Prevention of mealybugs that damage coffee berries

Mealybugs attack coffee cherries from the young to ripe stages, causing fruit drop and reducing the quality of the kernel. Instructions for seasonal prevention, biological measures and specific drugs for fruit mealybugs in the Central Highlands.

Summary: Fruit mealybugs are different from root-damaging mealybugs — they attack directly on fruit clusters, causing young fruit to drop or fruit to not ripen evenly. Severely affected orchards reduce yield by 15-25 percent + poor kernel quality. This article focuses on early identification of flower clusters and young fruits, biological measures and correct spraying techniques.

Applies to: Robusta coffee in Dak Lak, Lam Dong, Gia Lai, Dak Nong, Kon Tum. The pressure is highest during the flowering — fruit growing period.

Duration: Track March to October.

Difficulty level: Medium.

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

Characteristics of fruit mealybugs

The aphid species that attacks coffee berries is *Planococcus citri* or *Planococcus kenyae*. Different from the original mealybug:

• Lives on the surface of the tree: clings to flower stalks, fruit stalks, between fruits in bunches.
• The body has a thick layer of white wax — protection from common crop-protection products.
• Sucking sap directly from the fruit: causes the stem to soften, the fruit to fall or not fully develop.
• Sweet nectar: entails sooty mold (black mold) covering the fruit and leaves. Fruit affected by sooty mold reduces kernel quality.

The life cycle of bedbugs is 25-40 days from egg to adult — a crop has 5-7 generations.

Early recognition

On the inflorescence

When coffee is flowering or just setting fruit:

• Look for a layer of white wax on flower stems and young fruit stems.
• Flower tips dry, do not bloom or lose petals prematurely.
• Young fruits fall early after setting 5-10 days.

On a bunch of fruit

When the fruit has developed:

• The layer of white wax in the space between the fruits in the cluster.
• The fruit is "sideways" — the aphid side does not develop.
• The stem of the cluster has viscous sap — sweet nectar secreted by aphids.
• The leaves around the bunch have sooty mold (black layer).

Count to evaluate the level

Count fruit bunches with aphids in 30 random bunches on 5 trees:

Seasonal Room

Before flowering (January-February)

• Cut diseased branches and branches that touch the ground — the path of ants' spread (aphids accompany ants).
• Whitewash the base of the tree to a height of 80-100 centimeters — ants cannot climb over it.
• Spray the foundation once with *Buprofezin* or *Pyriproxyfen* if the orchard has a history of aphids.

Flowering stage (February-April)

• Do not spray while flowers are blooming — kills pollinating insects.
• Room before flowering or after fruiting.
• Monitor weekly — if small bedbug nests are detected, treat locally.

Fruit growing stage (April-September)

This is the stage where bed bugs develop the most:

• Check every 2 weeks. Count the proportion of bunches with aphids.
• When the threshold is exceeded → spray the correct active ingredient.
• Kill the ants with the aphid spray — otherwise, the ants will bring back the young aphids.

Before harvest (October-November)

• Stop spraying 30 days before harvest — avoid residue.
• Monitor but only spray if aphids spread widely and affect fruit quality.

Biological measures

Protect natural enemies

Natural enemies of fruit mealybugs:

• Mealybug ladybug *(Cryptolaemus montrouzieri)*: specializes in eating mealybugs. Can be raised freely if purchased.
• Native ladybug: eats young aphids. Especially abundant in orchards with little spraying.
• Parasite wasp species *Anagyrus pseudococci*: lays eggs in mealybugs.
• Wolf spider at the base — not the main natural enemy but has an indirect role.

Protect natural enemies by:

• Limit broad-spectrum spraying. Prioritize selected active ingredients.
• Plant orchard plants with small flowers — basil, wild peanut, wild chrysanthemum.
• Do not hoe carefully the layer of fallen leaves under the roots — natural enemies reside here.

Kill companion ants

Ants are the key factor — without controlling ants, no amount of spraying for aphids is useless:

• Whiten the base of the trunk every quarter.
• Place ant-proof ring around the base — oil-soaked string or specialized glue.
• Destroy ant nests in the orchard — look for nests at the edge of the orchard, at the base of supporting trees.

Spray correctly

Effective active ingredients

Group of growth regulators:

• *Pyriproxyfen*: inhibits molting, highly effective with young bedbugs. Less harm to natural enemies.
• *Buprofezin*: similar, specialized for mealybugs.

Group of plant absorbents:

• *Spirotetramat*: penetrates the plant through the leaves, killing aphids in difficult-to-spray locations.
• *Acetamipride* (neonicotinoid): fast effective, risk of resistance.

Coordination:

• *Pyriproxyfen + Spirotetramat*: highly effective + low resistance.
• *Buprofezin + mineral oil*: mineral oil breaks down the protective wax layer, the drug penetrates bedbugs better.

Mineral oil — important supplement

The white wax layer protects bedbugs from drugs. Spray mineral oil (like *Petroleum spray oil*) to break down the wax layer:

• Mix mineral oil concentration of 1-1.5 percent.
• Can be mixed with main active ingredient or sprayed separately 24 hours in advance.
• Spray evenly on both sides of leaves + stems + stems.

Spray technique

• Spray in the cool afternoon.
• Spray evenly on both sides of the leaves and especially in the spaces between the fruits in the bunch.
• The tank pressure is strong enough, do not use a large nozzle to create large drops.
• Amount of water 600-1,000 liters per hectare — enough to cover the entire canopy.
• Repeat after 14-21 days, change active ingredients.

Treating heavily infected orchards

When the orchard has more than 30 percent of bunches infected with aphids:

Step 1: cut and remove the heaviest bunch of fruit — cannot be saved.

Step 2: kill ants first. Spray *Chlorpyrifos* or *Bifenthrin* at tree bases and orchard edges.

Step 3: spray combination *Pyriproxyfen + Spirotetramat + mineral oil* throughout the orchard.

Step 4: 14 days later, check. If there are still aphids, repeat with another active ingredient.

Step 5: improve the orchard — pruning branches, clearing leaves, balanced fertilization.

Follow

• [ ] Count the proportion of bunches with aphids every 14 days during the fruit growing period.
• [ ] Check the inflorescence when flowering.
• [ ] Watch for sooty mold on leaves — a sign of long-standing aphids.
• [ ] Number of natural enemies in the orchard — ladybugs, parasitic wasps.
• [ ] Ant activity — around the base, on the stem.

Common mistakes

Spraying the entire orchard even if only a few plants have aphids: wasteful + kills natural enemies.

Skip ant extermination: ants bring back young aphids within a few weeks.

Spraying the same active ingredient multiple times: aphids are resistant. Rotate 3-4 active ingredients.

Do not use mineral oil: the treatment does not penetrate the wax layer, and is less effective.

Spraying while flowers are blooming: kills pollinating bees, reduces fruit set rate.

Take notes

• Date of detection, percentage of bunches infected with aphids.
• Medications used — active ingredient, dose, date.
• Effective after 14-21 days.
• Total drug and labor costs.

References

• *Prevention of mealybugs on coffee* — Central Highlands Agricultural and Forestry Science and Technology Institute (abbreviated name WASI), 2022.
• *Integrated pest management for coffee* — Plant Protection Department, 2023.

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• Prevention of coffee root mealybugs
• Prevention of green and brown scale aphids in coffee
• Coffee stem borer prevention
• Coffee price tracking and 30-day forecast