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Class
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Insecta
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Order
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Coleoptera
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Family
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Chrysomelidae
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A number of species come under the common name of tortoise
beetles or tortoiseshell beetles. They are characterized by flattened,
spiny larvae and adult beetles with broad domed oval shaped elytra.
Seldom a serious pest, but
tortoise beetles can cause considerable defoliation during severe infestation.
Severe damage at the vegetative and root initiation stages may reduce storage
root yield.
Throughout Africa, Southern China, Southeast Asia. At least four species of
Aspidomorpha
and eight other Chrysomelidae have been recorded in East Africa. Several species
occur in Southeast Asia including Cassida circumdata and C. obtusata,
the green tortoiseshells; A. miliaris, the spotted tortoiseshell; A.
elevata, the golden tortoiseshell, and A. amabilis, with reddish
brown elytra; Laccoptera tredecimpunctata and L. philippinensis,
the 13-spotted and orange tortoise beetles, respectively. In south-eastern
USA, the golden tortoise beetle Charidotella bicolor is a common but
minor pest.
The young larvae scrape on the surface of the leaves leaving a pale or brown
translucent membrane. Older larvae produce round holes. When feeding in groups, irregular holes are
formed and can totally defoliate the plant. Adults
also produce round holes in the leaves. Occasionally attacks are
sufficiently severe to completely skeletonise the leaves, defoliate the plant
and peel the stems. However, usually damage does not affect yield.
Tortoiseshell
beetle (A. miliaris)
Egg
The creamy white eggs are housed in a papery golden brown
ootheca
of 10-25 layered membranes filled with three eggs each . The
egg is elongated measuring 1.5 to 2 mm long. The size of
ootheca
ranges from 8-13mm long and 8-10 cm wide.
Larva
Young larvae (first to third instar) are light brown with 2 rows of 5
square round black spots on the thoracic area and 7 rows of 2 narrow rectangular
spots black spots on the abdominal region. The narrow rectangular spots
split into two making 7 rows of 4 spots as the larva matures,
and the colour of the body changes to golden brown. The body is surrounded with
black spines. Mature larva measures 7-10 mm long and 3-5 mm wide.
Pupa The pupa
is yellow with darker shade along the body margin. The lateral spines of
the head, thoracic and the anterior part of the abdomen are reduced. The lateral
spines of the abdomen are compressed towards the posterior end . The
number of spots is reduce to one pair on the anterior most portion of the head,
one on each side of the head, two pairs on the thoracic area and 4-6 spots on
the posterior end. Pupa measures 10-12 mm in length and 5-7 mm in width.
Adult The adult
is a medium-sized golden tortoise beetle with broad transparent extension of the
elytra, 10-13 mm long and 9-13 mm wide. The elytra contain 4 of broad
black spots on the transparent extension of the elytra and 19 -23 small spots
for the female and 15-17 small spots for the male with a dark golden yellow
dorso-median line.
Green tortoise beetle (C. circumdata)
Egg
The egg is elongated, 1.5 mm which is 4 times longer than its width. The light
green egg is covered by translucent golden brown parchment-like membrane with
two longitudinal ridges.
Larva The larva
appears green, flattened, slug-like with two pairs of branched lateral fleshy
green spines per segment except on meso- and metathroax which has three pairs
each. The skin from the last moult is attached to a pair of subanal spines,
held upright and appears dark brown. Late instars change colour from green
to yellowish green, becoming more yellow near pupation. Mature larvae reach 5.5 mm.
Pupa The body is yellowish green, oval, flattened with
prominent prothoracic shield. The head is hidden and the abdomen has a single row
of whitish spines on margins. All the larval skins are attached to the
posterior end appearing as an irregular black mass.
Adult The
adult is a small tortoise beetle with
metallic greenish yellow body. The wings have 3 irregular longitudinal
black band with lateral extension like a shield. The middle black band on inner
margin of wing shares with opposite wing. The surface is pitted.
13-spotted
tortoiseshell beetle (L. tredecimpunctata)
Egg
The oval eggs measure 1 to 1.5 mm and are laid singly on the leaf surface. The newly laid egg appears yellow turning
golden brown when about to hatch. The egg is covered with orange brown
parchment-like membrane with a distinct flap on top.
Larva The larva is flat, yellowish to golden brown, and
possesses lateral fleshy spines. The spines are unbranched in the first instar
then becoming branched in the later instars. The exuvia after each larval
moults become attached to a pair of long fleshy subanal spines appearing as a
black mass of dirt and not distinct and differentiated as in Cassida
circumdata. Mature larva measures 7.5 mm.
Pupa The pupa is brownish orange. The anterior most pair
of thoracic setae is branched and the lateral fleshy setae of the abdomen
is greyish and unbranched. Dark brown mass consisting of larval exuviae
are still attached to abdominal tip.
