The Erythrina Stem or Twig borer: A new and Potentially Devastating Pest of Coral Trees in California

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The Erythrina Stem or Twig Borer
A New and Potentially Devastating Pest of Coral Trees in California
Donald R. Hodel, James E. Henrich, Kenneth J. Greby,
Gevork Arakelian, Linda M. Ohara, and Surendra K. Dara
The Erythrina stem borer (ESB)
(sometimes known as the Erythrina twig
borer) (Terastia meticulosalis), a potentially
devastating pest of Erythrina spp. (coral
trees), has been sighted numerous times in
southern California in the latter half of 2015
from San Diego to Ventura. Erythrina, a
member of the Fabaceae (formerly
Leguminosae, bean family) encompasses
about 112 species (Bruneau 1996) and
includes some of our most useful, valuable,
well adapted, and spectacular flowering trees,
Figure 1. Erythrina caffra is one of our most handsome, spring-flowering trees. Santa Barbara, CA. (D. R. Hodel).
Figure 2. Another striking landscape tree is
Erythrina coralloides (Huntington Beach, CA. (D.
R. Hodel).
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adorning landscapes along the coast and
adjacent plains and valleys in southern
California (Figs. 1-5). Indeed, a famous
planting of E. caffra adorning the broad
median of San Vicente Boulevard in Santa
Monica and West Los Angeles was designated
an exceptional planting (Fig. 6) (Hodel 1988).
The plethora of sightings suggests a more
recent introduction but the ESB was recorded
as early as 1973 at Fort Piute in the California
desert north of Needles near the southern tip
of Nevada (CMSD 2016).
The ESB is of special concern for us
because so little is known about its
management and it appears to be especially
destructive on coral trees, infesting seeds,
destroying branch tips, and even killing whole
plants. In Florida where it is native, it is a
serious pest of naturally occurring and exotic
coral trees, which are valued for agriculture,
medicine, and landscape ornament (Powell
and Westley 1993). Indeed, the cultivation of
exotic coral trees in Florida is essentially
impossible because of the ESB (Raven 1974);
the only coral tree that can be cultivated
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Figure 3. Erythrina crista-galli is a handsome
landscape tree. The Los Angeles County Arboretum
& Botanic Gardens, Arcadia, CA (D. R. Hodel).
Figure 4. Erythrina humeana is an attractive, late
summer –flowering tree. Santa Barbara, CA. (D. R.
Hodel).
Figure 5. This gorgeous Erythrina lysistemon makes
a statement in the spring. Golden West College,
Huntington Beach, CA. (D. R. Hodel).
Figure 6. This planting of Erythrina caffra in the
median of San Vicente Blvd. was designated an
exceptional planting in 1988. (D. R. Hodel).

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reliably there is the native Erythrina
herbacea, which likely co-evolved with and is
found over most of the range of the ESB. In
California the ESB has been observed so far
on E. × bidwillii, E. chiapasana, E.
coralloides, E. crista-galli, and E. falcata;
other species will likely be added in the
future. Although much remains to be know
about the ESB in California, at least at this
early stage, the ESB seems to prefer species
of coral trees with more slender stems and
slender regrowth of larger-stemmed species.
Fortunately, another serious pest of
coral trees that is sympatric and co-evolved
with the ESB, the Erythrina leaf roller
(Agathodes designalis), has not yet been
detected in California. The Erythrina leaf
roller and the ESB are in closely related
genera that have tended to niche-partition the
coral tree resource to reduce inter-species
competition (Armstrong and McGehee 1980,
Sourakov 2011).
Much remains to be known about the
natural history of the ESB, and the summary
we provide here of its taxonomy,
identification, distribution, and life cycle and
damage it inflicts on coral trees is mostly
from Arakelian (2016), Sourakov (2011,
2012, 2013), Sourakov et al. (2015), and our
observations of infested coral trees here.
Taxonomy
The ESB is one of five species in the
largely tropical moth genus Terastia, which
ranges from the Americas to Africa, Asia, and
the western Pacific (Sourakov et al. 2015).
The ESB is the only species of the genus
native to the Americas. The other four species
are T. africana, T. egialealis (Africa), T.
margaritis (India), and T. subjectalis (Asia
and western Pacific).
Identification
The adult ESB is a small-sized,
brownish moth with mottled forewings and
whitish hindwings with dark margins (Figs.
7-8). Varying in size, adult forewing
wingspans range from 2.5 to 4.6 cm, and the
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Figure 7. The adult Erythrina stem borer is a small-
sized, brownish moth with mottled forewings and
whitish hindwings with dark margins. (A. Sourakov).
Figure 8. With unspread, mottled-brown wings the
adult Erythrina stem borer is easy to miss. Note the
upward-curved and knobby abdomen. The Los
Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).

