of
the insect including the rostrum, head (i.e., salivary glands), and the alimentary canal (Esquivel and
Medrano 2012). Although all of the microbes were detected in the alimentary canal, only those transmit-
ted by Nezara viridula into cotton (i.e., P. agglomerans and E. coryli) were also found in the rostrum and
head. Therefore, the vector potential of the insect is based not only on whether it is harboring a pathogen
but where the microbe is residing within the insect. All three of the bacteria used in this work are bacilli
(i.e., rod-shaped). However, both P. agglomerans and P. ananatis are flagellated, which is important
in both movement and adhesion (Bergey et al. 1974). Conversely, K. pneumoniae is not motile (i.e., no
flagella), yet the cells exude a thick, sticky exopolysaccharide (mucus). Eremothecium coryli consists of
multiple cellular forms including budding yeast, spores, and mycelia (Koopmans 1977). The genomes of
both opportunistic strains of P. agglomerans (Medrano and Bell 2012) and P. ananatis (Medrano and