A pest which ravages the leaves of trees like the Chinese banyan leaving them bare is increasing being found on Hong Kong Island after spreading from other parts of the territory in the hot weather, an expert warned on Monday.

Larvae of the Phauda flammans moth feed on the leaves of ficus trees.

The insect was a rare sight in the SAR until around 2019 when it appeared in Tuen Mun and Yuen Long, according to Ken So, chief executive of The Conservancy Association.

Now the number of trees on Hong Kong Island affected by the pest is increasing, he said.

"For insects, because the life cycle can be shortened or the reproduction of insects can always be affected by weather conditions, particularly talking about the temperature. Higher temperatures would favour the reproduction or growth of insects. So likely, the problem of Phauda flammans is highly related to hotter weather," So said.

He said pesticides can be used to control the insect.

"Once the larvae eat the leaves with pesticides, then it will kill the larvae, so that it stops or terminates the life cycle of the insects," he said.

So added that professionals are also developing a trap specifically for Phauda flammans.