Management of Seed Borer in Sapota: Life Cycle

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Life Cycle:

A female moth lays eggs on medium sized immature fruits of sapota when the seed coat is soft, thus fruits of marble-lime size with soft seed coat are the critical stage for seed borer infestation.

     Critical stage of fruit for seed borer infestation

 

         Seeds with soft seed coat

 

Larval  entry streak on seed coat

 

Black larval head capsule is seen in the hole on the cotyledons

 

Neonate larvae seen on slimy cotyledons

After hatching, the neonate larvae bores into the immature fruit. The larva nibbles through the raw pulp and enters the seed, when the cotyledons are still soft. During entry into the seed, it makes a streak on the seed coat that later disappears as seed hardens, rarely leaving a faint scar. The early instar larva is not easily detectable in the seed as it is transparent, and merges with the tender slimy kernel, and observable only through a microscope.

The larva completes its larval period inside the seed. In the seed, the larvae undergo perceptible colour changes from transparent to ivory color to dirty white to pink to stages of larval development and larva feeding on cotyledons brick red probably corresponding to five instars. The larva on entry feeds extensively on seed kernel and as a result, excreta is found in the damaged seed.

When larva turns brick red at late maturation, it emerges out by making a round hole through the hard seed coat. It tunnels through the pulp and emerges out on the fruit surface, leaving behind a pinhead size round to oblong hole (~0.1cm), the only evidence of infestation. For pupation, the mature larva comes out by tunneling out the fruit which usually coincides with the fruit harvest.

The larva that emerges out of a fruit cuts a leaf and folds it to make a fine shell-like structure within which it pupates. The pupae are obtect type, brown in colour and entangled in white silken material. The adult is a small elicate greyish white moth with bell shaped wings and esembles bird droppings. Head and thorax are white in Iolour with grey patches. Posterior dilation is observed in  forewings with brown edged orange spots at the apex and hind wings are pale whitish brown in colour. Legs and labial palps are very furry with long hairs. Adult moths are weak fliers and this may be the reason for their observed aggregated infestation pattern in the orchard. 

 

Source: Dr. P. D. Kamala Jayanthi and Dr. Abraham Verghese Division of Entomology and Nematology, IIHR, Bangalore

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