Update on the Red Ginger Disease Complex

Russell Galanti

University of Hawaii,
College of Tropical Agriculture,
Cooperative Extension

Red flowering ginger (Alpinia purpurata) production in Hawaii is currently being affected by a disease complex consisting of several viral pathogens and possibly one or more fungal or bacterial pathogen. This is a widespread disease issue that has gone unchecked for many years. As of 2020 the research is focusing on categorizing the viruses and other pathogens, with some work being done on control methods. The following information outlines what is currently known about the disease complex as of July 2020.

Problem

  • Combination of virus and other pathogens
  • Possibly additional viruses beyond current identifications
  • Possibly combination of multiple other pathogens
  • Unknown disease-causing pathogens

Symptoms

Stunting and dieback
Plant height usually much taller (3’-10’)
Alpinia purpurata at UH Manoa campus

Current Understanding

Several (6) viruses are identified in symptomatic plants

  • Viruses reduce vigor of plants
  • No bacterial pathogens were present in symptomatic plants
  • Fungal pathogens identified
  • Phomopsis, Phoma, Fusarium, Bipolaris, Nigrospora, several unidentified

Current Work

  • Pathogenicity-Testing which of the pathogens isolated show the same symptoms
  • Identifying best management practices for controlling virus vectors
  • Fungicide and organic trials for fungal pathogens
  • Growing plants out for pathogenicity testing and treatment testing

Pathogenicity

  • Has occurred for Phomopsis, Bipolaris, Phoma, Nigrospora
  • Found to have zero pathogenicity
  • Is this because the plants are virus free?
  • Different genetics?
  • Too healthy?

Prevention

Fungal and Viral

  • Do not move infected plant material, begin clean
  • Keep equipment, vehicles, and work shoes sterilized when moving between sites
  • Removing any infected and dead plant material

Cultural

  • Maintain healthy plants
  • Reduce overhead irrigation
  • Avoid excess moisture and drought
  • Avoid excess fertilizing if fungal symptoms are present
  • High nitrogen encourages aphids, mealybugs

Physical

  • Destroy and Replace
  • Cannot treat virus infected plants
  • Can treat for fungal pathogens
  • Remove and replace plants that are above threshold
  • Soil sterilization

Chemical

Fungicides

  • Fungicides have shown effectiveness
  • Manzate only anecdotally proven to work

Insecticides

  • Broad spectrum not recommended for effects on beneficial insects
  • Soaps and oils
  • Supporting beneficial insects for aphid predation
Field treated with manzate