4. Sapota Seed borer

4. Sapota Seed borer - Trymalitis margaritas
    Biology
    • The mating of male and female moths was observed during evening hours between 7.00 to 11.00 p.m. and the period of coitus lasted for 8 to 13 minutes.
    • The pre-oviposition, oviposition and post-oviposition period lasted for 1.50 to 2.1, 1.0 to 2.0 and 1.0 to 2.2 days, respectively.
    • The fecundity was ranged from 29 to 255 with an average 161.8±77.236 eggs per female.
    • The incubation period varied from 10.35 to 12.25 days with an average of 11.16 ± 0.715.
    • The average percentage of eggs hatched was found to be 92.
    • The total period required for completion of larval development ranged from 10.75 to 13.75 days with an average of 12.33 ± 0.832 days.
    • The first instar larvae were very minute, white in colour with pinkish tinge, without distinctly segmented and hairless body.
    • The average length and breadth of first instar larva was 1.761 ± 0.038 and 0.692 ± 0.012 mm, respectively.
    • Fully developed larvae was pinkish in colour and it measured about 12.467 ±0.022 mm in length and 2.673 ± 0.013 mm in breadth.
    • The full grown larva stopped feeding come out of the seed and started folding the leaf with the help of series of silken threads to form a cocoon.
    • The pre-pupal period varied from 17 to 33 minutes.
    Sapota seed borer damage
    Sapota seed borer

    • The pupa was small, dark brown in colour and obtect.
    • The pupal period ranged from 10.0 to 15.0 days with an average of 13.15 ± 1.663 days.
    • The pupa measured from 7.61 to 10.10 mm in length and 2.6 to 3.6 mm in breadth.
    • The adult moths were small in size, having whitish forewings with grayish spots on it and fringed with hairs at the margins of the wings.
    • The hind wings were cream coloured with thick hairs at the margins.
    • The adult measured 7.1 to 12.0 mm in length, 2.1 to 2.6 mm in breadth.
    • The adult male lived for 3.25 to 6.0 days, while female moths lived for 4.0 to 7.0 days.
    • Total life cycle from egg laying to emergence of adults varied from 34.10 to 45.0 days with an average of 38.5 ± 3.117 days.
    Management
    • Sapota seed borer is an invasive pest that might have been accidentally introduced in India from Sri Lanka a decade back.
    • The seed borer attacks immature fruits and it is difficult to distinguish between infested and uninfested fruits prior to the emergence of larvae.
    • Tiny holes
    • Fruits with tiny exit holes are the only indication of seed borer infestation. During the tunnelling process, the larva drags out the excreta from the seed to the pulp.
    • Majority of the larvae emerge from the seeds after feeding on the cotyledons completely and prior to ripening of the fruit.
    • Small black ants inhabit such damaged fruits. The larva on exiting from the fruit cuts a leaf and folds it over to make a fine shell-like structure within which it pupates.
    • The adult is a small delicate greyish white moth with bell shaped wings and resembles bird droppings.
    • The seed borer incidence depends on the variety and availability of susceptible stage of fruits (marble-lime size fruits).
    • There is no variety that is completely resistant to the seed borer infestation.
    • After main fruiting season, the pre-seasonal stray fruits serve as source of survival during off season.
    • Thus, Sanitation is to be maintained for eliminating the sources of seed borer infestation.
    • Collection and destruction of the off season stray mature fruits after main harvest till November will bring down the pest incidence.
    • Erecting light traps in the field during cropping season will attract adult moths and will minimize the incidence.
    • Effective management of seed borer relies primarily on the stage of spray intervention.
    • The time of application is crucial in the management of seed borer.
    Spraying
    • First spray intervention should be made when the fruits are of small lime size and thereafter the sprayings should be repeated at fortnightly intervals during main fruiting season.
    • Alternating the sprays of Deltamethrin 2.8 EC at 1 ml/l and Bt at 1 ml/ at fortnightly interval will bring down the seed borer infestation.

Last modified: Saturday, 4 February 2012, 5:34 PM