Bacterial Leaf Blight Control

Symptoms

Bacterial leaf blight is caused by the bacterium Xanthomonas oryzae pv. oryzae. It starts as water soaked yellowish streaks at the leaf tips or margins that enlarge into wavy yellow to straw coloured lesions, drying the leaves from the edges inward. Milky bacterial ooze may be seen as small beads on fresh lesions in the early morning. In the seedling stage a severe form called kresek causes wilting and death of whole seedlings.

Damage

Drying of leaves reduces photosynthesis and grain filling. The kresek phase can kill young plants outright. Yield loss is usually moderate but can reach 20 to 50 percent in susceptible varieties under heavy infection, especially with high nitrogen, flooding and damage from wind, rain or insects that create entry points.

Organic & cultural control

Grow resistant varieties, which is the most reliable control. Use clean, certified seed and treat seed before sowing. Avoid excess nitrogen and split the dose. Drain the field and practise alternate wetting and drying instead of deep continuous flooding, which reduces spread. Avoid handling plants when wet. Apply Pseudomonas fluorescens as seed treatment and foliar spray. Remove infected debris and weed hosts.

Chemical control

Bacterial leaf blight is hard to cure with chemicals, so prevention and resistant varieties matter most. Where recommended, a copper based bactericide such as copper oxychloride, sometimes combined with streptocycline at the approved low rate, can slow spread when applied early. Stop top dressing nitrogen during an active outbreak. Always follow the product label dose and approval status, observe the pre-harvest interval, and consult your local KVK or agronomist before using any product.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Use resistant varieties and clean seed, avoid excess nitrogen, drain water and use alternate wetting and drying, avoid injuring plants, keep weeds down, and destroy infected residue. Avoid working in the field when foliage is wet to limit spread of the bacteria.