You are here

Error message

  • Warning: Cannot modify header information - headers already sent by (output started at /base/nariweb/index.php:1) in drupal_send_headers() (line 1225 of /base/nariweb/includes/bootstrap.inc).
  • Warning: Cannot modify header information - headers already sent by (output started at /base/nariweb/index.php:1) in drupal_send_headers() (line 1225 of /base/nariweb/includes/bootstrap.inc).
  • Warning: Cannot modify header information - headers already sent by (output started at /base/nariweb/index.php:1) in drupal_send_headers() (line 1225 of /base/nariweb/includes/bootstrap.inc).
  • Warning: Cannot modify header information - headers already sent by (output started at /base/nariweb/index.php:1) in drupal_send_headers() (line 1225 of /base/nariweb/includes/bootstrap.inc).
  • Warning: Cannot modify header information - headers already sent by (output started at /base/nariweb/index.php:1) in drupal_send_headers() (line 1225 of /base/nariweb/includes/bootstrap.inc).
  • Warning: Cannot modify header information - headers already sent by (output started at /base/nariweb/index.php:1) in drupal_send_headers() (line 1225 of /base/nariweb/includes/bootstrap.inc).

How to reduce damage from sweetpotato weevil

Sweetpotato weevil, the worst insect pest of sweet potato or kaukau, is reportedly causing great harm in PNG gardens. The weevil ruins storage roots (tubers) which rot with bitter taint. Immature larvae of the adult weevil makes tunnels and holes. When infected with larvae, even pigs won’t eat the storage roots.

The weevil especially likes dry conditions as the ground may crack and allow adults to easily lay eggs in developing kaukau tubers. The eggs hatch into little (1-2 mm) white larvae, that are easily seen. Adults hide and are hard to find. They look like ants with a long nose.

There is no easy way to control sweetpotato weevils. However there are cultural methods which can reduce weevil damage.

The first thing farmers can do is 'crop rotation'. Because weevils only eat plants from the sweetpotato family (Convulvulaceae), if we have an area that has no sweetpotato for about two years, the weevil population will decline to an acceptable level.

Use live fences to help slow down the movement of flying weevils from an area full of weevil into an area that has been growing taro, banana, sugar, corn, pumpkin, tapiok, peas, soybeans and so on, for about two years. That area must have no sweetpotato or alternate hosts. The weevils are not good at flying. Live fences can help to reduce their ability to infest clean sweetpotato.

When a farmer throws weevil damaged tubers into the base of a new sweetpotato mound there’s a chance that some adults will hatch and move through the dry soil to start infecting the new planting. Weevil damaged tubers should be burned or put in a bucket of water to soak and rot and stink for 10 days or so. Weevil eggs, larvae and adults will drown.

If wild sunflower is used in the new mound as compost material – this may help to reduce weevil damage. Research is needed to really find out what compost material will reduce or kill weevils in new kaukau mounds.

When the farmer brings kaukau vines from an old garden to plant into the new kaukau mounds, it is possible to bring weevil with the new vine. The adult weevil may already have laid eggs near the base of these vines. Clean vines, that have no weevil eggs are crucial. If in doubt, use just short vines, as the eggs are normally near the base of the vine. Small holes filled with faecal material are a sure sign of infected vine. NARI is making available totally disease free and weevil free sweetpotato vines.

PNG farmers like to make very clean, new kaukau mounds. Those clean mounds are open to hot sun which harms the soil, heavy rain which washes the soil away down river, and it is very easy for the weevil to find its way to new sweetpotato fields. If the farmer is smart and hides the mound by using lots of leaves of wild sunflower, or white flowering fish poison shrub (Tephrosia), or Neem which has insecticide properties or the shrub legume – Flemingiaor or any other leaves – these will help to reduce weevil damage.

The weevil likes to live in dry soil. If the farmer can water the kaukau mounds the weevil population will decline, just as it does normally in wet weather conditions. If the soil is waterlogged, there is no easy air for the insects to breathe. They drown in really wet soil. Cover any exposed storage roots with soil to hide the storage roots from the weevil.

Harvest sweetpotato a little bit early, before damage occurs.

Morning glory flowers sometimes grow on fences in a village. These are from the same family of plants as sweetpotato and the weevil can survive and multiply on these alternate hosts. Weed those out of your fence.

NARI has been doing lots of research work on new taro, tapiok, corn, rice, yam plants. These plants can add diversity to PNG family diets and will reduce the effects of sweetpotato weevil. Remember the weevil only affects sweetpotato.

Although there is no effective method to manage the weevil, the impact can be minimised if farmers follow these steps.

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer