Contents - LAC Biosafety

218 Insect pests in plantations: case studies
of tender leaves in the total foliage is relatively small (Beeson, 1941). Commercial
preparations of the bacterial pathogen Bacillus thuringiensis has been shown to be
effective against this insect (Kalia and Lall, 2000).
Knowledge gaps It is believed that in places with adequate subsoil water
level, the trees come into flush and possess mature foliage early in the season,
before the overwintering moths start laying eggs and thus escape attack as the
insect lays eggs only on tender leaves. Critical field observations are necessary to
establish the usefulness of this method of control. The possibility of the insects
adapting to the early flushing trees cannot be ruled out.
10.7 Eucalyptus species (Myrtaceae)
Tree profile
Eucalyptus is a widely planted tree genus in the tropics. Most species of
this genus of more than 600 species are endemic to Australia, where they occupy
various ecological niches from sea level to alpine zones and from moist to dry
areas (Wylie and Floyd, 2002). Three species, E. deglupta, E. urophylla and E. pellita
occur outside Australia. E. deglupta is native to Papua New Guinea, eastern
Indonesia and the Philippines (Mindanao Island); E. urophylla is native to Timor
and the adjacent islands and E. pellita is native to Indonesia (Irian Jaya), Papua
New Guinea and Australia (CABI, 2005). The adaptability of eucalypts to a variety
of site conditions, their fast growth, coppicing power and suitability for paper
and rayon grade pulp have made them well suited for short rotation plantations.
They are usually grown on a six to eight-year rotation, with two coppicing cycles.
Several species are planted in the tropics; the most common are E. camaldulensis,
E. globulus, E. grandis, E. robusta, E. saligna and E. tereticornis, all of Australian
origin, and E. deglupta and E. urophylla of non-Australian origin.
Although many species of eucalypts were introduced into the tropics earlier,
for various purposes, large-scale planting for pulpwood production began in
the 1960s in most countries. An estimate in the year 2000 put the global area
under eucalypt plantations at 10 million ha (Brown and Ball, 2000), although
some of it is in the subtropical zone. For example, eucalypt plantations occupy
3.1 million ha in India, 2.7 million ha in Brazil and 670,000 ha in the tropical
south of China (Brown and Ball, 2000; Wylie, 1992). Exotic eucalypt plantations
exist in over 80 countries and at least 20 species are grown on a
commercial scale. Tropical Australia had only a few thousand ha under eucalypt
plantations until recently, but the plantation area is increasing rapidly
(Wylie and Floyd, 2002).