Hypsipyla Shoot Borers of Meliaceae in Sri Lanka - Australian ...

The only harvesting of Swietenioideae in the foreseeable
future will be from plantations. Native
(T. ciliata and C. tabularis) and exotic (Swietenia
macrophylla King and S. mahagoni Jacq.) species of
Swietenioideae are being planted in plantations in
the hill country and also in village groves (Tables 2
and 3). Swietenia spp. are the most commonly
planted meliaceous species and are often established
in open spaced areas as block plantings or as strip
plantings along highways, railway lines, roadsides
and embankments. In block plantings, they are
usually planted in monoculture while in strip plantings
they are mostly in mixtures with other species.
T. ciliata is planted both in forest and in village
groves, whereas C. tabularis is exclusively planted
in the hill forests.
Severe damage caused by the shoot borer,
Hypsipyla robusta (Moore) (Lepidoptera: Pyralidae)
has been the major hindrance to growth of species of
Swietenioideae. However, the incidence of the collar
borer, Pagiophloeus longiclavis Marshall (Coleoptera:
Curculionidae) has also been observed in some
plantations of Bangladesh. The larva of the latter
tunnels in the cambium and sapwood causing
swelling and cracking in the collar region of the host
plant.
No data have been collected on the growth, yield
or economic performance of species of Swietenioideae
in Bangladesh.
Hypsipyla robusta Research and Future
Directions
In Bangladesh, no research on H. robusta has so far
been conducted apart from the work of Beeson
(1919, 1941) which covered many parts of the then
British India (now India, Bangladesh and Pakistan)
and the adjoining countries. Table 4 summarises the
adequacy of knowledge of various aspects of
H. robusta ecology and management. In spite of the
paucity of data on this pest, it is considered a major
problem in Swietenia spp. plantations in Bangladesh
(Baksha 1990, 1993; Baksha and Islam 1990).
Baksha provided brief notes on the pest and its
control measures. Beeson’s earliest work recorded
H. robusta infesting T. ciliata and Swietenia spp. in
the southern Asian region (Beeson 1919) and was
followed by his monumental synthesis of all available
information on this pest (Beeson 1941). However,
he did not mention specifically the occurrence
of this pest from anywhere in the territory now
known as Bangladesh. This could be due to the fact
that Swietenia spp. were not planted extensively in
Bangladesh until the independence of the country in
1971, following which plantation establishment
gained momentum.
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Table 4. Summary of current and past research effort on
various aspects of Hypsipyla robusta (Moore) biology and
control.
Area of study Current
research
– none; * minor; ** major.
Historical
research
Biology
Taxonomy – –
Life history ** *
Ecology in natural stands – *
Ecology in plantations ** *
Population dynamics ** –
Natural enemies * –
Other
Control
– –
Biological control * –
Chemical control ** –
Silvicultural control ** *
Provenance trials – –
Pheromone studies – –
Genetic engineering – –
Other – –
A detailed description of the biology and ecology
of H. robusta, based on various published sources
including Beeson (1941) is presented in Griffiths
(these Proceedings). However, a number of specific
aspects of the pest’s biology and impact on host
plants that have been recorded in the southern Asian
region are now outlined. In India, the length of the
insect’s lifecycle varies from one to six months
depending upon the season and it usually overwinters
as a fourth instar larva. In equatorial climates,
breeding appears to be continuous throughout the
year, with overlapping generations. Larval feeding
can cause considerable seed loss, particularly in T.
ciliata, but its importance lies mainly with its activity
as a shoot borer (Browne 1968).
Hypsipyla robusta passes through three distinct
generational feeding phases in T. ciliata in northern
India and Myanmar. The first generation feeds on the
flowers, the second on the fruit, and the third, fourth
and fifth on the shoots. In the flower and fruit generations,
pupation occurs in sheltered places, whereas
in the shoot generations, a pupal chamber is formed
in the larval tunnel. In southern India and Sri Lanka,
H. robusta only feeds on shoots.
Infestation is heaviest on young, vigorous trees
growing in full sun. The host is rarely killed; however,
retardation of growth in early years is serious.
Plantations in their second and third years are generally
most heavily attacked. Heavy infestation with
repeated destruction of terminal buds results in
crooked and highly branched stems.