[4] The undersides of leaves have spots that look water-soaked or gray, and as they expand, blight forms and the leaf is destroyed within a few days.

[1] One characteristic feature found on leaves is the formation of bright orange droplets oozing out from above and below water soaked leaf surfaces.

As a result, oospores overwinter in soil, underground storage organs, or on leaf debris left in the field after harvest.

Finally, chlamydospores have been produced under ideal laboratory conditions in culture, and may also serve as a survival structure in addition to oospores.

[5] Upon infection, oospores that overwinter on leaf tissue and petioles give rise to sporangiophores which have lemon-shaped sporangia at their tips.

Germ tubes give rise to appressorium which form haustorium and allow the pathogen to extract nutrients without penetrating the host’s cell membrane.

Zoospores lose their flagella, become cysts, germinate and feed on the host via a germ tube, and produce more sporangia to continue the disease cycle.

[6] The slanted shape of the taro leaf encourages sporangia and zoospores to spread to other hosts via splash from rain.

[4] The pathogen grows voraciously in areas with high humidity and heavy rainfall in addition to an optimal pH of 6.5 and temperature of 28 °C (82 °F).

During less ideal conditions, such as low temperatures nearing 20 °C (68 °F) and high humidity, sporangia release zoospores for indirect germination.

P. colocasiae has been observed in Indonesia, China, India, the Philippines, Malaysia, Hawaii, Papua New Guinea, and the British Solomon Islands.

This practice has ultimately proved ineffective as the removal of leaves largely mimics the defoliating effects of the Taro Leaf Blight disease itself, and exacerbates the losses in yield already devastating the crop.

[5] Chemical control of P. colocasiae has offered some relief in the form of preventative sprays containing copper, manganese, and zinc.

The slanted shape of taro leaves, and prevalence of the crop in wet climates, necessitates numerous applications which may not be economically practical.

The systemic fungicide metalaxyl has also been found to be effective in controlling P. colocasiae, especially when applied in conjunction with the pesticide mancozeb at the first sight of disease symptoms.

[5] A recent study obtained promising results using Eucalyptus globus essential oil to combat P. colocasiae.

In 2013, researchers were able to confer resistance to the taro plant via the oxalate oxidase (OxO) gene gf2.8 of wheat (Triticum aestivum).

Taro export made up 58% of Samoa’s economy and brought in 3.5 million US dollars annually immediately prior to the epidemic in 1993.