Contents - LAC Biosafety

10.17 Tectona grandis (Lamiaceae) 339
has a limited distribution in northwest India, has been reared successfully in
the laboratory in India, released in some places in India and Myanmar during
1937–40 and 1971 and found to establish successfully (Thakur, 2000).
It is obvious that the parasitoids and predators must be playing an important
role in keeping the population of E. machaeralis in check under natural
conditions.
Commercial preparations of Bacillus thuringiensis have been shown to be
effective against E. machaeralis in laboratory tests (Misra and Singh, 1993;
Roychoudhury et al., 1994).
Chemical control Several chemical insecticides have been tested against
E. machaeralis in the laboratory and found to be effective. These include
monocrotophos, chlordimeform, quinalphos and formothion and the synthetic
pyrethroids, cypermethrin (0.0014%), deltamethrin (0.0018%) and fenvalerate
(0.0058%), with the LC50 values shown against them (Singh and Gupta, 1978;
Borse and Thakur, 1993, 1994).
Pheromone The sex pheromone of E. machaeralis has not been isolated.
It is unlikely to be effective for control during outbreaks because of possible
migration of the moths and the large numbers of moths present during
outbreaks.
Host plant resistance Several papers have examined the differences in
susceptibility to E. machaeralis among teak clones originating from different
Indian states. These are based on damage rating in laboratory feeding trials on
excised leaves, or in the field on clones assembled in Germplasm Bank, or both,
and the clones have been ranked according to the degree of susceptibility
(Ahmad, 1991; Mishra, 1992; Meshram et al., 1994; Roychoudhury et al., 1995 a,b;
Roychoudhury and Joshi, 1996; Roychoudhury et al., 1997b). A critical assessment
of the methods employed and the results obtained in the above studies show
that while some variability exists, there is no practically worthwhile resistance.
Leaves of more susceptible clones have been shown to have a higher protein
to polyphenol ratio compared to leaves of the less susceptible (Jain et al., 2000).
Susceptible leaves also tend to have higher water content than less susceptible
leaves (Roychoudhury et al., 1995 a,b). Under natural conditions, outbreaks
normally occur late in the growth season when the leaves are mature and
tough, but given the choice E. machaeralis larvae prefer to feed on younger
leaves, on which the larval growth is faster and the rate of survival is higher,
as noted earlier. Since the insect will accept leaves of lesser nutritional
quality under natural field situations, any resistance based on subtle differences
in nutritional quality that has been demonstrated in the above studies