Signs of disease when rice turns yellow

Yellow rice can be caused by viruses, bacteria, fungi, nematodes or physiological yellowing. Instructions for distinguishing yellow leaves due to tungro, temporary yellowing, orange yellowing, bacterial streaking, premature yellowing of leaves and root knots.

Summary: When you see golden rice, you should not rush to apply nitrogen or spray chemicals immediately. Yellow leaves can be caused by viruses, bacteria, fungi, nematodes, cold weather, nutritional deficiency or soil poisoning. Each cause is treated differently. This article helps identify the main groups of diseases when rice turns yellow to choose the right treatment.

Applies to: paddy fields showing signs of yellow leaves, yellow tips, yellow clusters or yellowing of the entire field at the stages of seedling, tillering, tillering, and flowering.

Duration: Check as soon as the field changes color; Follow up again after 3-7 days.

Difficulty level: Medium. Need to see leaves, roots, rice stages and broker worms.

Estimated additional costs: Depending on the cause; Correct diagnosis helps avoid incorrect spraying/fertilization.

The first rule when rice turns yellow

Don't deal with leaf color hastily. Four questions need to be asked:

• Does gold start from old leaves or young leaves?
• Is the gold in each cluster or the whole field?
• Are the roots healthy?
• Are there aphids, sucking insects or signs of disease on the leaves?

Adding nitrogen when the cause is unknown can make the disease worse, especially rice blast, leaf blight, brown planthopper or yellow dwarf.

Yellow leaves due to virus

Tungro

Sign:

• Dwarf tree, few buds.
• Leaf blades and leaf sheaths are shorter than normal.
• Leaves are curled or curled.
• Leaf color changes from green to orange-yellow, yellow-brown.
• Yellow starts from the tips of old leaves.
• Blooms late, flowers are small, many flat seeds.

The disease is caused by a virus, so there is no cure for infected plants. It is necessary to prevent disease transmission and remove diseased plants.

Temporary yellow disease

Sign:

• Dwarf tree.
• Yellow leaves from the tip of the lower leaf.
• There are rust-colored spots on the yellow leaves.
• Young leaves are often pale yellow.
• Early infected plants may not flower or have short flowers and flat seeds.

Yellow disease

Sign:

• The tree is a bit short, with few buds.
• Yellow to orange-yellow green leaves.
• Early infection can lead to death.
• The plant has no flowers or short flowers.
• Dark brown flat seeds.

With the virus group, the focus is on preventing brown planthoppers, green planthoppers, cotton planthoppers and other brokers.

Yellow leaves caused by bacteria

Bacterial streaks

Sign:

• Narrow, transparent streak between leaf veins.
• Brown stripes run parallel to the leaf veins.
• Severely infected varieties may turn yellow brown and die.
• The disease spreads through seeds, rain and wind.

How to prevent:

• Do not use seeds from diseased fields.
• Treat seeds before sowing.
• Stop fertilizing with nitrogen when the field is sick.
• When the risk is widespread, use crop-protection products according to local recommendations and the correct label.

Gold mosaic

Sign:

• The leaves have irregular spots.
• There are yellow stripes on the leaves.
• A heavy tree can turn the entire field orange-yellow.
• The cotton is deformed, cannot bloom, has many loose seeds.

The disease is related to insect vectors, so it is necessary to also manage vector pests.

Yellow leaves due to fungus

Yellow leaves ripen early

Sign:

• The leaves have oval yellow stripes extending to the leaf tips.
• Appears on young leaves, small leaves and old leaves.
• The tree blooms and ripens earlier than usual.
• Short cotton, flat seeds.

Usually more severe when the field is dense, moist and unbalanced with nitrogen fertilization.

Leaf sheath rot

Sign:

• Damaging fungi on leaf sheaths.
• It is heaviest when the rice is standing — making paddy fields.
• Creates long oval spots on the sheath.
• Rice leaves turn yellow.
• If the rice leaves are damaged, the rice will not bloom and the seeds will be flat.

Fungal disease groups need to clean the fields, fertilize in a balanced manner and spray fungicides at the right time if the disease is severe.

Yellow leaves due to nematodes

Nematodes attack rice roots, creating root knots:

• The roots are swollen and deformed.
• Plants cannot absorb water and nutrients.
• The leaves turn yellow and die.
• The field can be yellow in clusters.

When you suspect nematodes, you need to dig up the roots to check. If you just look at the leaves on the field surface, it is easy to mistake it for malnutrition.

Physiological yellow and weather yellow

Some cases of yellow rice are not caused by infectious diseases:

• Cold nights, lots of dew in the early mornings.
• The field lacks water.
• The roots are affected by alum, salinity, organic poisoning.
• Potassium or micronutrient deficiency.
• Water difference between high places and low places.

Signs are usually more uniform yellowing, no characteristic lesions, roots may be black or underdeveloped.

How to handle groups of causes

If you suspect a virus

• Remove diseased plants if the rate is low.
• Prevention of broker hoppers.
• Do not fertilize nitrogen to "pull the tree".
• Monitor disease spread after 3-5 days.

If bacteria are suspected

• Stop fertilizing nitrogen.
• Keep the field clear.
• Use bacterial treatment as recommended if the disease is orchid.
• Do not take seeds from diseased fields.

If you suspect fungus

• Field cleaning.
• Avoid excess nitrogen fertilization.
• Use fungicide according to label when disease is severe.
• Monitor the leaves and the flowering stage.

If nematodes or weak roots are suspected

• Dig the roots to check.
• Keep fields from drying out.
• Improve soil and clean stubble after crop.
• Only use nematode medication according to technical recommendations because some active ingredients are very toxic to humans and the environment.

Monitor periodically

• [ ] Yellow starts from old or young leaves.
• [ ] Are there any streaks, spots, edge burns or mosaics?
• [ ] Is the tree dwarfed, twisted, or unable to bloom?
• [ ] Are there any leafhoppers or insect brokers?
• [ ] Are the roots white and healthy or black, lumpy, or rotten?
• [ ] Gold in constellations or even in the whole field.

Recording all these signs will help avoid mishandling.

Common mistakes

If you see yellow, apply urea: if yellow is caused by disease or aphids, nitrogen will make the disease worse.

Fungicide spraying for viral diseases: no effect.

Do not dig up roots to check: miss nematodes, alum, organic poisoning.

Do not look at the rice stage: same yellow leaves but different causes in seedling, tillering and flowering.

Taking seeds from diseased fields: can carry disease to the next crop.

Take notes

• Date of discovery of yellow leaves.
• Rice stage.
• Location of gold in the field.
• Symptoms of leaves, roots, flowers.
• Observed broker worm.
• Treatment measures and results after 3-7 days.

If golden rice crops are repeated many times on the same field, it is necessary to check the soil, water and seeds, not just change the treatment.

References

• *Signs of disease when rice turns yellow* — Hainong technical document.
• *Integrated pest management for rice* — Plant Protection Department.
• *Rice IPM Handbook* — FAO Vietnam.

Related articles

• Instructions for preventing yellow dwarf disease — rice leaf curl stunt
• Instructions for preventing brown planthoppers from damaging rice
• Instructions for preventing rice leaf blight disease
• Rice price tracking and 30-day forecast