MSc

The present investigation on management of banana pesudostem weevil
Odoiporus longicollis Olivier (Coleoptera:Curculionidae) with induced resistance
and epideictic compounds was undertaken in the Department of Entomology,
College of Horticulture, Vellanikkara during 2000-2001. Extraction of epideictic
pheromone associated with the weevil, evaluation of the resistance of the moisture
stressed Nendran plants to the attack of the weevil and the resistance offered by the
progenies of tissue cultured plants of infested plants were considered for the study .
Females of 0. longicollis at different population intensities were
released on cut pseudo stem of Nendran in the laboratory to arrive at the minimum
pest load at which the concentration of epideictic pheromones would deter further
oviposition. The results indicated that the weevil numbers above five per
pseudostem was deterrent to conspecific emales.
Pest load which would deter oviposition on banana was also be
assessed by artificial confined release of females in the field. With increase in the
pest loads on the plants there was a deterrency effect in the oviposition by the
weevils. The maximum oviposition was observed by two weevils per plant (4.25).
Even with twenty females per plant the oviposition count was very less (1.75). The
oviposition deterrency was due to the deposition of the epideictic pheromone by
the conspecific females after egg laying.
It was seen that the acetone and ether extracts of pseudo stem pieces of
10 cm where five pairs of weevils had laid their eggs, when sprayed after air


drying and dilution with water deterred the oviposition by other females. The
acetone extract, air dried and diluted with water was the most effective for the
extraction of the pheromone. Identification of the chemical composition of
pheromones will help in their utilisation against the weevil.
No-choice tests were designed to study the resistance of moisture
stressed plants to the weevil attack. The weevil infestation was absent in those
plants which received the minimum quantity of water though their yield was low.
However, the plants which received slight reduction in the moisture (0.9 IW/CPE)
•. gave a yield similar to those plants grown with normal irrigation. Only 40 per cent
of these plants was infested when comparing with 90 per cent infestation in control
plants. Rind-pulp ratio was also in par with control plants. The results indicated
that the plants which receive a slight moisture stress from 6th month onwards at
least in the outer sheaths will escape :from the attack of the weevil without
affecting the yield adversely.
No-choice experiment was conducted on the progemes of infested
tissue cultured plants to evaluate the resistance to the weevil attack. The tissue
cultured plants was found very resistant to the weevil attack. The experiment was
started from the flower bud initiation stage (February). No plant was infested .upto
three months after artificial infestation. Infestation was noticed during rainy period.
The grades of infestation (0\ and O2) were very low in all the experimental plants.