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Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

Sweetpotato weevil (029)

Photo 1. Larvae or grubs of sweetpotato weevil, Cylas formicarius, damaging a vine at the crown where the stem enters the ground.

Photo 2. External damage to the base of the vine - called the crown - by the sweetpotato weevil, Cylas formicarius. Holes used by the adults to exit the stems can be seen.

Photo 3. Crown area of the vine, just above soil level, heavily infested by sweetpotato weevil, Cylas formicarius, and rots have developed.

Photo 4. Larvae or grubs of sweetpotato weevil, Cylas formicarius, in a storage root.

Photo 5. Adult sweetpotato weevil, Cylas formicarius.

Photo 6. Adult sweetpotato weevil, Cylas formicarius, caught in a sticky trap.

Photo 7. sweetpotato weevil, Cylas formicarius, on the outside of a storage root left on the soil. Note the small feeding pits made by the weevil.

Photo 8. A pheromone trap attracting large numbers of male sweetpotato weevils, Cylas formicarius. Note the trap is a plastic bottle with the top 1/3 cut off and inverted. The pheromone has been absorbed onto rubber tubing which is held in place by wire.

Summary

Worldwide distribution. On sweetpotato and wild Ipomoea (morning glory). An important pest.
Adults lay eggs in base of the stem ('crown') and in storage roots, and larvae tunnel through them. Adults eat the leaves and surface of the vines.
Damage is the same as done by West Indian weevil. Worse in dry times, and in light sandy soils.
Spread by adults on the wing, and in cuttings and storage roots.
Cultural control: early, deep rooting varieties; plant only tip cuttings; remove wild morning glory; hill-up, covering cracks during dry times; ideally, make one-time harvest; 3-4-year crop rotation; after harvest, collect and destroy vines and infested storage roots.
Chemical control: treat vines (bifenthrin); treat plants in field every 3-4 weeks (bifenthrin or fipronil).

Common Name

Sweetpotato weevil

Scientific Name

Cylas formicarius

AUTHORS Helen Tsatsia & Grahame Jackson
Photos 1,4,5,6 & 8 Russell McCrystal, Bundaberg, Queensland.

Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat for the Pacific Community.

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