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mottled body from 1.5 to 2.5 cm long, the
latter with conspicuous knobs toward the
posterior (Fig. 9) (Sourakov et al. 2015). In
Florida the ESB varies greatly in size, which
largely depends on the seasonal generation
and diet. The spring generation, which feeds
mostly on seeds, is larger than the fall and
summer generation that feeds inside of stems.
For example, wingspans of the spring
generation average about 3.7 cm while those
of the summer and fall generations average
about 3cm and 2.5 cm respectively (Sourakov
2011). When at rest, the mottled- or marble-
brown forewings are effective at
camouflaging the ESB but when the wings
are spread the white hind wings are
conspicuous.
Males and females are similar but the
latter has more beige-brown forewing
markings. In live specimens, the knobby
abdomen is held in a curved, upright position,
mimicking a praying mantis head, which is
possibly a deterrent to predators (Fig. 10)
(Sourakov et al. 2015).
Eggs of the ESB, typically laid singly
in the axil of leaves near stem tips (Fig. 11),
are translucent, white, delicate, dome-shaped
with a reticulated surface, and about 0.8 mm
long (Sourakov 2012). Young larvae are
minute, about 0.5 mm long, and probably
burrow directly into the flower, stem, or
sometimes even a leaf petiole and then follow
it to the stem.
Larvae of the ESB are translucent and
brownish white or cream-colored with a black
sclerotized head and a dark sclerotized
prothoracic plate that becomes lighter as the
larva matures (Fig. 12). Mature larvae are
about 4 cm long. Larvae turn pinkish before
pupation (Fig. 13), especially when they
complete their development on seeds. Pupae
are cigar-shaped, light brown, and enclosed in
a loose, double-layered cocoon (Figs. 14-15)
(Sourakov 2011).
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Figure 9. Note the knobby posterior end of the
abdomen of this adult Erythrina stem borer. (A.
Sourakov).
Figure 10. In live specimens, the knobby abdomen
of the Erythrina stem borer is held in a curved,
upright position, mimicking a praying mantis head,
which is likely a deterrent to predators. (A.
Sourakov).

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Distribution
Endemic to the Americas, the ESB
occurs from South Carolina to Florida and
west to Arizona (and now California) in the
United States and south to Argentina.
Although recorded from Hawaii (Swezey
1923, Zimmerman 1958), this report is now
thought to be misidentification. Numerous
publications list it as part of African or Asian
faunas, but that misconception has been
recently clarified (Sourakov et al. 2015), and
it seems to be a strictly New World species,
with superficially similar but genetically
distant relatives in other tropical regions.
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Figure 11. Eggs of the Erythrina stem borer,
typically laid singly in the axil of leaves near stem
tips), are translucent and white. (A. Sourakov).
Figure 12. Larvae of the Erythrina stem borer have
cream-colored bodies and a black head. The Los
Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).
Figure 13. Larvae of the Erythrina stem borer that
feed on seeds typically take on a pinkish hue. The
Los Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).
Figure 14. Pupae of the Erythrina stem borer are
cigar-shaped and light brown. (A. Sourakov).

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Life Cycle and Damage
Larvae of the ESB likely emerge
through the ventral surface of the egg and
tunnel directly into the plant (Sourakov
2012). The downward-boring larvae feed on
stem tissues as they go, hollowing out the
stem (Figs. 16-17) and causing a
characteristic dying-off of stem tips, which
turn black and sometimes collapse (Figs.
18-19). The entire upper and lateral sides of
the plant canopy can be killed. This damage
acts like pruning, forcing out new lateral
shoots below the damaged area; these, in turn,
can become infested and killed. Entire plants
can be killed although this can take up to
several years.
In Florida after killing off stem tips in
the spring, the last instar larvae move into
seed pods, a condition which appears to be
less common in California so far( Figs.
20-21). Feeding on the red seeds typically
causes larvae to accumulate reddish pigments,
changing their color to pink before they
pupate (Fig. 13). In contrast, summer and fall
generations feed inside the stem and do not
feed on the hardened seeds; thus, they are
typically paler in color and do not take on the
pinkish hue. Larvae typically purge the
hollowed out stem of frass by crawling
backwards to the entry hole to defecate (Fig.
22)(Sourakov 2013).
Full grown larvae descend from a silk
thread to the ground and construct their
cocoons in leaf litter to pupate. They have
also been found in cocoons in old dead
flowers at the ends of dead stems or inside
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Figure 15. Pupae of the Erythrina stem borer are
enclosed in a loose, double-layered cocoon, as in
this captive-reared specimen. The Los Angeles
County Arboretum & Botanic Gardens, Arcadia, CA
(D. R. Hodel).
Figure 16. The downward-boring larvae of the
Erythrina stem borer feed internally on stem tissues
near the shoot tips (Erythrina coralloides). The Los
Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).
Figure 17. Larvae of the Erythrina stem borer
hollow out the stem as they feed (Erythrina
coralloides). The Los Angeles County Arboretum &
Botanic Gardens, Arcadia, CA (D. R. Hodel).

