PEST MANAGEMENT DECISION GUIDE: GREEN AND YELLOW LIST
Bacterial blight of cassava
Xanthomonas axonopodis pv manihotis (Syn. Xanthomonas campestris) Bacterial blight of cassava
- Bacterial blight is a soil borne bacterial disease that spreads through water splashes, mechanical damage and insect feeding (e.g. grasshoppers).
- Clean and disinfect farm tools before using them on another farm.
- Infected farmlands must be allowed to fallow for 2-3 years before planting cassava again. During the fallow period, cereals, grains or legumes can be planted.
- Use of healthy planting materials from research institutes e.g. International Institute for Tropical Agriculture and certified sales outlets.
- Use of resistant varieties like TMS30572, TMS91/02316 and 94/0026.
- Disinfect cuttings by immersing in hot water (roughly 60°C) for 20 minutes before planting.
- Intercrop with maize, sorghum or coco yam.
- Planting materials infected with bacterial blight must not be moved into other farming areas.
- Quarantine: cassava varieties from other countries must be tested before importation.
- In potassium-deficient soils, increase use of fertilizers to increase potassium content in leaves to reduce the potential disease severity.
- Pre-planting: check stem cuttings at vegetative stage for small green spots and lesions, from a month after planting onwards.
- Check for white oozing when stem slices are immersed in water. Discard infected cuttings.
- At vegetative stage (2 months onward), check both upper and lower sides of leaves. Look for gummy exudates from wounded leaves and stems. Discard such plants.
- Look for symptoms like scattered or grouped brown spots with yellow patches on leaves.
- Observe moist regions around leaf spots.
- Look for fallen infected leaves and emergence of new leaves down the stem.
- Urgent action is required if 5-10 out of 60 cuttings are affected and 10-15 out of 100 plants in the field.
- If you see candle appearance of stems with blackened tips the direct contol actions are too late.
- Roguing of infected plants immediately after first few rains. When carrying infected plants out of the field, do not touch healthy plants so not to infect them.
- When a bacterial blight outbreak occurs, harvest healthy root tubers and incorporate all residue deeply into the soil. Thereafter, rotate with cereals, grains or legumes for 2 seasons.
- Dust leaves with a thin layer of wheat flour which when fed on by the grasshopper, gums up its mouth part and prevents its feeding activities.
- Introduce chicken and guinea fowl to feed on disease carrying insects (12 - 24 birds/acre).
- Long grain traps: get rid of grasshoppers and other pests by growing a patch of uncut grass.
- There is no direct chemical control of cassava bacterial blight available at the moment.
CREATED/UPDATED: March 2019
PRODUCED BY: Plantwise
©CAB International. Published under a CC-BY-SA 4.0 licence.