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Species Page

taro planthopper

Tarophagus colocasiae

Distribution

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Host plants / species affected

Main hosts

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Colocasia esculenta (taro)

List of symptoms / signs

Leaves - honeydew or sooty mould
Leaves - necrotic areas
Leaves - necrotic areas
Stems - discoloration of bark
Stems - external feeding
Whole plant - dwarfing
Whole plant - wilt

Symptoms

The taro plant Colocasia esculenta is mainly damaged by direct feeding in cases of heavy infestation by Tarophagus spp. Direct feeding damage is owing to sucking sap from phloem and/or xylem of the plant tissue, and the resultant mechanical damaging of the tissues. According to Waterhouse and Norris (1987), older leaves are especially affected. Swaine (1971) reports stunting and wilting of taro plants in Fiji caused by severe infestation by the taro planthopper, especially in the dry season.

Additionally, the role of the taro planthopper as vector of mostly fatal alomae and bobone virus diseases (both rhabdoviruses) has been reported especially from the Solomon Islands and Papua New Guinea (Gollifer et al., 1978; Jackson, 1980; Mitchell and Maddison, 1983; Waterhouse and Norris, 1987).

Prevention and control

Cultural Control

A considerable reduction of Tarophagus infestation is achieved by planting only clean stocks. As Tarophagus spp. are usually brachypterous and thus limited in their dispersal ability, infestation in new plantings is avoided if the clean stocks are planted away from old infested plantings. Burning of infested fields is not recommended as natural enemies will also be destroyed along with the pests.

Regulatory Control

It should be emphasized that the spread of Tarophagus spp. (and the subsequent spread of virus diseases) can be limited by avoiding international transportation of infested taro plants. Locally, only uninfested or disinfected taro stems should be used for crop establishment.

Biological Control

Waterhouse and Norris (1987) summarized biological control attempts on the Tarophagus species. The most effective biological control agent in several countries, especially in the Pacific, proved to be the mirid egg predator Cyrtorhinus fulvus. This bug was first introduced from the Philippines to Hawaii in 1938, and successfully reduced the pest status of Tarophagus within a short time to a very low level (Fullaway, 1940; Waterhouse and Norris, 1987). Introduction of this predator was not successful in a few cases; e.g., Hawaii to Tahiti, Samoa to the Solomon Islands, and Fiji to Tuvalu (Asche and Wilson, 1989a). However, its presence on these islands has been confirmed (see Waterhouse and Norris, 1987). The origin of the predator is unknown but for Western Samoa it was known to be present before its deliberate introduction. Asche and Wilson (1989a) suspected that variation in the rates of success in using C. fulvus may be due to the different Tarophagus species involved in the different locations. The egg-parasitoid wasps Aprostocetus megameli and Anagrus perforator, as well as the nymph-parasitoid wasp Haplogonatopus vitiensis, play a less successful role in the biological control of Tarophagus species.

The egg-predatory bug Tytthus mundulus, introduced in Hawaii from Queensland, Australia in 1920 to control the sugarcane-planthopper Perkinsiella saccharicida, proved to be less specific and effective (Zimmerman, 1948). Similarly non-specific is the dryinid wasp Haplogonatopus vitiensis, a parasitoid especially attacking the larval instars, which was introduced from Fiji and liberated in Hawaii in 1904 also for control of P. saccharicida (Zimmerman, 1948).

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


This information is part of a full datasheet available in the Crop Protection Compendium (CPC);www.cabi.org/cpc. For information on how to access the CPC, click here.

Impact

Tarophagus spp. are a major pest of Colocasia esculenta, both by direct feeding and as vectors of the rhabdoviruses Alomae and Bobone (Francki et al., 1981; Mitchell and Madison, 1983; Ooka, 1983). The economic impact caused by Tarophagus spp. is difficult to assess; however, the heavy infestation of taro in Hawaii in the early 1930s was so severe that "the torch was applied to large areas of taro" (Zimmerman, 1948). Before control measures had been taken by introducing Cyrtorhinus fulvus, Tarophagus sp. had nearly destroyed the entire crop (Fullaway, 1940). For further notes on the pest significance of Tarophagus in Hawaii see Matsumoto and Nishida (1966). Outbreaks of Tarophagus reaching pest status have been reported from Samoa (e.g., Dale, 1959), Fiji (Hopkins, 1927; Swaine, 1971; see also references in Waterhouse and Norris, 1987), and the Solomon Islands (Jackson, 1974; Gollifer et al., 1978). Local outbreaks are known from the Philippines, Guam, Ponape, Papua New Guinea, Vanuatu, Tonga, Tuvalu, Wallis and Futuna, and French Polynesia (see references in Waterhouse and Norris, 1987).

The virus diseases transmitted by the taro planthopper can become extremely severe, especially in Papua New Guinea, the Solomon Islands, Vanuatu and Pacific Islands. Under experimental conditions, an infection of Alomae virus killed 284 out of 297 taro plants (Gollifer et al., 1978). Crop losses due to Bobone virus disease in New Guinea and the Solomon Islands could be as high as 25% (see references in Waterhouse and Norris, 1987).