Contents - LAC Biosafety

288 Insect pests in plantations: case studies
Malaysia and the Philippines (see Chapter 1). The genus comprises about
350 species (CABI, 2005), but they have not received much attention as plantation
species. Most planting in the past has been experimental, mainly as enrichment
planting in logged-over forests, using wildlings. However, small-scale, conventional
plantations of a few species have been raised, since the 1950s, in
Indonesia, Malaysia and India. The species planted include the relatively
fast-growing Shorea javanica, S. leprosula, S. parviflora, S. selanica, and S. smithiana
in Indonesia (Cossalter and Nair, 2000), about a dozen species including
S. leprosula and S. parviflora in Malaysia (Appanah and Weinland, 1993) and
S. robusta in India.
Shorea robusta C.F. Gaertn. (commonly called ‘sal’ in India) which has a major
pest problem, is described in some detail here. The tree is distributed in over
10 million ha of forests in central and northern India, between latitudes 18°N
and 32°N, extending into the subtropical zone (Fig. 10.29a). It also occurs in the
sub-Himalayan tract of Nepal and Pakistan and in Bangladesh. The tree is
gregarious in habit. Under favourable conditions, the tree attains a height of
about 30 m. It grows at altitudes as low as 10 m to over 1500 m, and 1000–3000
mm rainfall. It can tolerate temperatures as high as 45°C and as low as 0°C.
It produces a hard and durable timber, used for various construction works,
railway sleepers and mining operations. When injured, the tree exudes a
resin called sal dammer, which is used as incense. Generally, sal has been
managed under a shelterwood system with natural regeneration. The tree
coppices well and coppice rotations of 40, 60 or 80 years are practised with
periodic thinning. Sal has been planted within its native distribution range
in India as well as in Hainan Island in southern China and Zimbabwe in
Africa (CABI, 2005).
Overview of pests
Insect pests of Shorea species include defoliators, sap-sucking bugs and
stem borers. Most information is available for Shorea robusta in India on which
about 145 species of insects have been recorded. However, except for the periodic
outbreaks of a cerambycid trunk borer Hoplocerambyx spinicornis on Shorea robusta
in India (see pest profile below) there are no major problems for Shorea species.
The most important pests are the following.
In the nursery, seedlings of S. javanica are killed by a sap-sucking bug, Mucanum
sp. (Hemiptera: Pentatomidae) in Sumatra, Indonesia (Intari, 1996) and seedlings
of S. robusta by the ‘seed and seedling borer’ Pammene theristis (Lepidoptera:
Eucosmidae) in India (Beeson, 1941). The latter hollows out the tap root and part
of the stem above ground; it also attacks young growing shoots, causing dieback.