Cockroaches: everything you never wanted to know
The insects most commonly seen in Hong Kong aren't the ones you need to worry about
No insect in the home evokes as much disgust as the cockroach, with its horror-movie looks and ability to run rapidly. They literally make us sick, spreading contamination on kitchen surfaces, plates and utensils – and on floors where babies crawl – picked up from the filth they eat and the grimy places they inhabit.
The World Health Organisation (WHO) says cockroaches are carriers of salmonella, typhoid, dysentery, cholera and many more diseases.
As if the summer humidity wasn’t enough for Hongkongers to grumble about, it provides the ideal warm, damp environment for cockroaches to thrive. May to August is the peak season for infestations in the city, says Paul Hellyer, managing director of pest-control company Rentokil Initial Hong Kong.
Watch: Hong Kong's creepy, crawly pests: tips on keeping your house insect free
That means more frequent visits by Periplaneta americana, the 4cm-long American cockroach that shelters in sewers, drains and latrines. These scavengers, says Hellyer, prefer to forage outdoors, feeding on any decaying matter, including the corpses of other insects. They stray into buildings in urban areas, especially as densely populated as Hong Kong, where there is ample sustenance.
On the plus side, Hellyer says it’s uncommon to see more than a handful of American cockroaches together. And the species pales into insignificance when compared to its smaller cousin, the German cockroach (Blattella germanica). “You’ll never see one German cockroach. You’ll see 10, 20, or thousands. If you see them, you’ve got a big problem,” he warns.
“I’ve been into restaurants where you pop the ceiling panel open and I’ve seen hundreds of thousands of cockroaches running above where people are dining and food is being prepared,” he says of the species, adding that it’s not an uncommon anecdote.
Despite its name, the German cockroach is not indigenous to Germany and is found in most parts of the world, according to the World Health Organisation (WHO). It is one of the smallest species, growing to a length of just 10-15mm.
The female usually carries an egg sac on its back that contains about 40 eggs, which hatch into larvae that mature in under two months. Over the course of a summer, what began as a small infestation could grow to a population numbering in the hundreds of thousands.
Hellyer says that because cockroaches are nocturnal, it can be difficult to determine how big the problem is. Therefore searches are usually conducted by night.
Although they will infest homes, restaurants and other food-related businesses are where they can cause major problems, he says. An unknown number of cases of food-poisoning at restaurants can be attributed to the insects, rather than substandard food, Hellyer says, adding that the food and beverages industry accounts for about 40 per cent of Rentokil’s business.
During the day, German cockroaches harbour in appliances such as dishwashers, microwave ovens, the back of fridges, or behind cracked tiles, loose mortar and holes, he says. At night, they emerge to scavenge, and they are not picky eaters. They’ll feed on a loaf of bread, a lump of left-out cheese, old food in bins or diseased scraps found on the floor.
“If there’s old chicken, burger buns and patties … that haven’t been cleaned up, it’s really hard to control them because they’ve got a proper food source. They’ll also eat any dirt or grime.”
In the home, the WHO says, they will eat book bindings, glossy paper, shoe linings, hair, and even the nails of sleeping babies and sick people.
Hellyer says even the apparently cleanest of homes and restaurants could have a hidden problem. Their presence is not necessarily a sign of bad hygiene.
“We’ve seen restaurants where there are a few hundred or a few thousand, and they’re really clean places, typically in bars and shopping malls. The problem is they share the same water source and roof spaces with other outlets. They might have pest control but their neighbours don’t do anything about it,” Hellyer says.
They also have a habit of getting everywhere.
“They are tiny little creatures which can hitch-hike and hide easily anywhere. They could be carried in with the groceries, furniture, even your travel bag. They could also get into flats through the drainage systems, piping systems and electrical and telecommunications lines. If your main door, or piping, has any gaps, they are able to enter that way as well.”
Pest-control companies tackle infestations with special organic sprays and gels that are not available to the public, after identifying the species, Hellyer says. Regular follow-up treatments are also conducted.
Surprisingly, Hellyer says cockroaches are not too difficult to get rid of in the home – especially the large American variant. Glue traps that can be bought at stores are not going to help, however. The poisonous “roach hotels”, which attract the insects with sugary substances or pheromones, “are there to help you monitor whether you have a minor or major infestation. Traps are not a total-control tool”.
The first line of defence against the pests is exclusion measures, Hellyer says, and one of the keys is good housekeeping.
“Ensure your home is as clean as possible. Clean up all food spillages and food debris,” he says, adding that it’s advisable to take the rubbish out every day. “Keep your foodstuff in closed containers, and fix any leaking pipes or taps.”
He also advises removing any old packaging materials such as carton boxes and piles of old newspaper from the house, where they may shelter and nest.
In order to prevent them getting into your property in the first place, Hellyer says: “Make sure if you have any gaps or holes or any small entry points these are sealed with cement, putty filler and other proper materials.”
If that fails, call in the exterminators.