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<Author> Keiji YASUDA |
The occurrence of the West Indian Sweet Potato Weevil (WSPW) and the damage it causes in sweet-potato fields treated and not treated with insecticide from planting to harvesting were surveyed. WSPW females invading the fields oviposited first in the stems, and the mean number of insects including larvae, pupae and adults in stems increased to 1.22-3.90 per plant in untreated plots. The first appearance in tubers was later than that in stems and the mean number of the weevils in the tubers increased to 5.04-7.97 per plant at harvesting. Stems damage by the WSPW larvae was found 30-60 days earlier than tuber damage in untreated plots. When the insecticide was applied topically on the ground near stems, the level of damage and number of WSPW did not increase as much in both stems and tubers. Damage to stems did not affect the growth of the sweet potato, and seemed acceptable. It is possible that the ratio of damaged stems can predict tuber damage and whether to apply insecticide or not. |
