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Crop Protection :: Pests of Sweet Potato

Sweet potato weevil: Cylas formicarius

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

 

Larval feeding Infested tuber
Larva


Adult


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

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