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folded up living leaves on the plant (Sourakov
2012).
Adult ESBs are good fliers and can
hover in flight similar to that of the
Sphingidae (sphinx moths) (Sourakov 2012).
This flight ability, along with larval
endophagous feeding habits that provide
some protection from predators, parasites, and
abiotic mortality factors, largely explains why
the ESB has been so successful in infesting
Erythrina plants (Sourakov 2012).
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Figure 18. Dying-off of stem tips, which turn black
and sometimes collapse, is characteristic of the
Erythrina stem borer (Erythrina chiapasana). The
Fullerton Arboretum, California State University,
Fullerton, CA (D. R. Hodel).
Figure 19. Dying-off of stem tips, which turn black
and sometimes collapse, is characteristic of the
Erythrina stem borer (Erythrina × bidwillii). The
Los Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).
Figure 20. Larvae of the Erythrina stem borer can
also attack seed pods (Erythrina crista-galli). The
Los Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).

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Management
Unfortunately, next to nothing is
known about the management of the ESB.
Nearly all attempts at post-infestation
eradication in Florida have failed. Virtually
nothing is known about resident natural
enemies although they must be present; until
they are identified biological control holds
little promise. Perhaps vigilant scouting,
judicious and immediate removal, bagging,
and disposal of infested shoot tips, and
ground and foliar treatment with systemic
pesticides might be effective and justified for
rare, exceptional, and/or noteworthy and
valuable coral tree specimens. Because the
ESB pupates in leaf litter on the ground,
thorough raking and disposal of fallen leaves
might reduce regeneration and provide some
control. Cover/barrier insecticides, like
pyrethroids (permethrin, cyfluthrin,
bifenthrin) or emulsifiable concentrate
formulation of carbaryl, might work well in
killing of newly hatched larvae when they
attempt to bore into the stems; although not
yet tested for ESB, they have relatively long
residual effects and might be effective.
Further work is needed on this pest that poses
a serious threat to California’s ornamental
landscape coral trees.
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Figure 21. Larvae of the Erythrina stem borer can
also attack seed pods (Erythrina crista-galli). The
Los Angeles County Arboretum & Botanic Gardens,
Arcadia, CA (D. R. Hodel).
Figure 22. Larvae of the Erythrina stem borer
typically purge the hollowed out stem of frass by
crawling backwards to the entry hole to defecate
(Erythrina coralloides). The Los Angeles County
Arboretum & Botanic Gardens, Arcadia, CA (D. R.
Hodel).

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Acknowledgements
We thank Andrei Sourakov of the University of Florida for reviewing this paper and
providing some of the images. Readers interested in supporting his important work can contact
Andrei directly (asourakov@flmnh.ufl.edu).
Literature Cited
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Two different patterns of haplotype divergence and a new species of Terastia. Trop.
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_______________
Donald R. Hodel is landscape horticulture advisor for the University of California Cooperative
Extension in Los Angeles. drhodel@ucanr.edu.
James E. Henrich is curator of living collections at the Los Angeles County Arboretum &
Botanic Garden in Arcadia, CA. jim.henrich@arboretum.org.
Kenneth J. Greby is an arborist with ArborPro in Yorba Linda, CA. fastfeat@gmail.com.
Gevork Arakelian is the entomologist with the Los Angeles County Agricultural Commissioner/
Weights & Measures in South Gate, CA. GArakelian@acwm.lacounty.gov.
Linda M. Ohara is a biology sciences lab technician at El Camino College in Torrance, CA, a
horticulturist, and a former nurserywoman. lohara@elcamino.edu.
Surendra K. Dara is IPM advisor for the University of California Cooperative Extension in
Ventura, CA. skdara@ucanr.edu.
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