Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Incidence, and effects on yield, of virus diseases of taro (Colocasia esculenta) in the Solomon Islands.

Abstract

Taro (Colocasia esculenta) on Malaita, one of the Solomon Islands, is affected by 2 virus diseases, alomae and bobone, both of which are spread by the delphacid Tarophagus proserpina (Kirk.). In localities where the diseases were endemic, plants of 284 cultivars died from alomae infection, and plants of 13 other cultivars showed symptoms of bobone on 3-5 leaves and then recovered, but 12-13% of them had a recurrence of symptoms. Loss of yield due to alomae infection was directly proportional to the percentage of plants infected. Losses due to bobone could not be reliably detected unless insect pests were controlled, such as Papuana inermis Prell, a beetle boring into the taro corms, against which 0.15% dieldrin was applied on some plots before planting. Frequent spray applications of 0.1% malathion against T. proserpina had no appreciable effect on the incidence of alomae, but fewer plants (30%) planted in November or December became infected than did those planted in May, June or August (64-94%). Since new taro crops are traditionally grown close to existing (and therefore possibly infected) ones, insecticidal control of the vectors will probably be of limited use in reducing the spread of these diseases.<new para>ADDITIONAL ABSTRACT:<new para>2 virus diseases, alomae and bobone, both of which are spread by the planthopper Tarophagus proserpina affect cocoyam on Malaita, Solomon Islands. Where the diseases were endemic, plants of 284 of 297 cv. died from alomae infection; the remaining 13 showed bobone symptoms on 3-5 leaves and then recovered, but symptoms later recurred on 12-13% of plants. Loss of yield due to alomae infection was directly proportional to the percentage of plants infected. Losses due to bobone of c. 25% could not be reliably detected unless insect pests were controlled. Frequent sprays with 0.1% malathion had no appreciable effect on the incidence of alomae, but fewer plants (30%) were infected when planted in Nov. or Dec. than when planted in May, June or Aug. (64-94%). Because new crops are traditionally grown close to infected crops, insecticidal control of the vectors will probably be of limited use in decreasing spread of the diseases.<new para>ADDITIONAL ABSTRACT:<new para>Much of this information has been noticed elsewhere [see PBA 48, 561]. Where the virus diseases alomae and bobone were endemic, plants from 284 of 297 varieties died from alomae infection; the remaining 13 showed symptoms of bobone on 3-5 leaves and then recovered but symptoms later recurred on 12-13% of plants.