Pacific Pests, Pathogens, Weeds & Pesticides - Online edition

Pacific Pests, Pathogens, Weeds & Pesticides

Lega o lau talo (Taro leaf blight) (014)

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Photo 1. Spots of taro leaf blight at the margins and inside the leaf blade. Note that some of the centres of the spots are falling out. Many have a characteristic yellow margin, or halo.

Photo 2. A taro leaf blight spot showing where the spores are formed at the margin.

Photo 3. The spore of the water mould, Phytophthora colocasiae, has a characteristic shape to the top (arrow). 

Aotelega

  • Aafia ai le lalolagi atoa. Aafia ai lau o talo ma isi auaiga e pei o le taamu. O se faama'i taua.
  • O le lega e ola i siosiomaga malu ma susu, o le oomycete, ae le o se ga'o. E vave ona faatamaia lau talo ma le lelei ai i’o o talo.
  • E amata ona aafia I’o o talo I le taimi o le seleselega, e faasolo ai ina pala ma enaena.
  • E sosolo le lega ma aafia ai isi talo I taimi timutimu, ma feaveai solo I meatoto poo tiapula.
  • Metotia Faalenatura: Faamamao ese fa'ato'aga, mai fa'ato'aga ua aafia I le lega, e sili atu i le 500 m; aloese mai le totoina o tiapula ma lautalo; siaki ma vaai lelei I taimi uma, ma aveese laulaau ua afaina; se’I ma fafai talo I taimi la ma mago pe matu lautalo; teu talo i taga pepa (po o pusa ua laina e taga pepa); ituaiga talo e mafai ona tete’e atu le lega.
  • Faogaina o Vaila'au: kopa, chlorothalonil, pool le mancozeb (puipuiga); metalaxyl po'o le phosphorous acid (systemics).

Igoa masani: Lega o talo.

Igoa Faasaienisi: Phytophthora colocasiae.

Photo 4. Droplets associated with taro leaf blight spots on the underside of the leaf which hardens into pellets as they dry. Leaf spots of other fungi infecting taro do not do this.

Photo 5. The underside of a taro leaf blight spot showing the liquid which 'bleeds' from the leaf when it is infected; this liquid dries during the day and becomes hard and dark brown. 

Photo 6. The spots are not only very large on this susceptible variety (Niue) in Samoa, but they have joined together to form a blight.

Photo 7. A brown firm rot in the top part of a corm caused by the water mould, Phytophthora colocasiae. The white cottony growth at the lower left side is caused by the fungus Athelia rolfsii.

Diagram. Life cycle of Phytophthora colocasiae. Note that the sexual phase of the life cycle has not been seen in Pacific island countries; this is because two mating strains are needed to form the oospore, and only the A2 strain has been found. The oogonium and antheridium are the equivalent to female and male parts which fuse to form the oospore (or resting stage).

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