Instructions for preventing nettle bugs (costa planthoppers) for pepper

The net stink bug sucks the sap from pepper leaves, causing yellow leaves and mass leaf loss. Strong attack at the young plant stage. Instructions for identification, spray thresholds and biological measures for Central Highlands orchards.

Summary: Stink bugs (also known as leafhoppers) are small insects that suck sap from pepper leaves. On young trees, nettle bugs can cause 50-70 percent leaf loss in a few weeks. Plants do not photosynthesize enough → weaken. This article focuses on early recognition and proper treatment for Central Highlands orchards.

Applies to: Pepper orchards in the Central Highlands (Dak Lak, Gia Lai, Dak Nong) and the Southeast.

Duration: Monitoring all year round, high pressure May-September.

Difficulty level: Medium.

Estimated additional costs: 1.5-3 million VND per hectare per year.

Characteristics of net stink bugs

*Diconocoris hewetti* is a common nettle bug on pepper. Features:

• Adults are 3-4 millimeters long, with characteristic net-shaped wings (this is the name).
• Lives mainly on the underside of leaves — sucks sap from young and old leaves.
• Lay eggs on leaf veins — eggs are small, hard to see.
• Life cycle 25-30 days, many generations per year.
• Strong growth in rainy season + humid temperature of 24-30 degrees Celsius.

Harmful effects:

• The top of the leaf has small yellow spots — the result of sap extraction.
• The leaves gradually turn yellow and then fall.
• Young trees are severely affected → stop growing and may die.
• Small brown-black droppings on the underside of leaves — common sign.

Recognize

Observe the leaves

• Small yellow spots on the upper surface of leaves, spreading out to become yellow areas.
• Underside of leaves: look for nettle bugs + their black droppings.
• Dried leaves + fall from the lower layer.

Check manually

• Gently smash the pepper branches on white paper in the morning.
• Fall net bugs — count them.
• Especially in areas with young branches.

Spray threshold

Count on 10 random branches at 5-10 pillars:

Seasonal Room

The beginning of the rainy season (April-May)

• Prune the canopy for ventilation — stink bugs like moist shade.
• Whitewash the roots — prevent ants (accompanying some pests).
• Spray the foundation once *Imidacloprid* if the orchard has a history.

Peak of rainy season (June-September)

This is the period when stink bugs thrive:

• Monitor weekly.
• Gently tap branches in the morning to check density.
• Spray when threshold is exceeded — do not spray on schedule.

Late rainy season (October-November)

• Spray the last round if there is still high density.
• Clean the orchard — cut fallen leaves and old yellow leaves.

Spraying

Effective active ingredients

Group of plant absorbents:

• *Imidacloprid* (neonicotinoid) — fast acting.
• *Acetamiprid* — neonicotinoid with different mechanism.
• *Thiamethoxam* — good for adult stink bugs.

Group of growth regulators:

• *Pyriproxyfen* — kills eggs and larvae. Less harm to natural enemies.
• *Buprofezin* — similar.

Coordination:

• *Imidacloprid + Pyriproxyfen* — highly effective, low resistance.

Spray technique

• Spray in the cool afternoon.
• Spray especially the underside of the leaves — stink bugs live here.
• The pressure of the bottle is strong enough to evenly cover the underside of the leaves.
• Repeat after 14-21 days, change active ingredients.

Biological measures

Protect natural enemies

Natural enemies of nettle bugs:

• Wolf spider eats young stink bugs.
• Little mantis.
• Parasite wasps lay eggs in stink bugs.

Protection:

• Limit broad-spectrum spraying.
• Plant trees on the edge of the orchard with small flowers.

Other natural enemies

Some insectivorous birds (wormbirds, warblers) eat bugs on trees. Encouraged by:

• Leave a small bush in the corner of the orchard for birds to nest.
• Do not spray too much.

Special sapling management

1-3 year old pepper plants are especially sensitive to nettle bugs:

• The young plant is not yet fully developed — each leaf is important.
• The stink bug causes defoliation → the tree stops growing for 2-3 months.
• Mature trees need to be monitored more closely.

Caring for young trees:

• Spray the room periodically with each new batch of leaves.
• Cut fallen yellow leaves — don't let them accumulate in the roots.
• Organic fertilizer + microorganisms increase plant strength.

Treating heavily infected orchards

When the orchard has more than 15 birds per branch + widespread leaf fall:

Step 1: spray immediately at the highest dose on the label.

Step 2: combine 2 active ingredients — *Imidacloprid + Pyriproxyfen*.

Step 3: spray the entire orchard, including posts without clear symptoms.

Step 4: 14 days later, check. If the density is still high, repeat with another active ingredient.

Step 5: organic fertilizer + potassium to restore weak plants after the epidemic.

Monitor every 7-14 days

• [ ] Count bugs on branches by beating them.
• [ ] Rate of leaves turning yellow and falling.
• [ ] Observe black droppings on the underside of leaves.
• [ ] Natural enemies in the orchard.

Common mistakes

Spray only the top of the leaves: bugs on the underside — no effect.

Spray according to schedule without counting: waste + kill natural enemies.

Using the same active ingredient multiple times: bugs become resistant quickly.

Ignore young trees: young trees are severely damaged → slow to develop for many years.

Canopy too dense: stink bugs like moist shade. Prune for ventilation to reduce pressure.

Take notes

• Discovery episode — date, extent.
• Active ingredient sprayed + date.
• Ratio of fallen leaves + weak trees.
• Number of natural enemies observed.

References

• *Prevention of net stink bugs on pepper* — Plant Protection Department, 2022.
• *Managing pepper pests* — Vietnam Pepper Association (abbreviated name VPA), 2023.

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