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Sweet potato weevil on sweet potato

Cylas formicarius Moggo in Luganda language
  • Plant pest- free cuttings
  • Cuttings should be 25-30 cm long taken from a fresh terminal shoot with at least 3 internodes that are deep rooted with long necks because adult weevils cannot burrow below 1cm
  • After 30 days of planting, Close soil cracks in the mounds to prevent the weevils from getting access to the developing tubers
  • Keep fields weed free to avoid alternative hosts
  • Rotate sweet potato with 4 years of cereals
  • Plant early maturing varieties like Dimbuka, orange sweet potato, NASPOT 8,11,12,13 and others, so that harvest can be completed before the dry season when the soil will dry and crack and allow weevil to reach the tubers
  • Encourage predators of the weevil like ants, spiders , carabids earwigs by keeping hedgerows of flowering plants.
  • Look for adult sweet potato weevil. It’s a tiny snout beetle, ant like. It has a narrow head and body, long legs. The head and body are metallic dark blue, thorax and legs are red. The antennae are reddish-brown with a thick club at the tip
  • Inspect the crop regularly, at least once a week by checking base of vines for damage and holes
  • Look out for yellowing, cracking and wilting of vines
  • Consider chemical control if many adult beetles are present on the leaves, and/ or when crop damage is notable at crown area of vines
  • Place pheromone traps in the field at a radius of 280m to catch male weevils, if a single trap catches 10 and above in a week, consider chemical control every two weeks until weevil numbers drop below threshold.
  • Larvae have fat, legless, C-shaped bodies that are dirty white with a pale brown head. They are found in the tubers and basal 10cm of the vines, but by then action is too late
  • infested storage tubers/ roots appear soft, smelling and have external scarring or small darkened holes. Action is too late.
  • Remove all infested sweet potato vines and storage roots/ crop residues after harvesting and bury 2 feet deep
  • Harvest when mature and avoid piecemeal harvesting to reduce access of the weevil to the developing tuber
  • When using a pesticide or botanical, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, pre-harvest interval, max number of sprays, restricted re-entry interval
  • Always consult recent list of registered pesticides
  • Dip planting material/ vines in a solution of Diazinon based- products (Diazol 60EC at 40-50ml/ 20l of water for 10-15 minutes). Done by trained personnel to reduce risks . Non-systemic organophosphate
  • WHO acute toxicity class II (Moderately acute hazardous to humans). Care should be taken during operation and disposal as its toxic to water organisms, birds and pollinators.
  • Drench using Carbaryl based products eg. (Sevin 80ml/20L of water) and others at planting. This is done on the soil. Carbamate group
  • WHO toxicity class II (Moderately acute hazardous to humans). Care should be taken during application as its toxic to soil and water organisms and many beneficials.
  • Spray Fipronil or Bifenthrin -products every 3-4 weeks on the foliage. Pyrethroid group. For dosage look at the label
  • WHO toxicity class II. Moderately acute hazardous to humans. Very toxic to water organisms and pollinators. Post Harvest I 7-14 days
AUTHOR(S): Esther Ssettaala Nakibuuka: Mubende District local Government, phone no +256782726483.,

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