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Mozena obtusa
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Summary
Mozena obtusa is native to North America where it can
be abundant and damaging. Host specificity testing suggested
that the Australia genus Neptunia, which is closely
related to Prosopis, may be at risk so no application
was made to release this insect in Australia. Furthermore,
results suggested an interesting interaction between rhizobia,
nitrogen sources, plant quality and host-specificity. This
interaction would certainly need to be resolved before we
could confidently predict host specificity under field conditions.
Taxonomy and origin
Mexico; USA states of Arizona, Kansas, New Mexico, Oklahoma,
and Texas (Ward et al., 1977).
Lifecycle
Nymphs and adults pierce immature pods and suck out the plant
juices (Ueckert 1973). It also attacks tender young leaves
and flowers (Ward et al. 1977). They appear in the
field as soon as fruit buds begin to break and can remain
active until August in Texas (Swenson 1969, cited by Kingsolver
et al. 1977).
First instars are generally sedentary and non-feeding. The
next four nymphal instars and adults typically feed on young
and immature foliage. They probably overwinter in the native-range
as adults, probably in reproductive diapause.
Leaf-footed bugs reduce plant fitness by reducing the percentage
of viable seeds in attacked pods (Ueckert 1973). Reduction
in viable seed production may reduce spread of the plant.
Attack on young pods causes them to abort prematurely (Swenson
1969, cited by Kingsolver et al. 1977). Attack on young
leaves and flowers reduces plant vigour and seed production
respectively.
Host-specificity
Host-specificity testing showed that complete development
was possible on all mesquite species present in Australia
and on at least three Neptunia species. However, the
onset of reproductive diapause prevented a comparison of subsequent
oviposition on mesquite and non-targets. Circumstantial evidence
does, however, suggest that oviposition is determined by pre-alighting
responses.
Results from laboratory trials were typically highly variable
suggesting that plant quality might play an important role
in early nymphal survival. Available evidence suggests that
the composition of nitrogen compounds in plant sap might be
critical. Nitrogen composition is likely to be influenced
by the relative contributions from each nitrogen source, and
the presence of rhizobia. The relationship between rhizobia,
nitrogen sources, plant quality and host-specificity needs
to be resolved before accurate predictions of potential non-target
impacts in the field can be made.
Mass-rearing and release
Host-specificity testing not completed, but may not be sufficiently
host-specific. An application to release was not submitted.
Current research
None. Any future research would aim at elucidating the relationship
between environment, plant nitrogen, plant quality and host-specificity.
References
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van Klinken, R.D. (1999). Developmental host-specificity
of Mozena obtusa (Heteroptera: Coreidae), a potential
biocontrol agent for mesquite (Prosopis species).
Biological Control 16, 283-290.
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