Instructions for preventing nematodes for pepper

Knot nematodes are microscopic organisms in the soil that attack pepper roots, weakening the plant and making it more likely to die from a combination of fungal diseases. Instructions on biological and chemical prevention and treatment of severely damaged plants.

Summary: Nematodes are one of the "three great enemies" of pepper — along with *Phytophthora* (fast death) and *Fusarium* (slow death). Unlike the above two, which have clear symptoms, the nematodes burrow underground in the soil, weakening the tree over many years. orchards that do not manage nematodes have yields reduced by 20-40 percent despite good surface care. This article guides identification, prevention and treatment.

Applies to: Pepper orchards in the Central Highlands and Southeast, especially orchards that have planted trees with a history of heavy nematodes (rubber, old pepper).
Duration: Manage all year round, especially the rainy season.
Difficulty: Advanced.
Estimated additional costs: 3-6 million VND per hectare per year.

What are nematodes

Knot nematodes (*Meloidogyne incognita*, *Meloidogyne javanica*) are microscopic organisms:

Size 0.3-1 millimeter — invisible to the naked eye.
Lives in soil, moves in water or through tools.
Gets into the roots, creating nodules (small lumps) on the roots. In the nodules, female nematodes lay eggs.
Egg spores survive 3-5 years in the soil when the tree dies.

Harmful effects on pepper:

Roots form nodules — lose the function of absorbing water and nutrients.
Trees weaken — leaves turn yellow, productivity decreases.
Opens the door to other fungal pathogens — especially *Fusarium*. The combination of nematodes and *Fusarium* causes slow death disease — the number one enemy of Vietnamese pepper.

Recognize

Symptoms on plants

Productivity gradually decreases over seasons for unknown reasons.
Local yellow leaves on some branches.
Trees have poor recovery after the dry season.
The tree has a high risk of slow death disease — yellow leaves of the whole tree, roots slowly rot.

Determine for sure by digging the roots

Dig lightly 30-50 cm from the base, take a sample of hairy roots:

Strong roots: ivory white, with root hairs, evenly branched.
Roots with nematodes: blisters (small lumps the size of a grain of sand to a green pea) on the hairy roots.

A nodule is a sure sign. The orchard has 30 percent of plants with nodules, a sign of a severe epidemic.

Soil analysis

For accuracy, send soil + root samples to an agricultural laboratory:

Count the number of nematodes per 100 grams of soil.
Under 50 animals: safe.
50-200 fish: average, needs room.
Over 200 animals: heavy, needs strong handling.

Room

New orchard ready to be planted

This is the best room time:

Rotate crops for 2-3 years before planting pepper — especially land that used to grow pepper, rubber, and coffee has a history of nematodes. Recommended rotation crops: soybeans, peanuts, rice.
Soil drying during the dry season — sunlight reduces nematodes.
Lime 1.5-2 tons per hectare before planting. Lime does not kill nematodes but makes the environment difficult for them.
**Apply high doses of *Trichoderma*** before planting — antagonistic microorganisms.

The orchard is in production

Regular organic fertilization:

10-15 kilograms of organic matter per tree per year.
Supplement *Trichoderma* 200 grams per plant with organic ingredients.

Antagonistic microorganisms:

Fungi *Paecilomyces lilacinus* and *Pochonia chlamydosporia* — microorganisms that feed on nematode eggs.
Water the roots according to the label, 2-3 times per year.
Probiotics containing these microorganisms are available at agricultural centers.

Intercropping plants inhibit nematodes:

Plant *Tagetes erecta* (marigold) — roots secrete chemicals that inhibit nematodes.
Grow *Crotalaria* (sunn hemp) as a green manure crop — good for killing nematodes.

Water Management

Nematodes need moist soil to move:

Good drainage in rainy season — no localized flooding.
Water evenly, not drenched — especially in the dry season.

Treating a seriously damaged orchard

The orchard has 30-50 percent of plants with nodules

Step 1: water the biological nematode treatment base.

*Paecilomyces lilacinus* or *Pochonia chlamydosporia*.
Dosage according to label, 5-7 liters of solution per cylinder.
Repeat after 30 days.

Step 2: organic supplement + *Trichoderma*.

Fertilize 15-25 kilograms of organic matter per tree.
*Trichoderma* 300 grams per plant.

Step 3: 6-month monitoring — check the root sample again.

The orchard has over 50 percent of plants with nodules

Additional chemical treatment required:

*Carbofuran* (carbamate drug, highly toxic — needs protection): spread 30-50 grams per tree. Note: Only use when absolutely necessary. How to harvest at least 90 days.
*Ethoprophos* (organophosphate drug): similar to *Carbofuran*.
Or use *Fluensulfone* (new nematode treatment, safer but expensive).

Combining chemical + biological drugs is the most effective strategy. Use chemicals once to quickly reduce nematode density, then maintain it with biology.

The orchard is too heavy

When over 70 percent of plants have nodules + productivity is deeply reduced:

Consider digging up and replacing the orchard.
Land treated with high doses of lime + left bare for 12-24 months + legume crop rotation.
Replant pepper with a more resistant variety (Sparrow variety).

Periodic monitoring

[ ] Check root samples of 5-10 cylinders every 6 months.
[ ] Year-by-year productivity — compared to the previous year.
[ ] Percentage of trees showing signs of yellow leaves and poor productivity.
[ ] After treatment: how many percent does the number of nodules decrease?

Common mistakes

Replant pepper right on land where there was an epidemic: residual nematodes last 3-5 years. Compulsory crop rotation.

Only chemical spraying, no biological supplements: nematodes temporarily decrease, returning after 6-12 months.

Abandon organic because "only use chemical fertilizers": soil is depleted of beneficial microorganisms, nematodes grow uncontrollably.

Buying seeds from unknown sources: seedlings may be infected with nematodes from the nursery.

Do not dig to check the roots: only observe the above symptoms and cannot see nematodes.

Take notes

Results of annual soil + root analysis.
Number of nematodes per 100 grams of soil.
Percentage of plants with nodules.
Processing materials — biological, chemical, date.
Yield of each crop + rate of yellow leaves.

References

*Managing nematodes on pepper* — Plant Protection Department, 2022.
*Prevention of pepper slow death disease (nematode + fungus)* — Plant Protection Institute, 2023.
*Sustainable Pepper Technical Handbook* — Vietnam Pepper Association (abbreviated name VPA), 2022.