New disease killing Wasabi crops in Japan
A recent report details a discovery in 2014 of a new disease found to attack Wasabia japonica plants.
This report was released in February 2017, some 3 years after the disease had destroyed in the region of 98% of the wasabi crop.
Prior to this date there was no indication that the plant pathogen Phytophthora drechsleri even attacked Wasabia japonica. This pathogen is commonly known as Phytophthora rot.
This plant pathogen on infected plants causes brown stem bases and rhizomes distinctly marked from the healthy green portion.
The brown lesions enlarge in size and girdle the stem. The portion of the plant above the lesion will dry out but remains attached to the plant.
As the disease progresses, patches of diseased plants become conspicuous in the field which are visible even from a distance. The roots of Phytophthora blight-infected plants remain healthy. However, serious root-rot can occur which also kills the plant.
The whole foliage can exhibit a blighted appearance under conditions of high humidity.
Phytophthora rot is sporadic in nature, but occasionally assumes epidemic proportions in places of heavy and frequent rainfall. High incidence is usually associated with poor surface drainage, estimated yield losses due to Phytophthora rot is 98%, since the affected plants dry up rapidly.
This what you need to look for on the rhizome and/or the petiole (leaf stem), The plant shown is NOT Wasabia japonica.
© Copyright Malcolm Storey 2011-2115
There is no known treatment for this plant pathogen in Wasabia japonica.
Potential avoidance
Prevention is the only possible treatment the Wasabi grower can use at this time, until such time as the scientists come up with a means of controlling this plant pathogen once it has arrived.
My recommendations are;
- Make sure that your plants are growing in well drained media.
- Ensure that excessive water is not used to irrigate or spray on the plants.
- The humidity around the plants is controlled and not allowed to rise for long periods.
- Since this pathogen has many hosts, ensure that the growing area and surrounding are kept clean and tidy and free from plants and grasses.
Wasabia japonica grown and processed by World Wasabi has been grown for over 25 years with no disease problems due to our growing methods. If you want to know more then go here.
Copyright: 2017 - Present; World Wasabi Inc., All rights reserved
Ref: Minoshima, A., Takeuchi, J., Ono, T. et al. J Gen Plant Pathol (2017). doi:10.1007/s10327-017-0703-1
