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Disease and pest resistance

There are many serious diseases and pests of taro in Hawaii. Limited published data is available for the relative resistance of the many taro horticultural varieties, and so this portion of the key is, at this stage, limited in its use. We recommend these publi9cations on taro diseases (Ooka, 1994; Uchida et al. 2002), for extensive information on taro diseases, and the CTAHR website for up-to-date information. This is, by no means, a complete list of the many serious and minor diseases and pests of taro.

Pythium "soft" rot Also called Pala or Palahi. A number of species within the fungal genus Pythium cause this disease which turns the flesh of the corm into a soft, mushy, often malodorous mass. Plants become stunted, with crinkled, spotted, and yellowish leaf blades. It is a serious disease of taro, particularly in acidic soils, which are inherently low in calcium (Trujillo, 2002).

Taro leaf blight Caused by Phytophthora colocasiae. Leaf blight can be recognized by the formation of purplish to brownish circular water-soaked spots on the surfaces of the leaves. A clear yellow liquid is exuded from the spot. For taro in dryland cultivation, this disease is influenced by climatic condtions, and is most severe in the wet season.

Taro pocket rot A serious disease caused by a Phytophthora species which causes small to medium-sized cavities on the corm. Click here for more information on this disease.

Dry rot This common dryland disease is caused by the fungus Sclerotium rolfsii. Affected plants are stunted, and the corms are rotted at the base where sclerotia (small, spherical reproductive bodies) develop (see Wall, 2000).

Hard rot ("guava seed") Kalakoa affected corms have bark-like skin, woody flesh, and patches of reddish brown which are walled-off vascular elements. The cause of this disease is unknown (Ooka, 1994).

Dasheen mosaic potyvirus Also referred to as DMV, this virus is transmitted by aphids and causes leaves to have a mosaic pattern along the veins. However, the quality of the corm is not affected.

Root aphids Patchellia reaumuri are a serious pest of dryland taro. The aphids feed on the developing roots, ultimately causing death of the taro plant. See Sato & Hara (1997) and Sato(2000) for more information.

Apple snail Pomacea canaliculata was originally imported from South America by the aquarium trade, and intoduced into taro lo‘i for sale as food to supplement income. However, in taro patches, the snails feed on all parts of the taro plant. Efforts to control apple snail in Hawaii continue (see Cowie and Ako & Tamaru for more information).

Root knot nematode Meloidogyne sp. cause stunting and chlorotic (yellow) dryland taro plants, with characteristic galls, swelling, and malformations on the corm and roots.

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