M Sc

The study on “Documentation and management of Oriental fruit fly,
Bactrocera spp. (Diptera: Tephritidae) in banana” was carried out at the Department
of Agricultural Entomology, College of Agriculture, Vellayani during 2019 to 2021.
The objectives were to document the species complex and cultivar preference of
Bactrocera spp. infesting banana and to find out the effective management practices
against them.
Purposive survey conducted among 20 farmers each of two districts viz.,
Thiruvananthapuram and Kollam revealed that Palayankodan was the most
susceptible cultivar to the fruit flies followed by Red banana. High TSS (17.80°Brix)
of Palayankodan favoured the infestation. Fruit fly species infesting the banana
cultivars viz., Palayankodan, Red banana and Nendran was identified as Bactrocera
dorsalis Hendel. Bactrocera caryeae Kapoor was reported along with B. dorsalis
from guava.
Studies on the biology of B.dorsalis in banana under laboratory condition
revealed that egg, larva, pupa and total life cycle ranged from 1-3, 7-12, 7-10 and 51-
58 days respectively. Morphometric studies revealed that the average length and
breadth of eggs, full-grown maggots and pupae were 2.52±0.10 and 0.95±0.04 mm,
6.38±2.67 and 1.26±0.24 mm, 5.58±0.29 and 2.47±0.08 mm respectively.
The investigation on the assessment of critical stage of banana susceptible to
fruit flies was studied on Palayankodan fruits at different ripening maturity viz.,
under- mature, mature and over-mature. The critical stage of infestation by fruit flies
was identified as “over mature”. Significantly higher number of oviposition punctures
(13.30) and maggots (12.10) per banana finger was observed in “over-mature” fruit.
Though oviposition punctures was noticed in mature (6.90) and under mature (3.20)
fruits, no maggots were emerged from them. The tannin content in peel and pulp of
Palayankodan fruits at different ripening maturity was estimated using folin-denis
method to determine the defensive role played by tannin in the prevention of
B.dorsalis infestation. The highest tannin level was found on both peel (235.29 mg g-1
DW) and pulp (265.62 mg g-1 DW) of under mature fruits. In over mature fruits, both
peel (120.08 mg g-1 DW) and pulp (98.88 mg g-1 DW) recorded less tannin content
which supported oviposition and growth of maggots.
Laboratory experiment was laid out in CRD to study the efficacy of
treatments against B. dorsalis on Palayankodan immediately after the harvest. Among
various treatments, quinalphos 25 EC 0.05% was found to be the best treatment in
reducing fruit fly infestation in banana followed by spinosad 45 EC 0.02%,
azadirachtin 0.03% and salicylic acid 2mM. The oviposition deterrence recorded was
significantly higher in quinalphos 25 EC (97.03%) followed by spinosad 45 EC
(93.97%), azadirachtin (80.14%) and salicylic acid 2mM (63.44%). Presence of
residues of quinalphos (0.021 mg kg -1) and spinosad (0.069 mg kg -1) in banana at
the time of harvest was above MRL (0.01 mg kg-1), hence the next effective
treatment, azadirachtin (0.03%) which was on par with Spinosad could be
recommeded after harvest for the management of fruit flies in banana.
The study could be concluded that the species of fruit fly infesting banana
cultivars was identified as B. dorsalis and Palayankodan is the preferred cultivar and
the critical stage of infestation by B. dorsalis was “overmature”. Post harvest
spraying of azadirachtin (0.03%) was found to be effective and safe for the
management of fruit flies, B. dorsalis in banana.

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