Prevention of yellow leaf and root rot disease in coffee

Yellow leaf and root rot in coffee is often related to soil fungi, nematodes, waterlogging and weak roots. Instructions for early identification, digging to check roots, drainage, organic improvement and treatment according to level to avoid local tree death.

Summary: Yellow leaves and root rot are a dangerous group of problems because the damaged parts are underground. Coffee trees can have yellow leaves for many months, fertilization will not turn them green, and in the dry season they will wither and die. The cause is often not just one type of fungus but a combination of: squashed soil, localized waterlogging, nematodes, root aphids, poor organic matter and damaged roots. This article guides how to diagnose by roots before treatment.

Applies to: Robusta coffee in the Central Highlands, especially replanted orchards, squashed soil, poor drainage or localized yellow trees.
Duration: Monitor all year round, handle strongly before and during the rainy season.
Difficulty level: Advanced. It is necessary to check the soil, roots and water, not just spray.
Estimated additional costs: 5-20 million VND per hectare depending on soil improvement, drainage and disease treatment.

Sign on the canopy

Plants with yellow leaves and root rot often have:

Light yellow leaves from bottom to top.
The leaves are small, thin, less shiny.
Young branches grow slowly and bud weakly.
The plant wilts quickly in the sun, even if it has just been watered or the soil is still moist.
Fruit is small, falling, light kernel.
Trees die in clusters or in low areas.

Adding more fertilizer often cannot solve the problem because the roots are damaged and the plant cannot absorb it.

Dig to check the roots

This is a required step:

Dig at the edge of the canopy, 20-40 centimeters deep.
Take both hairy roots and large and small roots to see.
Compare the diseased tree with healthy trees nearby.

Signs of root disease:

Few or almost all hairy roots.
The roots are dark brown, black, the root bark easily falls off.
Has a foul or sour smell.
The soil around the pumpkin roots is soggy or crusty.
Nematode nodules or white layer of mealybugs if present.

Distinguishing causes

Main signs	High possibility
The roots rot black, the soil stays wet for a long time	Corrosion + root rot fungus
The roots have nodules, the tree is persistently yellow	Nematodes
The roots have a white layer and many ants	Mealybugs damage roots
Acid soil, few roots, poor plant absorption	low pH + poor organic
Yellow tree after strong fertilization	Fat shock, root burn

Many orchards have 2-3 causes at the same time. Need to be treated systematically.

Conditions that cause serious illness

Prolonged rain, poor orchard drainage.
Watering too much during the dry season causes the soil to squash.
The replanted orchard did not improve the soil enough.
Perennial chemical fertilization, less organic.
Acid soil, low pH.
Weeds and residue kept moist close to the roots.
The tree bears too much fruit and recovers poorly after harvest.

Coffee roots need oxygen. Soil that stays wet for a long time weakens the roots, making it easier for soil fungi to penetrate.

Processing by level

The new tree is light yellow

Stop applying heavy chemical fertilizers.
Lightly till the root area, do not break many roots.
Supplement organic matter + antagonistic microorganisms.
Check and improve drainage.
Monitor new hairy roots after 3-4 weeks.

The tree is clearly yellow, the roots are rotten

Dig a drainage ditch if the soil stays wet for a long time.
Cut off severely rotten roots if clearly visible around the base.
Irrigate or treat the root zone with appropriate medications/products according to local instructions and product labels.
Cover with organic mulch after the soil is clear, do not mulch thickly when the roots are still wet.

Dead or nearly dead tree

Dig out diseased plants and roots.
Dry the pit and treat lime/organic waste appropriately.
Do not replant right into the diseased hole.
Check surrounding plants because the disease often spreads in clusters.

Improve water and soil

Long-term measures:

Make drainage ditches in low-lying areas.
Do not water when the root layer is still moist enough.
Organic fertilizer grown every year.
Apply lime/dolomite according to pH results, do not over-fertilize arbitrarily.
Moderate root cabinets during the dry season, clear out when the rainy season is too humid.
Avoid damaging roots when weeding or tilling the soil.

Healthy soil helps roots recover. If the soil remains squashed and acidic, the disease will return after every rainy season.

Room in the replanted orchard

Replanting orchards needs to be more careful:

Rotate crops for enough time before replanting.
Choose disease-free seedlings with untwisted roots.
Do not use potting soil from a sick orchard.
Fertilize with organic matter and microorganisms before sowing.
Monitor yellow leaves right from the first year.

If replanted trees die en masse in the first 1-2 years, the soil is often not improved enough or the seedlings are diseased.

Common mistakes

If you see yellow leaves, apply more fertilizer: the roots are damaged, the more you fertilize, the more shocked you become.

Not digging the roots: mishandling the cause.

Only use treatment without drainage: the soil is still waterlogged, the fungus continues to grow.

Replanting right into the hole of a dead tree: the new tree will encounter an old disease source.

Thick organic mulch close to roots in rainy season: retains too much moisture, increasing root rot.

Monitor and record

[ ] Location of yellow and dead trees according to plot map.
[ ] Root condition when digging.
[ ] Soil moisture and water stagnation points.
[ ] PH results or soil analysis if available.
[ ] Action taken and date of action.
[ ] Proportion of trees recovering after 30-60 days.

If the disease repeats at the same spot, review the drainage and irrigation schedule before thinking about stronger medication.