Prevention of green and brown scale aphids in coffee
Green scale aphids and brown scale aphids stick to branches, leaves, and clusters of coffee berries, suck sap and attract sooty fungi. Instructions on distinguishing from mealybugs, counting the population, protecting natural enemies, treating ants and spraying mineral oil/selective drugs when necessary.
Summary: Green scale aphids and brown scale aphids often cling permanently to branches, leaf veins and coffee berry clusters. They suck sap, causing the tree to decline, and secrete sweet nectar that causes sooty mold to coat leaves and fruits black. Severely affected orchards look black and dirty, photosynthesis is reduced, and fruit is poorly developed. This article guides how to identify, count thresholds and handle them in a way that protects natural enemies.
Applies to: Robusta coffee in the Central Highlands, especially in dense canopy orchards, many ants, few natural enemies.
Duration: Monitor from bud production to fruit cultivation, strongest in dry season and early rainy season.
Difficulty level: Medium. It is necessary to carefully examine the underside of leaves, young branches and fruit clusters.
Estimated additional costs: 1.5-4 million VND per hectare per year depending on density and number of treatments.
Distinguishing between scale and mealybugs
Scale bugs and mealybugs are both sucking insects but have different shapes:
| Features | Green/brown scale aphids | Mealybugs |
|---|---|---|
| Appearance | Flat or slightly raised like scales, green/brown | White powder, waxy like cotton |
| Location | Branch, leaf veins, fruit stem | Fruit, fruit stem, root or branch |
| Move | Stationary, little movement | Young bed bugs move more |
| Accompanying signs | Honey honey, sooty mold, ants | Honey, ants, white wax |
Green scale aphids are often harder to see on green branches because the color is similar to the branch bark. Brown scale aphids are easier to see but are often overlooked if populations are low.
Harm
- Sucking sap makes branches weak and leaves yellow.
- Fruits develop poorly if stuck on fruit clusters.
- Honey honey causes sooty mold to cover leaves black, reducing photosynthesis.
- Causing tree failure after heavy fruit bearing season.
- Create an environment for ants to grow.
In orchards with a lot of black soot, you need to look for scale or mealybugs, not just wash the fungus on the leaves.
Early recognition
On leaves
- The underside of the leaf has small dots along the veins.
- The leaves are glossy and sticky due to the sweet honey.
- Then there is a layer of black soot.
On the branch
- Young branches have small scales attached to them.
- When you gently pry, you can see the aphids stuck to the branch bark.
- Severe branches grow slowly, with few buds.
On a bunch of fruit
- Aphids cling to fruit stems and cluster stems.
- The surrounding fruit has sooty mold.
- Fruit clusters may develop unevenly.
Counting numbers
Select 10 representative trees, each test tree:
- 5 branches with young leaves.
- 5 fruit-bearing branches.
- 20 leaves on the bottom.
| Level | Action |
|---|---|
| A few small nests, many natural enemies | Monitor, do not spray |
| 5-10 percent of branches have aphids | Local treatment + ant removal |
| More than 10 percent of branches have obvious aphids or soot | Entire batch processing |
If there are many ladybugs, parasitic wasps and aphids that do not increase quickly, you should wait for further monitoring instead of spraying immediately.
Preventive measures
Prune the canopy
- Pruning dense and ineffective branches.
- Keep the orchard well-ventilated so that natural enemies can function well.
- Remove branches with severe aphids.
Ant management
Ants protect aphids to get sweet honey:
- Find the ant's way up the tree.
- Clean up ant nests around the base and edge of the plot.
- Use ant bait or locally appropriate measures.
- Do not let branches touch the ground to create ants.
Protect natural enemies
- Broad-spectrum drug restrictions.
- Keep vegetation low, with small flowers at the edge of the orchard.
- Do not spray the entire orchard when there are only a few nests.
Scale aphids are usually well controlled by natural enemies if the orchard is not continuously sprayed with strong crop-protection products.
Handling when threshold is exceeded
Small drive
- Cutting heavy branches.
- Wipe/wash easily accessible branches.
- Ant handling.
- Follow up again in 7 days.
Moderate to severe
- Spray mineral oil or a suitable product to soften the scale, following the label.
- If you need treatment, choose the right treatment for scale aphids, prioritize selection.
- Spray thoroughly the undersides of leaves, young branches, and fruit stems.
- Do not spray when the plant is lacking water or in strong sunlight.
- Comply with quarantine period if harvest is near.
The scale layer protects aphids quite well, so spraying superficially on the surface of the canopy is often less effective.
Common mistakes
Mistaking sooty mold as the main disease: sooty mold is often the result of aphids secreting honeydew.
Do not treat ants: aphids recover quickly.
Continuous broad-spectrum spraying: natural enemies reduce, aphids flare up again.
Do not spray on the underside of leaves and branches in the canopy: you will miss where aphids attach.
Wait until the branches are black with soot before treating: at that time the tree will have clearly reduced photosynthesis.
Monitor and record
- [ ] Proportion of branches with scale aphids.
- [ ] Ant status on each lot.
- [ ] Soot levels on leaves and fruits.
- [ ] Number of natural enemies observed.
- [ ] Processing date and results after 7-14 days.
Record green/brown scale aphids and mealybugs separately. These two groups are similar in harmful effects but the attachment location and spraying method are different.