Mango stem borer prevention

The mango stem borer causes damage due to hair clippers. The larvae burrow into the trunk and branches, causing the tree to decline, dry out the branches, and even kill the tree. Instructions for identifying holes and wood chips and treating them according to IPM for commercial mango orchards.

Summary: Mango stem borers are a group of hair clippers that lay eggs on the trunk/branches, then the larvae burrow into the wood and destroy it. Once deep inside, the spray outside the canopy is almost impossible to reach. An effective way is to detect early, clean the orchard, catch adults and directly treat the holes. This article is for Hoa Loc, Cat Chu, and Taiwanese mango orchards that are doing business.

Applies to: Hoa Loc mango, Cat chu mango, Taiwanese mango, Keo mango in the Mekong Delta, Southeast and South Central regions.
Duration: Check all year round, focusing on the beginning of the rainy season and after pruning periods.
Difficulty level: Medium. It's important to examine the trunk/branches carefully, not just the canopy.
Estimated additional costs: 1-3 million VND per hectare per year for light traps, hole treatment chemicals and orchard cleaning.

What is mango stem borer

On mango there are many species of stem-boring hair clippers, in which groups such as *Plocaederus*, *Rhytidodera* and *Batocera* are commonly found. Although the species names are different, the damage method is quite similar:

Adults lay eggs on trunk bark, main branches or wounds.
Eggs hatch into larvae.
The larvae bore through the bark, eat the soft tissue under the bark and then enter the wood.
The opaque line grows larger as the worm ages.
When mature, trim the hair to create a hole to escape.

A tree can have many larvae at the same time. If the density is high, large branches dry out or the whole tree declines quickly.

Symptoms are easy to recognize

Check the main stem, forks and level 1 branches:

There are round or oval holes in the shell.
Wood chips and worm feces extruded out.
The shell around the plastic flow hole.
The branch above the hole has yellow leaves, withered leaves, and dry branch tips.
The tree has poor buds, small leaves, and reduced productivity.

In mango, the thick canopy of branches obscures the trunk, so many orchards only detect it when the branches are dry. When you see an unusually dry branch, you have to go back down to the base of the branch to find the hole.

Why spraying chemicals is often ineffective

The larva is located in the opaque line. The bark and wood are covered so it is difficult for exposed drugs to enter. Spraying the entire canopy is only partially effective on adults or very newly hatched larvae.

Therefore, prevention must follow the direction:

Reduce spawning sites.
Catch adults before giving birth.
Detect perforations early.
Put treatment measures on the correct chisel line.

This is a pest that needs "precise manual work", not just increasing the dose of treatment.

Room before the epidemic

Cleaning and pruning branches

Cut off dry branches, diseased branches, and broken branches.
Take the cuttings out of the orchard to split or destroy.
Prune the canopy after harvest so that the trunk and main branches have light.
Do not let grass or vines cover the roots.
Apply lime or copper-based treatment to large cuts.

Haircutters like dense orchards and trees with many untreated wounds.

Wound protection

After pruning branches:

Cut firmly, do not scratch the long shell.
Cuts over 3 centimeters should be scanned for protection.
Do not cut/scrape the stem bark to force the plant to flower.
Avoid collisions when transporting fertilizer and machinery in the orchard.

Light trap and catch adults

At the beginning of the rainy season, hang light traps for 18-21 hours to catch adult hair clippers. Combine with going to the orchard early in the morning:

Observe the trunk/branch near the trap.
Catch adults perching on trees.
Record the number caught to know the peak time.

Light traps do not kill them all, but they help reduce the number of adults and warn when a closer inspection is needed.

Handling chiseled trees

New hole, few mites

Remove the wood chips from the hole.
Use soft wire to thread along the chiseled line.
If you touch the worm, kill it directly.
Stuff cotton soaked with medication approved for use according to the label into the hole.
Seal with clay/grafting wax.
Check again in 7-10 days.

If there are no new mites, the worms are dead or have been treated.

Severely damaged branches

Dried branches, long chiseled lines, peeling bark:

Remove 20-30 centimeters below the damaged area.
Split branches to look for larvae or pupae.
Destroy branches, do not pile them in the orchard.
Scan the cut to avoid fungal infection.

Keeping empty branches is usually not beneficial. It continues to be deep and easily breaks when left.

The main body has many holes

If the main stem has many holes and the tree is seriously weakened:

Assess resilience.
If the canopy is still over 60 percent healthy, treat the hole and restore the tree.
If the stem is hollow and the canopy is severely wilted, it should be cut off to avoid spreading.

If you have a long-term mango orchard, you should have a plan to gradually replace the trees, not keep the heavily damaged trees just because of regret.

Combine recovery care

After hair cutting treatment:

Apply 15-25 kilograms of organic fertilizer per mature tree.
Supplement Trichoderma around the root zone.
Irrigation keeps moisture stable.
Do not stimulate flowers immediately if the plant has just been severely damaged.
Prune the fruit if the tree is growing fruit.

Trees with perforated stems lose their blood vessels, and their ability to grow fruit is reduced. Trying to keep the yield high will cause the tree to decline further.

Monitor periodically

[ ] Check the main stem and forks every 7-10 days during the rainy season.
[ ] Remember the tree has new wood chips.
[ ] Record the number of adult hair clippers caught in light traps.
[ ] Mark the tree that has been treated with holes.
[ ] Check again after 7-10 days to see if there are still new mites.

If a plot has more than 5 percent of damaged plants, the entire plot needs to be inspected, not just the wilted plants.

Common mistakes

Only look at the leaves, don't check the stem: when the leaves wither, the worms have been there for a long time.

Spray the crop-protection product completely and skip through the hole: it cannot kill the worms inside the body.

Do not destroy damaged branches: worms continue to grow in dry branches.

After pruning branches, do not clean the cuts: creates a door for hair clipping and fungal diseases.

Encourages flowering in declining plants: plants easily lose flowers, bear fruit poorly and recover slowly.

Take notes

The tree/lot is damaged.
Position of punch hole.
Processing date.
Handling measures.
Results after 7-10 days.
Number of trees that have to have their branches cut or removed.

Taking notes helps recognize which plots have been repeated for many years, thereby reviewing whether the canopy is too dense, the trees are too old or the orchard hygiene is not good.

References

*Control of stem borers (haircutters) on mango* — Hainong technical document.
*Integrated pest management on mango* — Southern Fruit Institute.
*Instructions for preventing hair clipping on fruit trees* — National Agricultural Extension Center.