Global Plant Protection News

FOOT ROT, SWEET POTATO – JAPAN

ProMED
http://www.promedmail.org

Source: Yomiuri [in Japanese, machine trans., summ. Mod.DHA, edited]
https://www.yomiuri.co.jp/national/20211104-OYT1T50109/

Sweet potato foot rot disease, which was first confirmed in Japan in 2018, has now spread to 21 prefectures. As a result, the yield of sweet potatoes decreased and the wholesale price increased. Farmers and traders are worried about the damage and hope the problem will be resolved as soon as possible. Local governments are collecting information on the outbreaks from the farmers.

Foot rot was found in Okinawa and Kagoshima prefectures in 2018; Miyazaki in 2019; 5 more prefectures, including Kochi and Shizuoka, in 2020; and 13 additional prefectures such as Hokkaido and Tokyo in the current 2021. The national yield showed a decrease of about 60 000 tons over the last year, which is a new record low.

[Byline: Ryo Imaizumi]
—
Communicated by:
ProMED
<promed@promedmail.org>

[The foot rot disease of sweet potato (_Ipomoea batatas_) in Japan referred to above is caused by the fungus _Diaporthe destruens_ (previously _Plenodomus destruens_; see link below). Since its 1st detection in the country, it has become a major concern for sweet potato producers there. Symptoms on the crop may include yellowing of seedlings, blackening of vines, stem rot, disintegration of the root system, tuber rot, wilting, and death of plants. Fungal survival in the field has been reported to be poor, so spread may mainly occur with infected cuttings used for planting. More research is needed on the biology of the fungus and the potential role of environmental factors in disease development.

_Diaporthe_ species and strains are known to be associated with stem canker diseases in a range of crops, for example soybean, sunflower, and blueberry. They can cause high yield losses and may also affect international trade due to associated biosecurity risks. The diseases are favoured by warm, humid conditions. The fungi overwinter on plant debris left in the field and can be spread with plant material, by mechanical means (wounds) and human activities, and via frost injuries. Disease management may include phytosanitation to remove inoculum (such as deep plowing of crop residues), cultural methods (crop rotation, wide row spacing), as well as fungicide treatments of crops and/or seeds. Resistant crop cultivars are available only for some of the pathogens.

In Japan, the related fungus _D. batatas_, which causes dry rot of sweet potato, is native and widespread in fields.

Maps
Japan:
https://www.nationsonline.org/maps/japan-map.jpg and
http://toursmaps.com/wp-content/uploads/2016/08/political-map-of-japan.gif (with prefectures)

Pictures
Sweet potato foot rot symptoms:
https://bugwoodcloud.org/images/768×512/1563367.jpg,
https://keys.lucidcentral.org/keys/sweetpotato/key/Sweetpotato%20Diagnotes/Media/Html/TheProblems/DiseasesFungal/FootRot/foot%20rot2a.jpg,
https://keys.lucidcentral.org/keys/sweetpotato/key/Sweetpotato%20Diagnotes/Media/Html/TheProblems/DiseasesFungal/FootRot/foot%20rot1.jpg and
https://keys.lucidcentral.org/keys/sweetpotato/key/Sweetpotato%20Diagnotes/Media/Html/TheProblems/DiseasesFungal/FootRot/footrotClark21.jpg

Links
Review and diagnosis of sweet potato foot rot in Japan:
https://doi.org/10.3389/fpls.2021.694053
Information on foot rot of sweet potato:
https://keys.lucidcentral.org/keys/sweetpotato/key/Sweetpotato%20Diagnotes/Media/Html/TheProblems/DiseasesFungal/FootRot/Foot%20rot.htm,
https://doi.org/10.1080/09670879309371763,
https://doi.org/10.1007/s10327-016-0661-z and via
https://plantdiseasehandbook.tamu.edu/food-crops/vegetable-crops/sweet-potato/
Information on some _Diaporthe_ species and diseases via:
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/diaporthe
_D. desturens_ taxonomy and synonyms:
http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=557213 and
http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=557213
Other fungal taxonomy via:
http://www.indexfungorum.org/names/Names.asp
– Mod.DHA

Thursday, 11 November 2021 15:36:21