Insect-pests - Biology East Borneo

26 Insect Pests and Diseases of Major Plantation Species
Experience with extensive eucalypt plantations outside
Indonesia is similar. The buprestid borer, Agrilus
sexsignatus, which affected some plantations in the
Philippines, was restricted to plantations growing on
poor sites and a particular provenance. Two serious
pests of eucalypts of Australian origin, Phoracantha
(borer) and Gonipterus (defoliator), were accidentally
introduced into some eucalypt growing countries in
Africa and the Mediterranean where they spread rapidly
causing economic damage. Therefore, vigilance is
necessary against accidental introduction of these pests.
Nursery diseases can be kept in check by using
fungicides and appropriate nursery management
techniques. However, root disease affecting older trees
is a serious problem which is likely to be aggravated in
the future because inoculum build up will occur over
successive short rotations and there is no effective control
method. Root isolation by trenching around diseased trees
is practised but is costly and not fully effective.
Phytophthora sp. is one of the causative agents identified.
Phytophthora cinnamomi is a serious and widespread
pathogen of E. marginata (jarrah) forests in Australia,
with a wide host range (Keane et al. 2000). There is
urgent need for an in-depth study of the fungi associated
with root rot of eucalypts in Indonesia and to screen
Eucalyptus species and provenances for resistance to
root rot. Leaf diseases, e.g. Cylindrocladium spp., have
been a serious problem in humid tropical environments
in parts of Asia, but while some have been recorded in
Indonesia, e.g. Macrophoma sp., they are not yet
considered a potential threat.
4.10. Eusideroxylon zwageri
Indonesian common name: Ulin
Eusideroxlon zwageri (Lauraceae), also called ironwood,
is a highly valued indigenous timber species in Indonesia.
It is a monotypic species distributed in Sumatra,
Kalimantan and some adjacent islands (Kostermans et
al. 1993). It is one of the heaviest and highly durable
timbers and has a variety of uses. In Sumatra and
Kalimantan it is traditionally used for roof shingles.
Plantations are being established in South Kalimantan.
Insect pests
There are no records of pests on the living tree, but
seeds are damaged by insects (Kostermans et al.
1993). The wood is highly resistant to termite attack.
Diseases
No disease of the living tree is on record.
Threat assessment
Although there is very little plantation experience with
this species, available information suggests that there
is no threat of pests and diseases.
4.11. Gmelina arborea
Indonesian common name: Gmelina
Gmelina arborea (Verbenaceae) is exotic to
Indonesia, although the related G. moluccana occurs
naturally in the Moluccas (Yap et al. 1993). It is a
relatively fast growing species, which produces a
lightweight hardwood suitable for construction,
carving, etc. It also yields good quality pulp. There
are large-scale plantations in Sumatra (Riau, West
Sumatra, Jambi, South Sumatra and Lampung),
Kalimantan (West, Central, South and East
Kalimantan) and the Moluccas (Fig. 2.1). Small
plantations have been raised in Java.
Insect pests
No major insect pests have been found on G. arborea
plantations in Indonesia, although there are minor pests.
One of the insects consistently associated with it is a
carpenter worm, Prionoxystus sp. (Lepidoptera,
Cossidae). The larva bores into the stem of saplings,
feeds from within and weakens the tree. In East
Kalimantan, 5-70% of saplings may be infested
(Ngatiman and Tangketasik 1987) and it also occurs in
Java and Sumatra. Injecting the larval tunnel with
lubricant oil and plugging the hole was effective for
control (Pramono et al. 1998). One of us (K.S.S.N.)
observed at Sebulu, East Kalimantan about 80% of
saplings stumped to produce multiple shoots in a clonal
multiplication area, were infested by this borer. The
infestation is conspicuous because the larval frass
accumulates on the ground, at the base of the plant.
However, the damage is not serious. Multiple infestations
may weaken the saplings, but they are not killed, and
the insect does not build up in large numbers because it
passes through only one generation per year. Shoot
cuttings kept in the nursery for rooting were attacked
by an unidentified borer, possibly, Alcidodes ludificator
(syn. Alcides gmelinae) (Coleoptera, Curculionidae).
This small curculionid beetle bores into the young green