Coffee Leaf Rust: How to Spot It and Protect Your Coffee Trees

The good news is that resistance exists. Researchers have found local Philippine coffee varieties with resistance to the rust. If you farm coffee and other perennial crops, choosing the right variety, shade and spacing is your first defense.

How to Identify Coffee Leaf Rust

Turn a leaf over. The underside has yellow orange powdery blotches, which start as small spots of about 2 to 3 mm and grow to about 15 mm. On the upper side, the same spots show as pale yellow patches that turn brown. Many spots join, and the leaf yellows and falls. Look at the lower, older leaves first. The orange powder is the sign that tells it apart from other leaf spots that do not make powder on the underside.

• Small spots of about 2 to 3 mm appear and grow to about 15 mm.
• The underside of the leaf has yellow orange powdery blotches.
• The top of the leaf shows spots with yellow halos that turn brown.
• Badly hit leaves fall early, and shoots can die back.
• Berries stay small, and branches and trees can die in bad cases.

How Coffee Leaf Rust Hurts Your Crop

Coffee leaf rust causes wilting and defoliation that result in up to 50 percent loss in production. The Pacific Pests and Pathogens fact sheet adds that it causes defoliation, smaller berries, and branch and tree death. On high yielding trees, a heavy crop uses up the tree's reserves, so rust can cause stem dieback.

The loss depends on the variety, the weather and the shade, so your own farm may see less. Scout before the rainy season starts, so you know your risk before the leaves start falling.

How to Control Coffee Leaf Rust

1. Plant resistant or tolerant varieties. The Pacific fact sheet names Catimor as a resistant type, and Philippine researchers have found local varieties with resistance. Ask your agriculturist what is available near you.
2. Space trees so air moves through the rows, and prune so leaves dry quickly after rain.
3. Use the right shade. The fact sheet lists spacing, soil nutrition and shade as the critical cultural factors.
4. Feed the trees well, because a strong tree with enough nutrients holds its leaves and bears a heavy crop with less damage.
5. Keep the farm clean and well weeded, so leaves dry faster after rain.
6. Use clean seedlings, and follow the DA and BPI quarantine rules when you move coffee planting material.

When a Spray Makes Sense

Fungicide comes after the steps above. The Pacific fact sheet says copper is a protectant that you apply before infection, and triazoles are systemic. The same fact sheet says treatment is usually not needed above 1,700 meters. Use only products registered for coffee by the FPA and follow the label.

Keep It Out Next Season

• When you replant, choose rust resistant or tolerant coffee and clean seedlings. Arabica at low and middle elevations suffers most.
• Give light, even shade and prune every year so leaves dry quickly after rain. Heavy shade keeps leaves wet and feeds the rust.
• Feed the trees well, above all in heavy bearing years. Trees that bear heavily on poor soil drop their leaves to rust first.
• Space trees so air moves through the rows and keep the farm weeded.
• Renew old, exhausted trees by stumping. Young vigorous growth stands rust better.

Natural Enemies and Biological Help

• A white fungus (Lecanicillium) often grows over old rust spots and slows the rust. It is a friend, not a new disease.

Not Sure What You Are Seeing?

Take a clear photo of the spots or the damage up close, then the whole plant, then ask Anee, the smart farm technician in anee.io, in Tagalog or English. Anee tells you what it most likely is and what to do at the age of your crop. You can also put your scouting days on the cropping calendar, so the team knows when to walk the field.

Questions Farmers Ask About Coffee Leaf Rust