Contents - LAC Biosafety

280 Insect pests in plantations: case studies
Natural enemies An ichneumonid parasitoid, Syzeuctus sp. has been
reported to cause about 36% parasitism of D. abietella infesting P. girardiana
(chilgoza pine) in Himachal Pradesh, India (Thakur, 2000). A bacterium Bacillus
licheniformis has also been isolated from diseased larvae (Thakur, 2000). From
D. rubella in the Philippines, two ichneumonid larval parasitoids and two chalcid
pupal parasitoids have been recorded; the ichneumonid Eriborus sp. was found
to infest about 54% of the larvae in some seasons (Lapis, 1987).
Control There is no effective control against Dioryctia spp. Insecticidal
sprays have been suggested for controlling infestation of shoots (Lapis, 1987;
Singh et al., 1988) and cones in seed orchards (Thakur, 2000).
The primary pheromone component of D. abietella infesting spruce cones
has been reported as (9Z,11E)-9,11-tetradecadienyl acetate, but in trapping
experiments the synthetic pheromone component was only weakly attractive
(CABI, 2005).
Studies in Cuba have shown some genetic differences in susceptibility of pines
to D. horneana. Pinus caribaea var. caribaea, P. cubensis and P. maestrensis were the
most damaged, while P. caribaea var. bahamensis, P. kesiya and P. tropicalis showed
no significant damage (Echevarria, 1985). Halos et al. (1985) also showed that
Pinus caribaea var. bahamensis was the most resistant of 11 pines screened against
shoot moths (including Dioryctria rubella and Rhyacionia cristata) in the
Philippines; similar results were reported by Lapis (1987). However, Pinus caribaea
var. bahamensis is comparatively slow growing.
Rhyacionia species (Tortricidae)
Rhyacionia (¼ Petrova) spp. are similar to Dioryctria spp. in habits, but
smaller. A typical example is Rhyacionia cristata, present in Southeast Asia.
The adult moth has a wingspan of 12 mm; the forewings are light orange to light
brown, with whitish bands along the length. Young larvae are yellowish and turn
brown as they mature (Lapis, 1987). The following species have been recorded on
tropical pines – R. cristata in the Philippines (Lapis, 1987), R. salweenensis (probably
synonymous with R. cristata, according to Speight and Speechly, 1982a) and
R. khasiensis in Thailand (Hutacharern and Tubtim, 1995), R. subtropica in
Guatemala (CATIE, 1992a) and Cuba (Hochmut, 1972b) and R. frustrana, common
to all Central American countries (CATIE, 1992a). R. frustrana is also common in
the eastern United States where it is known as the ‘Nantucket pine tip moth’
(it was first discovered and studied on Nantucket Island, Massachusetts)
(Berisford, 1988).
Life history Eggs are laid on the needles. Newly hatched larvae feed
externally at the base of needles for a few days and then bore into the upper part