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

Mayhew and Newton (1998) have reviewed the
silviculture of S. macrophylla with special reference
to Sri Lanka. Most of the S. macrophylla plantations
in Sri Lanka have been established as mixed plantations
with teak (T. grandis L.) and Jak (Artocarpus
integrifolia Linn. f). Swietenia macrophylla is
successful in these mixtures but teak and Jak are
unable to compete effectively (Mayhew and Newton
1998).
The interim management plan prepared by the
Forest Department proposes three methods of establishing
S. macrophylla plantations (Sandom and
Thayaparan 1995). These are enrichment by underplanting,
enrichment by block planting and enrichment
by block planting with a nurse crop. Current
planting practices are enrichment planting in
degraded secondary forests and underplanting of
Pinus plantations for conversion to broad leaf
species, while research is being conducted on the use
of nurse crops (Mahroof 1999). Enrichment planting
consist of 2 m wide lines spaced at 5 m intervals in
secondary scrub forests with trees planted 3 m apart.
Planting stock is obtained by uprooting seedlings
(striplings) about 1 m tall from under older plantations.
Underplanting is carried out by removing
alternate rows of pine trees and striplings are planted
along the opened lines at 3 m spacing. After
planting, patch weeding and climber cutting is
carried out for 3 years. Underplanting of Pinus with
S. macrophylla has been researched and reviewed by
Weerawardane (1996).
During the establishment phase of mahogany
there are problems due to damage by wild animals
such as porcupine, wild boar and rabbits. Termite
damage to the root system also causes considerable
mortality. Some mortality is due to drought.
Sporadic incidents of Hypsipyla robusta (Moore)
attack can be found but do not pose a major threat
under the present planting practices of planting under
partial shade. Hypsipyla robusta becomes a serious
problem when mahogany is planted in open sites.
Damage by wild animals is considered the most
important hindrance to growth, followed by termite
damage, H. robusta attack and mortality due to
drought.
Khaya senegalensis (Desr.) A. Juss.
This species is a recent introduction to Sri Lanka
from Africa. Two mature stands (0.5–1 ha) have
been established in the intermediate rainfall zone.
Several trees in these stands are producing seeds and
growth has been very satisfactory. Recent investigations
have shown its suitability to drier regions
(Tilakaratna and Weerawardane 1992) and it is now
considered a priority species for the dry zone. It
5
requires more light than S. macrophylla and is
increasingly used for reforesting open sites in the
intermediate and dry zones, where forest cover is
more sparse.
Studies are continuing on provenance testing and
planting methods. Planting is continuing, using
locally collected seeds and commercial seed-lots
procured from external sources. Khaya senegalensis
is planted mainly as pure stands or mixed with other
local species in open areas. It is also used for underplanting
of Pinus caribaea Morelet. plantations.
Khaya senegalensis has become popular in social
forestry and roadside planting.
The most important hindrance to growth is
elephant damage in some districts. In the existing
plantations and trials, multi-stemming and heavy
branching has been observed. Sporadic incidents of
H. robusta attack have been observed in plantations
but the incidence of attack is so limited that it does
not pose a major threat at this time. It may become a
serious problem if incidence of attack increases in
the future.
Toona and Cedrela species
There is confusion in the proper taxonomic identity
of the Toona and Cedrela species planted in Sri
Lanka with determinations including T. ciliata M.
Roem., C. chinensis and C. serrata. It appears that
both Cedrela spp. are probably T. sinensis (A. Juss.)
M. Roem. Toona ciliata and Cedrela spp. have been
planted at elevations between 1000 m and 1800 m
principally in tea plantations. Cedrela odorata has
been planted in a trial in the low country intermediate
zone and appears to be growing well at
present. No further work on this species has been
done.
Currently, the Forest Department is using T.
ciliata as one of the species in mixed plantations in
the up-country. It produces good wood for furniture
and construction. It has been planted in tea estates
primarily as shade trees, but also in water catchments
and protective reserves in and adjacent to tea estates.
This species is naturalised and regenerates well such
that it can be seen growing in natural forests and
homesteads.
The greatest threat to T. ciliata is from dieback of
the trees which may be due to a pathogen. High
mortality of trees, including large mature trees, can
be seen in many areas. Shot-hole borer (Xyleborus
sp.) is found in dead and dying trees and is thought
to be the vector for a suspected pathogen causing
dieback. The beetle makes galleries in the sapwood
of living trees. Brownish discolouration can be seen
in the sapwood around the insect galleries. This
problem has become a very serious hindrance to