Hong Kong Residents Warned About Lychee Stink Bugs: Risks, Prevention, and Treatment

As Hong Kong enters the peak breeding season for the lychee stink bug (Tessaratoma papillosa), residents are being cautioned about potential encounters with the insect and its defensive secretions. Although not typically dangerous, the bugs can cause discomfort and concern, particularly due to a common misconception about their toxicity. This article provides a comprehensive overview of lychee stink bugs, including their characteristics, potential risks, and effective prevention and treatment strategies.

What are Lychee Stink Bugs?

Lychee stink bugs, too known as “stinky butt bugs” due to their defensive mechanism of emitting a foul-smelling acidic liquid, are common in South China, including Hong Kong. They are particularly attracted to lychee and longan trees, feeding on the sap of flowers, young fruits, and twigs. Kingston in the Wild notes that these bugs can grow up to 24mm in length, with nymphs displaying particularly vibrant colors.

Are Lychee Stink Bugs Dangerous?

Despite local beliefs, lychee stink bugs are not poisonous and do not cause blindness. The discomfort associated with these insects stems from their defensive secretion. When threatened, they release a pungent, long-lasting odor. Contact with the acidic liquid can cause burning, stinging, redness, and swelling, but typically does not lead to ulceration.

Breeding Season and Egg Identification

The peak breeding period for lychee stink bugs is between April and July, coinciding with the flowering and fruiting stages of lychee and longan trees. Females lay 14 eggs at a time, arranged in closely packed groups of about 2-3mm in size, typically on the underside of leaves, curtains, or clothes drying outdoors. Recent reports indicate sightings in Chai Wan, though they are most commonly found in the Tai Po area.

What to Do If You Encounter a Lychee Stink Bug

Removing Eggs

If you find stink bug eggs on clothing, wear gloves or use a utensil to carefully remove them. While the eggs are not highly acidic, avoiding direct skin contact is recommended to prevent potential allergic reactions.

Eliminating Stink Bugs

Do not slap or crush the insect directly, as this will trigger the release of the defensive acidic liquid. The most effective method is to spray the bug with dilute soapy water, which will quickly kill it. This method can also be used on leaves of fruit trees to control infestations.

Treating Exposure to Acidic Liquid

If you come into contact with the acidic liquid, immediately rinse the affected area thoroughly with plenty of water or slightly alkaline water. Follow up with a general skin ointment to relieve any remaining discomfort. Severe allergic reactions are rare and would require medical attention.

Can Stink Bugs Breed Indoors?

Lychee stink bugs are primarily outdoor insects and are not well-suited to breeding indoors. They require access to fruit trees for sustenance, and reproduction. Whereas, if you have fruit trees near your home, regular spraying with soapy water can help reduce the chances of infestation. If fewer than 14 eggs are found, it likely means some have already hatched, but this is not a cause for significant concern.

Recent Incidents in Hong Kong

While stink bugs themselves are not typically life-threatening, other stinging insects have caused serious incidents in Hong Kong. In December 2024, a 63-year-old hiker died after being attacked by stinging insects in the Tai Po countryside, highlighting the importance of caution during outdoor activities. South China Morning Post reported that the hiker fell into a coma and was airlifted to the hospital, but could not be revived.

Residents should remain vigilant and take appropriate precautions when spending time outdoors, particularly in areas known to harbor stinging insects or lychee stink bugs.