Prevention of dragon fruit rot

Rot of dragon fruit often breaks out after rain, after a fly sting or when the canopy is too dense, making the fruit stay moist for a long time. Instructions on distinguishing between physiological rot and fungal rot, prevention from flowering stage to post-harvest to reduce removal.

Summary: Dragon fruit rot is not a single disease. Fruit can rot due to fungi, opportunistic bacteria, fruit fly stings, prolonged rain or improper storage after harvest. The common point is that when the fruit is soft rotten, it is almost impossible to save it. This article focuses on prevention early on: keeping the canopy open, protecting young flowers and fruits, bagging fruit, harvesting when dry and carefully classifying before packing.

Applies to: White-flesh and red-flesh dragon fruit in Binh Thuan, Long An, Tien Giang, Vinh Long, Tay Ninh.
Duration: Monitor from flowering to 3-5 days after harvest.
Difficulty level: Medium. The most important things are prevention before rain and post-harvest handling.
Estimated additional costs: 3-7 million VND per hectare per crop, depending on fruit bag level and number of spraying times.

Why do fruits rot

Dragon fruit has a thin skin, lots of juice and a short time from bloom to harvest. When there is a small wound, fungi and bacteria can easily penetrate:

Prolonged rain makes the fruit skin wet for a long time, causing microorganisms to thrive.
Fruit fly sting opens the way to rot from the inside.
Rubbing marks when applied too thickly cause scratches on the fruit's skin.
Anthracnose, black spots on fruit can turn into rot when exposed to moisture.
Harvest while the fruit is still wet accelerates rot after packing.

Therefore, fruit rot prevention must start from the orchard, not just after picking.

Distinguishing types of rot

Soft rot is caused by moisture and opportunistic bacteria

The rot is soft and watery.
Slight sour or foul smell.
Spreads quickly after 1-2 days if the fruit is tightly packed and hot.

Commonly occurs after long rains or when harvesting — transporting in humid conditions.

Rotten from fly sting

There are small dots on the outside of the shell, a bit soft around the dots.
It turned out that the meat was mushy, with maggots or sugar inside.
Fruit can rot before the skin changes color clearly.

If there are many of these types, fruit flies must be treated in parallel.

Fungal rot on the shell

The rot has clear borders, initially brown or black spots.
Later it sinks down, spreads, and can crack the shell.
Often appears with anthracnose, black spots or after mechanical injury.

Post-harvest rot

It still looks beautiful when cut, but 1-3 days later it becomes soft and watery.
It often happens when fruit is harvested wet, not sorted carefully, or packed too tightly.

Conditions that cause disease outbreaks

Fruit rot increases sharply when:

The rain lasts for 2-3 days right when the fruit is large or nearly ripe.
The orchard is dense, the fruit is deep in the canopy, it is difficult to dry after rain.
The grass is tall, the fruit has fallen and there are still many disease residues.
High nitrogen fertilization makes fruit skin soft.
Harvesting and transporting causes the left ear to be crushed or the shell to be scratched.

Red flesh is often more sensitive than white flesh to poor moisture management, especially in the Mekong Delta.

Staged Room

Before flowering

Prune branches within the canopy, keeping posts clear.
Clean up dry branches, leftover fruit, and debris under the tree.
Balanced fertilization, limit high nitrogen before the rainy season.
Add potassium, calcium — boron to make the fruit skin stronger.

Goal: reduce the source of fungus and help future fruit have healthy skin.

Flower blooming stage

Do not spray rain on the canopy when the flowers are blooming.
Monitor after the rain, especially if the flowers have dark spots or fall off abnormally.
Spray to prevent fungus before prolonged rain if the orchard has a history of fruit rot.

Slightly infected flowers can produce weak fruits that can easily rot in later stages.

Young to large fruit

Prune deformed fruit, spotted fruit, fruit located too deep in the canopy.
Bag the fruit for beautiful batches or batches that are often bitten by flies.
Check for fly stings and disease spots every week.
Spray to prevent fungus after heavy rain if the orchard has high pressure, rotating active ingredient groups according to the label.

Do not spray when it is about to rain. After spraying, heavy rain within a few hours often reduces effectiveness.

Nearly harvest

Stop taking the treatment at the right time of isolation.
Harvest when it's dry, best in the morning after the dew has dried.
Do not cut fruit immediately after rain if you can wait a day for the peel to dry.
Discard fruit with spots, softness, stings or crushed ears.

Handling when there is rotten fruit in the orchard

If the rot is scattered

Cut off diseased fruit and take it out of the orchard.
Check neighboring fruit because the disease often spreads in clusters.
Increase ventilation around the diseased column.
Follow up again in 3-5 days.

If rot spreads quickly after rain

Collect all rotten and fallen fruit.
Prune away thick branches and branches that touch the ground.
Spray the entire orchard to prevent fungus with the right active ingredient, on the right label, to avoid constant overlap.
Check for fruit flies because their sting often leads to rot.

If there is a lot of post-harvest rot

Check the cutting time: do you cut when the fruit is wet?
Check the packing operation: are there any crushed ears or compression too tight?
Increase the sorting step before packing.
Cool and ventilate the shipment before long-distance transportation.

Post-harvest management

Post-harvest rot determines the reputation of the shipment:

Use clean, sharp scissors; Do not jerk left with your hand.
Place the fruit lightly, do not pour it from a large bag onto the floor.
The fruit has stings, sunken spots, and soft areas.
Let the fruit dry and air before closing.
Do not close wet or hot fruit in the sun.

If selling to traders traveling far away, you should clearly state which batches were cut after the rain, which batches were covered with fruit, and which batches had high disease pressure to classify prices and routes accordingly.

Common mistakes

Only use treatment when the fruit is soft and rotten: the rotten fruit cannot recover. treatment only protects the healthy part.

For dense canopy during the rainy season: fruit takes a long time to dry, fruit rot and anthracnose increase at the same time.

Do not treat fruit flies: fly stings are the entrance to fruit rot.

Harvested right after the rain: wet fruit, soft skin, easy to rot after closing.

Packing the box too tightly: heat and moisture accumulate, rot spreads quickly during transportation.

Monitor and record

[ ] Rate of rotten fruits per 100 fruits tested per lot.
[ ] Number of rainy days before disease outbreak.
[ ] Rot location: on the tree, under the root, after harvest.
[ ] Percentage of fruit with fly stings.
[ ] Date of room spraying, active ingredients, quarantine period.
[ ] Reject rate when packing.

Record orchard rot and post-harvest rot separately. These two groups have different causes, if combined it will be difficult to correct the process.