Adult The adult
is a golden brown beetle measuring 6-8 mm with 11 black spots on the elytra and
2 smaller black spots on prothorax. The prothorax is enlarged to form a shield
with lace-like pattern on the surface. The mesothoracic wing is thickened with
shield-like extension of the margin and showing lace-like appearance on the
surface.
Tortoise beetles are widely distributed and often very common.
Tortoiseshell
beetle
The ootheca are deposited singly and glued onto the surface of the leaf. The
eggs hatch after 7-10 days. Newly hatched larvae feed by scraping the surface of
the leaf. The insect undergoes 5 larval instars, each instar lasts 5-7 days.
Earlier instars are highly gregarious and become less gregarious as they mature.
Pupal period lasts for a week. Adults live up to two months.
Green tortoise
beetle
The mated female lays around 250 eggs in 2 to 5 days after emergence. The eggs
are laid singly on either surface of the leaf and covered with the translucent
golden brown parchment-like membrane. Hatching of eggs occurs in 4 to 7 days.
The insect undergoes 5 larval instars, each instar lasts 1 to 6 days. After each
moult, the exuvium (cast skin) becomes attached to the spines and each succeeding exuvium is
distinct and attached to the preceding one. These cast skins are carried by the
larvae when feeding or at rest. When the larva is disturbed, it is placed over
the body and is used as protective shield. The length of the accumulated exuvia
becomes longer as the larva matures. The total larval development ranges from
7-26 days. The pupa becomes firmly attached with silken threads by its caudal
end to either surface of the leaf. The pupal period is 4-8 days. The total life
cycle ranges from 15-41 days. Longevity of adults lasts 2-29 days. The male to
female ratio of adults is 1:0:1.1.
13-spotted
tortoiseshell beetle
The mated female beetle starts laying eggs 3 days after emergence and lays
relatively few eggs, about 7 eggs. The eggs are laid singly in batches of 3 eggs
per group. The incubation period lasts 5 to 6 days. There are 5 larva instars,
each instar lasts 1-8 days with a total larval period of 7-30 days. The larva is
sluggish and rarely moved from its feeding site unless disturbed or when
changing feeding area. The larva carries the attached exuviae in an
upright position concealing the larvae when at rest. When about to pupate the
larva attaches itself firmly on the underside of the leaf. The pupa still
carries the exuviae attached to the subanal spines. Pupal period ranges from
3-10 days. The total life cycle is 14-46 days. Longevity of adults lasts up to 2
weeks. Male to female ratio is 1.9:1.0.
Sweetpotato is the main host, while other Convolvulaceae especially
Ipomoea triloba are alternative hosts. Other crops which have been
established as alternative hosts are coffee, beet, potato and various flowers.
Tortoise beetle damage is quite conspicuous, as are the adults and immatures
themselves.
Control of these pests is seldom necessary.
Cultural control
Removal of convolvulaceous weeds in the surrounding area may reduce their
numbers.
Several natural enemies including egg and larval parasites (Tetrastichus
sp., Eulophidae;Chalcidae) and predators (Stalilia sp., Mantidae) have
been reported in Southeast Asia.
Amalin, D.M. and E. A. Vasquez. 1993. A handbook on Philippine sweet potato
pests and their natural enemies. International Potato Center (CIP), Los Baņos,
Philippines. 82 p.
Ames, T., Smit, N.E.J.M., Braun, A.R., O'Sullivan, J.N., Skoglund, L.G. 1997.
Sweetpotato: Major pests, diseases, and nutritional disorders. International
Potato Center (CIP), Lima, Peru, 152 p.
Capinera, J.L. 2004. Golden Tortoise Beetle. Featured Creatures
Factsheet EENY-014, Entomology and Nematology Department, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of
Florida. http://edis.ifas.ufl.edu/IN140
Oudhia, P. and J. Ganguli, J. 1999. Outbreak of Tortoise beetle Aspidomorpha
miliaris F. (Coleoptera ; Chrysomelidae) in Chhattisgarh plains. Insect
Environment 5(3) : 110-111.
Shepard, B.M. G.R. Carner, A.T. Barrion, P.A.C. Ooi and H. van den Berg.
1999. Insects and their Natural Enemies Associated with vegetables and Soybean
in Southeast Asia. Quality Printing Co. SC. USA. 108 pp.
Hill, D.S., 1983. Agricultural insect pests of the tropics and their control
- 2nd ed. Cambridge University Press, Cambridge, 45 p.
Vasquez, E.A. and C. E. Sajise. 1989. Pests of sweet potato: Insects, mites
and diseases. PRIS and PRCRTC, Visayas State College of Agriculture,
Baybay, Leyte, Philippines. 66 pp.
Vasquez, E. A. 2002. Biology of Tortoiseshell beetle, Aspidomorpha
miliaris (F.), Chrysomelidae. Unpublished report. PhilRootcrops, Leyte State
University, Baybay, Philippines.
Contributed by:
Erlinda Vasquez and
Vilma Amante |
