Instructions for preventing anthracnose in pepper

Anthracnose (Colletotrichum gloeosporioides) is the main cause of flower loss and young fruit loss in pepper — which can cause 20-40% yield loss. Instructions on identifying 3 plant parts, seasonal prevention and treatment regimen when first discovered.

Summary: Unlike quick death, anthracnose does not kill trees but "squeezes" underground productivity. orchards with chronic anthracnose may still be green, but the seed chains are sparse, many are flat, and the actual yield is 30-50% lower than potential. This article does not talk about general theory but focuses on 3 times when anthracnose is especially dangerous and specific ways to handle it.

Applies to: Vinh Linh pepper, Loc Ninh, Phu Quoc pepper in the Central Highlands + Southeast. Especially in areas with high rainfall of over 2000mm/year.
Duration: Room all year round. Highest pressure in May-September.
Difficulty level: Medium. Need to read the symptoms correctly + choose the right time to spray.
Estimated additional costs: 2-4 million/ha/year for periodic room.

Disease characteristics

*Colletotrichum gloeosporioides* is a multi-host fungus that causes anthracnose on mango, coffee, durian, longan, and lychee. On pepper, it attacks leaves, flowers, and young fruit chains.

Strong development conditions:

Prolonged rain + temperature 25-30°C — this is the rain in the Central Highlands + Southeast region.
Dense canopy, high humidity — densely planted orchard + no pruning.
Plant lacks potassium + lacks calcium — weak resistance.
The orchard had an epidemic last year — spores lay dormant on fallen leaves + dry branches spread again.

Unlike rapid death, anthracnose has a wider "door of rescue" — it can still be treated if detected within 1-2 weeks. But if accumulated over many seasons without control, the orchard will degrade underground.

Three dangerous times + typical symptoms

Leaves — earliest + conspicuous

In the rainy season, check the pepper leaves and see:

Round spots 5-15mm, dark brown border, light gray center with small black dots (fungal spores).
Spots develop from the edge of the leaf inwards, or from where the leaf is scratched.
Severe leaves = yellow, fall off early.

Count 30 cards on 10 pillars. If > 3 leaves have spots → anthracnose is present, priority should be given to treatment before the flowering stage.

Flowers + young string — most expensive

Pepper flowers in May-July in the Central Highlands. This is the window where anthracnose "squeezes" productivity:

Flowers are brown, dry, do not develop in chains.
Newly formed shoots are dark, dry, and fall off.
The stem of the chain is black and has rusty plastic.

Anthracnose at this stage = complete loss of productivity in that part. There is no way to "save" dead flowers — you can only stop them from spreading to another chain.

Old fruit — quality decreases

When the fruit is almost ripe:

Black/brown spots on fruit peel.
The fruit is dark, wrinkled, and flat inside.
Reduce export volume + quality.

This case mainly lost quality + selling price, not quantity.

Room — seasonal

At the end of the dry season (March-April): Cleaning + foundation spraying

Cut diseased branches, dry branches, branches touching the ground — burn away from the orchard, do not throw in the orchard.
Whitewash the base of the pillar to a height of 80-100cm.
Spray the entire orchard once with the active ingredient Mancozeb or Copper oxychloride according to the label — just in case before the rainy season.
Organic fertilizer + potassium sulfate 200-300g/head. Plants with strong internal strength = less susceptible to anthracnose.

Early rainy season (May-June): Spray before flowering

When the plant begins to flower or shows signs of bright flower buds:

Spray once with the active ingredient Azoxystrobin or Difenoconazole according to the label.
Spray in the cool afternoon, do not spray when flowers are blooming.
If the orchard has a history of severe anthracnose: repeat once every 10-14 days.

Peak rainy season (July-September): Monitoring + point processing

Check posts in low and damp areas weekly.
When you see an outbreak → immediately spray locally on the infection + 10-15 neighboring posts. No need to spray the whole orchard.
Repeat spraying after 7-10 days, change active ingredients to avoid resistance.

End of rainy season (October-November): Final cleaning

After harvest (if harvested early) or early dry season:

Clean up fallen leaves + fallen branches in the orchard.
Cut diseased branches.
Scan the base of the cylinder + spray broad spectrum once if the crop has just had an epidemic.

Many people skip this step — it happens again in the orchard, don't understand why.

Treatment when an epidemic occurs

3-step process:

1. Mark + isolate: diseased posts are marked with color, do not move fallen branches/leaves over neighboring posts. Disinfect scissors between posts.

2. Cut + destroy: remove all diseased branches/flowers/strings. Take it away from the orchard to burn. Absolutely do not throw it in the orchard — the spores will continue to spread.

3. Spraying:

Recommended active ingredients: Azoxystrobin + Difenoconazole, or Tebuconazole. Change active ingredients between sprays.
Spray evenly on both sides of leaves + stems + stems + soil around the base (spores fall to the ground).
Repeat after 7-10 days, up to 3 times.

If after 3 sprays there is no improvement → the problem may not be simple anthracnose (possibly a combination of Phytophthora and bacteria). Call a technician or local Plant Protection Department.

Monitor every 7-14 days

[ ] Count the percentage of leaves with spots on 5 representative cylinders × 30 leaves/pillar.
[ ] Observe flowers + young strings during the flowering season.
[ ] Check lower branches + inside canopy — moist area where disease accumulates.
[ ] Monitor rain + humidity — after 3-5 consecutive days of rain, prioritize checking.
[ ] Compare with neighboring orchards to predict epidemic trends.

Common mistakes

Only spray when spots are clearly visible: 5-7 days late, the disease has spread underground. Preventive spraying at the beginning of the rainy season is cheaper than spraying treatment 3 times in a row.

Spraying the same active ingredient many times in a row (eg Mancozeb for 3 years): fungus is resistant to the drug. Rotate 3-4 active ingredients with different mechanisms of action.

Abandon end-of-season cleaning: spores lie dormant on fallen leaves + dry branches → next crop blooms again.

High nitrogen fertilization to "make the plant silky": high nitrogen = soft young leaves = easy fungus invasion. Anthracnose plants should reduce nitrogen + increase potassium.

Spray in hot sun or before heavy rain: treatment evaporates or washes away, losing effectiveness.

Take notes

Every orchard should have an "anthracnose chart" by year:

Which month is strong?
The leaf/flower/fruit ratio is intermittent.
Active ingredients used + effectiveness.
Weather outbreaks.

After 2-3 years of data, you will be able to predict your own pattern, much more proactively.

References

*Prevention of pepper diseases* — Plant Protection Department, 2022.
*Export Pepper Technical Handbook* — Vietnam Pepper Association (VPA), 2023.
*Anthracnose management on citrus and industrial crops* — Plant Protection Institute, 2021.