10.6 Storage pests of tubers

We have already discussed the rotting and spoilage problems caused by fungi and moulds. Now the insect and animal pests will be discussed.

The major insect pest of the potato tuber is the Sweet Potato Weevil. It looks like the Rice Weevil shown on p. 170. The weevil often begins to attack the tuber in the ground before it is harvested. Then, when the tuber is carried to the store, the larvae, eggs, and adults are all carried to the store. Once in the store, they move into other tubers and spoil them. This weevil makes tiny, hard-to-see holes in the skin of the potato. However, fungus and other diseases can enter easily through this holes.

The best control method is to rotate the crop every two years so that the eggs which are laid in the soil will not find food when they hatch into larvae. They will die and soon the field will be free of the pest. Harvesting earlier than normal is helpful. The weevil likes mature, ripe sweet potatoes. Leaving the potatoes in the ground can be dangerous - the weevils can fly to fields where they know the potatoes are growing.

Insecticide - Malathion or Actellic - can be used if it is necessary. Check up in section 7.2, for information about chemical control of the Sweet Potato Weevil. The same rate of application should be followed with sweet potatoes as with grains.

Yams sometimes have a problem with termites in the field. Harvesting earlier is helpful. In storage yams sometimes are bothered by a weevil entering the tuber through the cut crown (where the sett was taken from). Rub wood ash on the cut before you store it. This helps to keep the cut free of fungi and insects.
If rats and other animals bother the tubers, trapping or harvesting early is the only control method.