A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
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Pests and Diseases <strong>of</strong> Dipterocarpaceae 123<br />
not reduce the strength <strong>of</strong> timbers but degrades their<br />
quality and value (Thapa 1971, Hong 1980a, b). Stains<br />
can be caused by moulds, resulting in superficial staining<br />
easily brushed or planed-<strong>of</strong>f, and sap-staining fungi<br />
(‘blue-stain’), producing deep penetration stains. The<br />
most common are Diplodia spp., Ceratocystis spp. and<br />
Lasiodiplodia [Botriodiplodia] theobromae (Supriana<br />
1976, Hong 1980a, b, Charlempongse 1985). For<br />
prevention and control <strong>of</strong> stain, it is best, when possible,<br />
to process the felled timber within 1 to 2 weeks.<br />
Otherwise, chemical treatment is the only way, and the<br />
cut ends <strong>of</strong> logs should be immediately treated. The<br />
chemicals most effective against black stain and mould<br />
include the salts <strong>of</strong> chlorinated phenols (e.g. sodium salt<br />
<strong>of</strong> pentachlorophenol, SPP), and organic mercury<br />
compounds. These chemicals, effective against stains,<br />
have a low efficiency on green moulds (Hong 1980a,<br />
1981b).<br />
Physiological Disorders<br />
Very few studies have been conducted on physiological<br />
disorders such as frost, drought, poor drainage and fire<br />
damage, except in India on Shorea robusta (Davis 1948,<br />
Ram-Prasad and Pandey 1987, Raynor et al. 1941,<br />
Griffith 1945, Anon. 1947, Bagchee 1954).<br />
A <strong>review</strong> <strong>of</strong> the adverse factors that probably combine<br />
to cause serious dieback <strong>of</strong> Shorea robusta in Uttar<br />
Pradesh (India) was made by Ram-Prasad and Jamaluddin<br />
(1985) including deficient and erratic rainfall, low<br />
retention <strong>of</strong> soil moisture, nutritional imbalance <strong>of</strong> the<br />
soil, over-exploitation, unregulated grazing, fire and<br />
excess <strong>of</strong> removal <strong>of</strong> fuelwood.<br />
Mortality <strong>of</strong> Shorea robusta seedlings and young<br />
saplings due to frost was mentioned (Davis 1948, Ram-<br />
Prasad and Pandey 1987, Raynor et al. 1941 Griffith<br />
1945, Anon. 1947, Bagchee 1954). Frost initiates canker<br />
in advanced trees usually on the border <strong>of</strong> the <strong>for</strong>est<br />
facing the open lands and on the banks <strong>of</strong> perennial<br />
streams where the precipitation is heavy as dew or hoar<br />
frost (Bagchee 1954). Radiation frosts, creating<br />
frostholes by convection currents, kill saplings, create<br />
cankers providing the route <strong>of</strong> entry <strong>for</strong> heart-rot fungi<br />
and produce a moribund type <strong>of</strong> Shorea robusta which<br />
ultimately becomes the object <strong>of</strong> attack by many<br />
parasitic fungi and pests.<br />
Drought is also an important cause <strong>of</strong> S. robusta<br />
mortality (Pande 1956, Seth et al. 1960, Gupta 1961,<br />
Ram-Prasad and Jamaluddin 1985, Khan et al. 1986). In<br />
Malaysia, Tang and Chong (1979) have reported a<br />
‘sudden’ mortality <strong>of</strong> Shorea curtisii seedlings due to<br />
moisture stress. In India, Bagchee (1954) mentioned that<br />
the roots <strong>of</strong> Shorea robusta must be in the region <strong>of</strong><br />
permanent water zone in order to be healthy. On the other<br />
hand, Yadav and Mathur (1962) reported excess water<br />
accumulation during the rainy season caused mortality<br />
<strong>of</strong> S. robusta seedlings by development <strong>of</strong> white slimy<br />
growth on the roots and Sharma et al. (1983) reported<br />
deaths due to poor drainage.<br />
Fire, <strong>of</strong>ten <strong>of</strong> anthropogenic origin, can damage S.<br />
robusta (Joshi 1988, Ram-Prasad and Jamaluddin 1985,<br />
Sinha 1957, Bagchee 1954, Bakshi 1957). It results in<br />
de<strong>for</strong>mity and other injuries to the immature trees such<br />
as burrs, galls, tumourous knots, cankers, and heart-rot<br />
fungi entering through wounds.<br />
Management Aspects<br />
There are few practical management methods directly<br />
available to <strong>for</strong>esters against pests and diseases attacks<br />
in mature dipterocarp trees. Concerning pests, the main<br />
record is the ‘tree-trap’ technique set up in India <strong>for</strong><br />
reducing the population <strong>of</strong> Heterocerambyx spinicornis.<br />
Regular surveys <strong>of</strong> insect populations in <strong>for</strong>est<br />
plantations can help monitor the health conditions <strong>of</strong> the<br />
trees, and some insect species (Buprestidae,<br />
Bostrichidae, Cerambycidae, Scolytidae) are indicators<br />
<strong>of</strong> sickly trees (Stebbing 1914, Beeson 1941). So <strong>for</strong>est<br />
managers can identify which trees, providing shelters <strong>for</strong><br />
insect breeding, should be removed to avoid a massive<br />
infestation <strong>of</strong> trees and logs. The infection by heart-rot<br />
fungi on trees can be reduced by removing the dying and<br />
dead trees and burning them. The danger is more<br />
important if the tree bears fungal fruiting bodies and is a<br />
source <strong>of</strong> infection (Bakshi 1956a, b). The well-known<br />
technique <strong>of</strong> digging trenches around the infected areas<br />
to isolate the infected roots and soil area can also be<br />
applied.<br />
Bakshi (1957) suggested lowering the felling age <strong>of</strong><br />
the trees in <strong>for</strong>ests with a high incidence <strong>of</strong> heart-rot<br />
and to avoid coppicing from infested stumps. Heart-rot<br />
in the coppice standards due to Phellinus caryophylli<br />
and P. fastuosus is transmitted by grafting healthy roots<br />
with diseased ones or with decayed woody parts<br />
embedded in the ground. The disposal <strong>of</strong> slash should be<br />
a routine measure <strong>for</strong> protection <strong>of</strong> the stand against fire