Managing mealybugs and durian fruit borers according to IPM
Mealybugs and fruit borers are the two most costly pests on durian during the fruit growing stage. Instructions on identification, spray thresholds and coordination of biological — mechanical — medicinal measures for orchards in the West and Southeast.
Summary: Mealybugs and fruit borers have different attack mechanisms but both damage the commercial value of durian fruit. Good orchard rooms reduce damage to less than 5 percent. The orchard sprays chemicals continuously without a plan — still losing 15-25 percent + costs + increasing drug residue in the fruit. This article provides guidance on managing two pests according to integrated pest principles.
Applies to: Durian orchards doing business in the Southwest and Southeast. Especially orchards exported to China and Japan.
Duration: Management from fruit set to harvest — about 100-120 days.
Difficulty level: Medium.
Estimated additional costs: 4-7 million VND per hectare per crop.
Compare two objects
| Features | Mealybugs | Fruit borers |
|---|---|---|
| Species | *Planococcus*, *Pseudococcus* | *Conogethes punctiferalis* (moth caterpillar) |
| Attack location | Left stem, between spines | The inside of the fruit (perforated from the shell) |
| Symptoms | White wax layer, with sooty fungus | Small hole in the shell, sawdust pushed out |
| Harmful effects | Falling fruit, black skin, reduced price | The fruit rots inside, cannot be sold |
| Room | Easy to detect early | Hard to detect, must prevent in advance |
Managing mealybugs on fruit
Detection
Mealybugs appear on the left stem and between the fruit spines. Sign:
- Small layer of white powder on the left stem.
- Sweet honey on the stem.
- Sooty fungus (black layer) covers the fruit skin and surrounding leaves.
Count fruits with aphids among 30 random fruits:
| Proportion of fruits with aphids | Action |
|---|---|
| Less than 5 percent | Follow |
| 5-10 percent | Spray locally for bed bugs |
| Over 10 percent | Spray the whole orchard |
Room
- Cut branches that touch the ground — the path of ants (accompanied by aphids).
- Whitewash tree stumps — prevent ants from climbing.
- Destroy the ant nest in the orchard.
- Protect natural enemies — ladybugs, parasitic wasps.
Spray when needed
Selected active ingredients:
- *Pyriproxyfen* or *Buprofezin* (growth regulators) — less harmful to natural enemies.
- *Spirotetramat* — penetrates the plant through the leaves, killing aphids in difficult-to-spray locations.
- Combination of *Buprofezin + mineral oil* — wax-breaking oil, better absorption.
Spray in the cool afternoon, repeat after 14-21 days, change active ingredients.
Management of fruit borers
Life cycle and characteristics
The durian fruit borer *Conogethes punctiferalis* is the larva of a butterfly:
- Moths lay eggs on young fruit peels.
- Eggs hatch into larvae in 4-7 days.
- The larvae bore into the fruit and eat rice within 15-25 days.
- Pupates in fruit or fallen leaves at the base.
Because the worms bore inside, when you see the obvious hole, it's too late — the worms have already eaten the fruit. Must prevent in advance by protecting the fruit shell.
Room
Baking fruit — the most effective method:
- When the young fruit reaches the size of a chicken egg (45-60 days after fruit set).
- Use a mesh cloth bag or a specialized paper bag. Do not use sealed plastic.
- Cover the entire stem — butterflies can't get in and lay eggs.
- Costs 5-15 thousand VND per bag, but worth the investment for export crops.
orchard cleaning:
- Collect fallen fruit under the tree — where the caterpillars pupate. Burn or bury away from the orchard.
- Cut branches for pests and diseases — butterflies stay at night.
Pheromone trap:
- Set 5-10 traps per hectare. Trap to catch male butterflies, reduce mating rate.
- 50-70 percent effective when placed correctly.
Spraying
If you don't cover the fruit, spray it periodically:
- Phase 1: 30-40 days after fruit set — *Emamectin benzoate* or *Spinetoram*.
- Phase 2: 60-70 days after fruit set — change active ingredients.
- Phase 3: 90 days after fruit set — minimum 30 days from harvest.
Spray in the cool afternoon, evenly throughout the canopy + especially the left stem.
Coordinate management of two pests
orchards often have both pests at the same time. Coordinated management:
General calendar in the case
Small fruit set to egg-sized fruit (30-45 days):
- Watch for mealybugs appearing on the stem.
- Spray the room if the orchard has a history of aphids.
Fruit is the size of an egg to a chicken egg (45-60 days):
- Spraying for fruit borer prevention phase 1.
- Contain fruit if you have a plan.
Fruits grow large (60-90 days):
- Watch for both aphids and borers.
- Spray the correct target if detected.
30-45 days before harvest:
- Stop spraying — ensure quarantine.
- Check if the fruit envelope is intact.
When the orchard is heavily infected with both
- Prioritize treatment of mealybugs first (spreads quickly on the plant surface).
- Drug combination: *Pyriproxyfen + Spinetoram* — kills both.
- Bag the fruit immediately after spraying for a new batch of fruit.
- Cleaning the orchard — collecting fallen fruit + cutting deep branches.
Follow up every 7-10 days
- [ ] Count the proportion of fruits with mealybugs.
- [ ] Proportion of fruit with perforated holes.
- [ ] Fruit falls under the tree — what is the reason.
- [ ] How many butterflies can a pheromone trap catch?
- [ ] Number of intact fruit bags.
Common mistakes
Spraying according to an uncountable schedule: waste + create resistance + kill natural enemies.
Abandon bagging the fruit because it's "wasting effort": the cost of bagging is much lower than the damage caused by opaque fruit.
Spray the entire orchard even if only a few plants have aphids: kill natural enemies, make the epidemic worse.
Not cleaning fallen fruit under the tree: a worm nest for the next crop.
Using treatment close to harvest date: residue — cannot be exported.
Take notes
- Detection of bedbugs and worms — date, location.
- Medications used — active ingredient, dose, date.
- Coated and uncoated fruit — percentage of clean fruit when harvested.
- Total room cost.
References
- *Integrated pest management on tropical fruit trees* — Southern Fruit Institute, 2023.
- *Durian pest control* — Plant Protection Department, 2022.