Mycoplasma-like Organisms in Ipomoea batatas in the Solomon Islands

RESP-726

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

Two virus diseases, alomae and bobone, both of which are spread by the planthopper Tarophagus proserpina affect taro (Colocasia esculenta) on Malaita, Solomon Islands. Where the diseases were endemic, plants of 284 of 297 cultivars died from alomae infection; the remaining 13 showed bobone symptoms on three to five 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 November or December than when planted in May, June or August (64–94%). Because new taro 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

The occurrence and transmission of viruses of edible aroids in the Solomon Islands and the Southwest Pacific

The symptoms and distribution of virus diseases of taro (Colocasia esculenta) and other edible Araceae (Xanthosoma sagittifolium, Alocasia macrorhiza and Cyrtosperma chamissonis) in the S.W. Pacific are reported. Dasheen mosaic virus (DMV) occurred in many areas but, although two bacilliform virus particles that are damaging in parts of the Solomon Islands were found in some areas, with the exception of Santa Ysabel they did not cause the lethal disease which restricts the cultivation of some taro varieties on Malaita. DMV is transmitted by aphids and spread by vegetative propagation. The larger of the two bacilliform particles is transmitted by the planthopper Tarophagus proserpina and the smaller one by the mealybugs Planococcus citri and Pseudococcus longispinus. Hypotheses are proposed to explain our results and prospects for controlling these viruses discussed