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

Abstract

S U M M A R YTwo 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 AugustBecause 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.(64-94%).

A Review on Viruses Infecting Taro (Colocasia esculenta (L.) Schott)

“…However, another serological study found that bacilliform-like particles only exist in the insect vector, but not in the infected plants [46]. The virus latency would prove to be a challenge in diagnosis, as a small amount of virus could still remain in a community without exhibiting any symptoms, and, when combined with vegetative propagation, the virus could rapidly spread into the crop community [29].…”

“…As mentioned before, Alomae and Bobone are the major diseases infecting taro [5,28]. It has been found that the virus particles that are responsible for Alomae are only present in the male taro cultivars, whereas the ones responsible for Bobone only occur in female cultivars [28,29,61]. Additionally, the particle size in Alomae is smaller than the ones in Bobone, although the cultivars infected with Alomae often leads to death while Bobone-infected cultivars can recover [29,62].…”

“…Meanwhile, the widely studied taro diseases are Alomae and Bobone, which are found to be restricted to the Solomon Islands and Papua New Guinea [5,28]. Previous studies implied that the co-infection of two different viruses could result in symptomatic plants; co-infection of TaBV and CBDV result in the Alomae, while infection by CBDV alone results in the Bobone [5,29]. In addition, plants with Alomae symptoms are also found to contain another putative rhabdovirus, TaVCV, although confirmation tests for correlation are yet to be done [22].…”

Antimetabolic effects of plant lectins towards nymphal stages of the planthoppers Tarophagous proserpina and Nilaparvata lugens

“…Taro Colocasia esculenta (L. Schott), is a root crop which is grown throughout the tropics and sub-tropics. TPH acts as a vector for two rhabdovirus diseases, Alomae and Bobone, which are found exclusively in Papua New Guinea and the Solomon Islands (Rodoni et al, 1994) and can result in up to 100% and 25% yield loss respectively (Gollifer et al, 1978). In the South Pacific region taro is affected by the economically important insect pest, taro planthopper [Tarophagous proserpina Kirkaldy (TPH)].…”

“…Both insects also act as vectors of economically important viruses. TPH acts as a vector for two rhabdovirus diseases, Alomae and Bobone, which are found exclusively in Papua New Guinea and the Solomon Islands (Rodoni et al, 1994) and can result in up to 100% and 25% yield loss respectively (Gollifer et al, 1978). Neighbouring islands are major exporters of taro and virus-carrying TPH are a significant quarantine risk to the region.…”