Contents - LAC Biosafety

338 Insect pests in plantations: case studies
(Chatterjee and Misra, 1974; Patil and Thontadarya, 1983b; Sudheendrakumar,
1986). In addition, five species of pathogens have been recorded. The parasitoids
include 26 species of tachinids, 19 ichneumonids, 17 braconids, 4 chalcidids,
3 trichogrammatids and one each of bethylid, elasmid, encyrtid, eulophid and
scelionid. Important insect predators are praying mantids, reduviids, carabids,
coccinellids and ants. A study in Karnataka in south India alone revealed the
presence of 43 species of parasitoids and 60 species of predators (Patil and
Thontadarya, 1983b), indicating the richness of natural enemies.
The microbial pathogens recorded are the fungi, Beauveria bassiana, B. tenella
and Fusarium sp., and the bacteria, Bacillus cereus and Serratia marcescens (Patil and
Thontadarya, 1983b; Agarwal et al., 1985; Singh and Misra, 1987). The LC50 value
for B. bassiana was 2.9 10 3 conidia for 3rd instar larvae and it increased with
increasing larval age (Rajak et al., 1993). This fungus was found to infest 29% of
larvae in a teak plantation in Karnataka, India (Patil and Thontadarya, 1981).
Control As discussed under Hyblaea puera, the biological control package
recommended against the teak defoliators from the 1930s to the 1980s in India
was also targeted against E. machaeralis, but it was neither put into practice nor
tested under field conditions. Similarly, the aerial spraying trials with
insecticidal chemicals carried out in India in the past (see under Hyblaea)
was also intended against E. machaeralis. However, no control measures were
practised, apparently because there was no proof of effectiveness and the
foresters were not convinced of the need for control. On the other hand, erratic
infestations in the nursery beds were controlled by remedial insecticidal sprays.
For reasons discussed earlier, it is essential to carry out a study on the impact of
E. machaeralis on the growth of teak plantations in a place where the insect
causes regular defoliations, before embarking on its control. The potential of
various control agents is examined below.
Parasitoids, predators and microbial pathogens Patil and Thontadarya (1983c)
tested 10 species of Trichogramma and found that all of them successfully
developed in fresh and one-day old eggs of E. machaeralis, in the laboratory. They
also tested (Patil and Thontadarya, 1984) three exotic species of Trichogramma,
that is T. evanescens, T. brasiliensis, and T. ‘pkcal’ (a hybrid), by releasing 5000
parasitoids of each in a moderately infested, three-year-old, 5-ha plantation and
obtained high recoveries for 60, 90 and 105 days respectively after release.
This suggests that Trichogramma spp. could be successfully used for controlling
E. machaeralis. Other promising parasitoids for biological control are the
braconids, Apanteles machaeralis, which parasitizes first to third instar larvae,
and Cedria paradoxa which parasitizes third instar onwards. C. paradoxa, which