Wednesday, July 26, 2017
University of Hawaii at Manoa
University of Hawaii System
College of Tropical Agriculture and Human Resources
 
Read our new publication: "Bacterial Wilt of Edible Ginger in Hawaii" (Oct 2013)

Symptoms of bacterial wilt of ginger include:
  1. "Green wilt" is the diagnostic symptom for the disease. This symptom occurs early in the disease cycle and precedes leaf yellowing. Green ginger leaves roll and curl due to the water stress caused by the bacteria that block the vascular systems of the ginger stems. 
  2. Leaf yellowing and necrosis. Leaves of infected plants invariably turn yellow and then brown. The yellowing should not be confused with another disease of ginger causing similar symptoms, Fusarium yellows. Note: Plants infected by the fungus, Fusarium oxysporum f. sp. zingiberi, do not wilt rapidly, as in bacterial wilt. Instead, infected ginger plants are stunted and yellowed. The lower leaves dry out over an extended period of time. Compare the symptoms of bacterial wilt and Fusarium yellows in this publication: C2-62.pdf.
  3. Plant stunting. Diseased plants grow poorly and may be stunted.
  4. Plant decline and death. Diseased plants can decline rapidly and die before harvest.
  5. Rotten rhizomes, often discolored. 
  6. Water-soaked appearance of infected rhizomes and stem vasculature.
  7. Discoloration of vascular tissues 
  8. Soft rots, caused by Erwinia spp.

E. E. Trujillo (1964, http://cms.ctahr.hawaii.edu/Portals/43/C2-62.pdf) accurately described the disease symptoms progress of bacterial wilt of ginger:

"The first symptoms of wilt are a slight yellowing and wilting of the lower leaves. The wilt progresses upward, affecting the younger leaves, followed by a complete yellowing and browning of the entire shoot. Under conditions favorable for disease development, the entire shoot becomes flaccid and wilts with little or no visible yellowing. However, the plant dries very rapidly and the foliage becomes yellow-brown in 3 to 4 days. Young succulent shoots frequently become soft and completely rotted and these diseased shoots break off easily from the underground rhizome at the soil line. The underground parts are also completely infected. Grayish-brown discoloration of the rhizomes may be localized if the disease is at an early stage of infection, or discoloration may be general if the disease is in an advanced stage. A water-soaked appearance of the central part of the rhizome is common.  In advanced infections, the entire rhizome becomes soft and rots. Bacterial wilt of ginger can be distinguished from other rhizome rots of ginger by the condition of the rhizome and the foliage. A better diagnostic feature is the extensive bacterial ooze that shows as slimy, creamy exudate on the surface of a cut made in the rhizome or on the above-ground stem of an infected plant."


Slideshow (above), with captions


Do you want photos of bacterial wilt of edible ginger? Here is a gallery of copyright-free photographs of bacterial wilt disease symptoms for free viewing and download: http://flic.kr/s/aHsjDNuVZN


Signs of bacterial wilt include: 
  1. bacterial streaming and 
  2. bacterial ooze from infected tissues, especially from infected rhizomes.

 
Signs of bacterial wilt of edible ginger
Left: 
Bacterial streaming from an infected ginger rhizome suspended in water. The streaming begins only a few minutes after placing the cut rhizome in water. This is a reliable assay for bacterial wilt. Right: Milky, bacterial ooze forming the cut surface of a discolored, infected ginger rhizome. The bacterial colonies may take one or two days to form, and form more rapidly in a humid environment. 
One may use either of these two signs of the pathogen to diagnose bacterial wilt of ginger caused by Ralstonia solanacearum.





Video: Overview of bacterial wilt

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