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Sweet Potato

Sweet potato weevil

Symptoms of damage

Thickening and malformation of vines and often cracking of the tissue.
Discoloration, cracking, or wilting of damaged wines
An infested tuber is often riddled with cavities or tunnels
Attacked tubers become spongy, brownish to blackish in appearance
Start rotting form the top and develop an unpleasant smell and a bitter taste
Unfit for human consumption.

Identification of pest

Egg: Oval, yellowish-white laid singly in small cavities on the sweet potato root or base of the vine. The cavity is then sealed with a plug of the mother's excrement

Larva: Legless grub, white in colour. Head is comparatively large and brown or pale yellow

Pupa: Pupa is whitish in colour and pupation takes place in the feeding tunnel

Adult: Weevils are beetles with a long pointed snout, body is slender resembling ants

Management

Crop rotation with rice between two sweet potato
Use insect-free vines as planting material
Harvest the crop immediately after maturity
Avoid or minimise cracks in the soil
Flooding of infested fields for at least 48 hours after completing harvest drowns weevils induces rotting of the left over plant materials and thereby reduces weevil densities
Remove alternate host, Ipomea sp and destroy them.
Mulch with leaves of Eupatorium @3 tonnes/ha at 30 DAP
Use cut sweet potato tubers (100g) as trap during 50-80 DAP at 10 days interval
Set the trap at 5 m apart at 4 PM, collect and destroy adult weevils at 6 AM next day
Rake up the soil and earth up at 50 days after planting

Tortoise beetles

Symptoms of damage

Young grub scrape on the upper surface of the leaves
Older grub and adults bite large round holes in the leaves

Identification of pest

Grub: Oval, flattened yellowish with spiny processes covering the body.

Pupa: Is less spiny than the larva, and is fixed to the leaf

Aspidiomorpha miliaris: Broad oval shaped brownish red in colour With black dots

Cassida circumdata: Broad oval shaped, greenish yellow in colour with green crescent mark in middle

Chirida bipunctata: Small metallic green in colour with six black spots on elytra

Management

Collect and kill the grubs
Spray Malathion @ 200 ml/ac
Use insect-free vines as planting material
Use yellow sticky trap @12/ha
Spray Carbryl @1.25 kg/ha at 21 days interval at the time of harvesting sweet potato