A review of dipterocarps - Center for International Forestry Research

Pests and Diseases of Dipterocarpaceae 122
Infection by heart-rot fungi on hardwood trees occurs
through initial injuries caused by human activities (e.g.
tapping), fire, drought, frost and other mechanical causes.
These fungi establish themselves when the trees are
either young or overmature. Most of these fungi live as
saprophytes in jungle slash and become parasites when
conditions for infection are favourable (Bagchee 1954).
Trees with heart-rot can exhibit all the outward signs of
healthy and vigorous growth. Heartwood is progressively
decayed with age. Heart-rot in Shorea robusta can cause
much loss of timber (e.g., 9-13%, with nearly 73% of
the trees infected) (Bakshi et al. 1967). Bagchee (1954)
reported that nearly 80% of trees with deformities have
fungus-rot in their stems. Of Shorea javanica trees
tapped for resin in Sumatra, 10% showed carpophore
development on their trunks, indicating advanced
infection (Elouard 1991). The fungi entering through the
butt-scars and causing root damage contribute to
windthrown trees (Bakshi and Boyce 1959). Infection
by rot fungi is more frequent in the suppressed trees in
overcrowded forests than in the trees of thinned coupes
(Bagchee 1954).
Flower destruction and seed abortion may be a
serious problem for seed production under forest
management. However, there has been little research, and
the only record is Curvularia harveyi on Shorea
pinanga in Indonesia (Elouard 1991).
Parasitic plants, belonging to Loranthaceae, were
observed on Shorea robusta in India and Bangladesh
(Davidson 1945, Singh 1954, Ghosh 1968, Alam 1984)
and on S. obtusa in Thailand (Charlempongse 1985). The
parasites caused serious damage although the trees did
not die (Davidson 1945, Alam 1984). The trees tended
to form epicormic branching in some of the older
plantations. The only method of controlling infestations
of Loranthus appears to be eradication by lopping in the
cold weather (De 1945).
Forest Products
Diseases on forest products are primarily wood decay
and staining fungi (Bagchee and Singh 1954, Banerjee
and Sinhar 1954, Sivanesan and Holliday 1972, Hong
1980a, b, Shaw 1984, Balasundaran and Gnanaharan 1986,
Supriana and Natawiria 1987, Kamnerdratana et al.
1987). Most of them belong to the Basidiomyceteae and
can be categorised as white rot, brown rot and soft rot.
In white rot, both lignin and cellulose are attacked. In
brown rot, cellulose and hemicellulose are attacked while
lignin remains unaffected. In soft rot, cellulose is
removed like brown rot but the mechanism of action on
cell walls is different. The fungi causing soft rot belong
to Ascomycetes and Fungi Imperfecti and are restricted
to hardwoods (Supriana and Natawiria 1987). Decay of
timber occurs mostly after felling, on wood in service
and on industrial wood products. Likewise, on logs and
poles an important number of wood decay fungi have been
identified and control methods investigated. Most of
these fungi are weak pathogens, though some can also
infect living trees, e.g., Hypoxylon mediterraneum
recorded both on trees and wood attacking Shorea
robusta trees and hastening their death or preventing
recovery (Boyce and Bakshi 1959).
Decay fungi affect boats (Premrasmee 1956, Savory
and Eaves 1965) and wall framing (Singh 1986). One of
the most common decay fungi is Schyzophyllum
commune recorded in India, Indonesia, Thailand and
Philippines (Bakshi 1953, Bagchee and Singh 1954,
Mizumoto 1964, Supriana and Natawiria 1987,
Charlempongse 1985, Quiniones and Zamora 1987).
Various dipterocarp species, Shorea elliptica, S.
hypoleuca and S. laevis are highly resistant to
Chaetomium globosum (soft rot) and Trametes
[Coriolus] versicolor (Takakashi and Kishima 1973) and
Shorea siamensis is extremely durable against
Coniophora cerebella, Trametes [Polystictus]
versicolor and Daedalea quercina (Bavendam and
Anuwongse 1967). Shorea guiso, Hopea parviflora and
Vateria indica proved to be resistant to several fungal
species (Moses 1955, Balasundaran and Gnanaharan
1986). Veneer-faced, low-density particleboards
including Shorea particles, tested for its resistance
against Tyromyces palustris and T. versicolor proved to
be resistant (Rowell et al. 1989).
Treatments, heating, fumigants, Wolman salt, ascu and
borax, boliden K-33 and tanalith C. were tested on various
wood species against decay fungi. Copper-chromearsenic
(CCA) is the most widely used preservative in
Malaysia for wood protection, but organotins are better
since they have a higher fungicidal activity, provide a
higher protection against the marine toredo worm, are
less toxic towards mammals and more easily degradable
(Hong and Khoo 1981, Hong and Daljeet-Singh 1985).
Wood staining fungi infect logs in logging areas and
freshly sawn timbers in saw mills. A large amount of
money is spent each year on preservatives to overcome
this problem of staining (Hong 1981b). The staining does