> ## Documentation Index
> Fetch the complete documentation index at: https://badixth-dc85e378.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Diagnose and Respond to Bacterial Leaf Blight in Rice

> Identify bacterial leaf blight (BLB) from yellow wavy lesions spreading from leaf tips, and control it with resistant varieties, seed treatment, and balanced fertilization.

<Note>
  **This page does not yet carry a machine-readable `rule_card`.** An earlier revision of this note said it did. It does not, and no page in this documentation does — the `rule_card` schema exists at [Risk Model](/concepts/risk-model) and [Crop Cycle Models](/concepts/crop-cycle-models) as a definition, with no page yet conforming to it.

  So the Risk Monitoring card, the [Activity & Alerts](/guides/activity-and-alerts) bindings and the grounded response of **Ask the advisor** are **not** driven from this page. The thresholds below are written for a human reader. Treat them as the source for a rule card when one is authored, not as one.
</Note>

Bacterial leaf blight (BLB), caused by *Xanthomonas oryzae* pv. *oryzae*, spreads through irrigation water, rain splash, and wounds from wind or handling. Epidemics can wipe out large areas quickly, especially in warm, humid, and rainy conditions.

## When rice is most vulnerable

Maximum damage between tillering and heading. Severe early infection can kill seedlings (kresek phase). Wounding by wind or storm rain immediately preceding warm humid weather is the classic outbreak trigger.

## How bacterial leaf blight shows in satellite data

* **NDVI drop across whole fields** in the days after a storm followed by hot humid weather.
* Pattern often follows **water flow paths** through and between fields (irrigation channels, low spots).
* Kresek phase (early wilting) mimics submergence damage; separate with weather history and field pH.

<Warning>
  Satellite imagery cannot separate BLB from other bacterial or fungal blights. Confirm with a scout before treating.
</Warning>

## Field symptoms

* **Kresek**: whole seedlings wilt and die a few weeks after transplanting
* **Leaf blight**: yellow, wavy-margined lesions start at the leaf tip or along the margin and spread downward
* Lesions turn white to grayish as they age
* **Bacterial ooze** (milky droplets) on fresh cut ends of infected leaves in early morning - the diagnostic field test
* Whole leaves and eventually whole plants dry up

## Reduce the damage by

* **Grow resistant varieties** carrying *Xa* resistance genes.
* **Use clean, treated seed** - the disease is seed-borne. Hot water treatment or copper-based seed treatment breaks the primary cycle.
* **Balanced N** - avoid over-application; excess N sharply worsens BLB.
* **Adequate K** reduces severity.
* **Improve drainage** and avoid moving flood water from infected to clean fields.
* **Destroy infected stubble and weeds** that host the bacterium between seasons.
* **Do not walk through wet infected fields into clean ones** - the bacterium travels on clothes and equipment.

## Set an alert for early warning

<Tip>
  Turn the diagnosis into a trigger. Combine weather alerts (storms + heat) with NDVI drop alerts to flag fields at risk within days of a triggering event.
</Tip>

Recommended settings for bacterial leaf blight on rice:

* **Weather alert** - strong wind or storm event followed by daily maxima above 30 C.
* **NDVI drop alert** during tillering to heading on susceptible varieties, especially downstream of infected fields.

## Related

* [Rice Diagnosis](/guides/Crop/Rice/rice-abiotic-stress)
* [Set up automated crop alerts](/guides/alerts-notifications)