Integrated Management Practices for Bacterial Wilt of Edible Ginger
Some of these practices require sufficient planning and may have significant costs in money, supplies, time and labor.
- Site selection. The site should be well-drained and having no previous history of ginger cultivation. Do not plant downslope from another ginger field, as the runoff rainwater water can carry the pathogen. Test the soil at a field site for the pathogen before planting by PCR or a bioassay. Select a site with consistent rainfall throughout the growing season, and with a drier period at the end of the growing season (before and during harvest). If a site has excessive rainfall, the waterlogged soil may foster soil-borne diseases such as root rot and bacterial wilt. Choose a site with gently sloping land to improve soil drainage during the rainy months.
- Planting. Avoid planting during very wet weather, as this promotes dispersal of the pathogen within fields in draining water and on muddy boots and tools.
- Site preparation. Hill the planting rows to promote aeration of roots and adequate soil drainage. Use clean, pathogen-free equipment. Prepare soil plowing and harrowing so that the site and soils drain well after rainfall.
- Plant pathogen-free seed. Plant disease-free ginger by using pathogen-free seed. Consult these CTAHR publication for more information:
- Limit site traffic. Strictly limit external traffic and unnecessary visitors into ginger fields, as the pathogen can be attached to soil adhering to truck tires or boots. Do not bring tools to the farm that have any soil attached, as soil can harbor R. solanacearum.
- Composting. Specify types of compost, time interval
- Organic soil amendments. Mulches and composts promote microbial activity that may suppress R. solanacearum by competition and/or antibiosis.
- Crop rotation. Rotate ginger with crops that are not hosts of the bacterial wilt pathogen, R. solanacearum. Such root/tuber crops include sweetpotato and taro. Insert more comprehensive list here.
- Soil drainage. Ensure adequate soil drainage and diversion ditches to prevent the runoff of infected water sources into fields that are down slope from an infected field.
- Intercropping. Intercrop ginger with crops that are not hosts of the bacterial wilt pathogen, R. solanacearum. Such root/tuber crops include sweetpotato and taro. Insert more comprehensive list here.
- Hot water treatment consisting of exposing seeds to a constant 50°C temperature for 10 minutes is effective in controlling nematodes. However, hot water treatments are not effective for disease organisms such as R. solanacearum that are already present inside the rhizome.
- Biofumigation is the use of essential oils to kill or suppress the pathogen. Such oils are a natural component of certain green manures crops such as mint, palmarosa, and lemongrass. When these plants are turned or plowed into soils several months before planting, they decompose and release the essential oils which are toxic to the pathogenic bacteria. Plant essential oils have potential to control bacterial wilt by eliminating the disease-causing bacteria in field soil. The results of a study by Paret (2010, see References at bottom of this page) show that palmarosa and lemongrass oils were effective in significantly reducing the bacterial wilt pathogen in both laboratory and greenhouse studies. In addition, "none of the essential oil treatments reduced the growth or yield of the edible ginger test plants. Palmarosa (Cymbopogon martini), lemongrass (C. citratus) and eucalyptus (Eucalyptus globulus) oils were investigated for their effects on Ralstonia solanacearum race 4, and their potential use as bio-fumigants for treating pathogen- infested edible ginger (Zingiber officinale R.) fields. Three concentrations of the oils (0.04, 0.07 and 0.14 % v/v) were evaluated by culture amendment assay, epifluorescence microscopy, and pot studies. Culture amendment assay indicated complete inhibition of growth of the bacterium on the medium with palmarosa and lemongrass oils at 0.07 % and above. At 0.04 %, both oils significantly reduced the growth of the bacterium compared to the control. Eucalyptus oil at all concentrations did not reduce the growth of the bacterium. Epifluorescence microscopic observations showed 95-100 % cell death when treated with palmarosa and lemongrass oils at all concentrations and eucalyptus oil at 0.14 % in a direct contact assay indicating its bactericidal effect. Eucalyptus oil treatments at 0.04 and 0.07 % had bacteriostatic effects on cells. The pathogen was not detected in R. solanacearum- infested potting medium after treatment with palmarosa and lemongrass oils at 0.07 % and above in any of the experiments. None of the treatments reduced the growth or yield of edible ginger."
- Biological control. Biological control of bacterial wilt of edible ginger currently is not a viable management practice. More research and development in this area are needed.
- Control other pests that create injuries in ginger plants, such as the lesser corn stalk borer (Elasmopalpus lignosellus). The injuries are infection courts for R. solanaearum.
- Perform on-time harvest, which minimizes crop exposure to the pathogen.
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