MSc

A study was conducted know the efficacy of synthetic sex pheromone of
legume pod borer Maruca vitrata (F.) (Lepidoptera: Pyralidae) at College of
Agriculture, Padannakkad. Also investigated the female calling and mating behaviour
of the adult moths of M. vitrata. Response of commercial lure to male moths of the test
insect was studied in Electroantennogram at NBAIR, Bangalore.
The commercial synthetic pheromone lure of legume pod borer M.vitrata from
M/s Pest control India (P) Limited, Bangalore was tested and found that it failed to
attract not even a single moth. Subsequently, the mating behaviour of the moth was
undertaken in detail to investigate whether pheromones are involved in the mating
process of the insect. 30 per cent of moths emerged during photophase (6am-5pm) out
of which male moths constituted 36.25% and female moths constituted 23.75%.
During scotophase (6pm-5am), 69.68% moths emerged, out of which 63.12% was
males and 76.25% was females. The emergence found to peak at 5th and 9th hour of
scotophase.
During calling period female extrudes its pheromone gland beyond the
abdominal tip. Female calling behaviour of one to eight day old moths was observed
throughout the scotophase. A single calling peak was observed in all aged moths at 6 th
hour of scotophase except for three old day moths, which showed additional peaks of
calling at fifth, eighth and 9th hour of scotophase. For three-day-old moths, 43.5% was
the mean percent of calling at 6th hour of scotophase. The mating behaviour of 1-8 day
old M.vitrata moths involving 15 pairs throughout the scotophase showed maximum
mating percentage of 26.2 % and 16.6 % for 3 day old and 2 day old moths respectively.
Electroantennogram study conducted to know the response of 3-day-old male moths to
synthetic lure obtained from PCI, Bangalore showed that response to the stimulus was
0.05mv only, which was the same for the solvent hexane and the air.
75
This showed that there was no distinct physiological response for synthetic
pheromone lure. For further confirmation, GC-MS analysis was done and the
compound E, E-10, 12-Hexadecadienal was identified at a retention time of 16.42 min.
This is the major pheromonally active compound identified in previous studies. In GC-
EAD analysis, the response of M.vitrata male moths to E, E-10, 12-Hexadecadienal
was checked by matching EAD and FID peaks but without any response. So, the exact
reason for the absence of response to commercial synthetic lure is to be elucidated in
future studies for developing an effective commercial pheromone for the legume
spotted pod borer M. vitrata.