HOW TO: Prevent and kill cockroaches

With summer comes insects, and in Japan they tend to come in droves. We’ve already looked at some ways to prevent mosquitoes, but several people have asked me, “what about cockroaches?” And for good reason.

cockroach trap, baitFortunately I haven’t had to deal with cockroaches much at all during my time in Japan (happily I’ll admit, as I’m a wimp when it comes to large, icky bugs like that...). In fact, the apartment we’ve lived in the past two years hasn’t seen one cockroach.

Until last week. During the stormy weather from the typhoon.

One skittered across the kitchen floor right next to my foot. It was a small one, and my husband caught it pretty easily and tossed it off the balcony (we live on the fourth floor - but I’m skeptical that it actually died considering what they can survive). And then the next evening I noticed one slowly crawling up the wall from behind the couch. A big one. It tried to escape up the wall, but my husband made sure it met the same fate as its friend from the previous day.

I’m hoping it was just the weather that brought them inside, as I try to keep our apartment really clean, but nonetheless I found myself looking for some other ideas to prevent them from returning.

I've compiled my findings here, so read on if you too are trying to figure out how to get rid of the roaches, or if you're just curious about the ingredients used in various insecticides and other methods.

Words to know

ゴキブリ                                                   gokiburi                  cockroach
スプレー                                                   supuree                  spray
忌避                          きひ                         kihi                          avoid, evade
殺虫剤                      さっちゅうざい        sacchuuzai             insect killer/insecticide

Prevention is key

The first thing to keep in mind when it comes to cockroaches is that prevention is key. This doesn’t necessarily mean you’ll be able to prevent them completely (as you now know, in my case), but the following measures certainly can make a difference and ideally attract less of the beasts.

  • Clean regularly, especially the floors, kitchen and dishes. Vacuum up crumbs and eliminate standing water. Basically, you want to deprive them of any food/water sources.
  • Keep your trash can outside (with a lid) if possible, and empty regularly. I know this can be a bit of pain in the summer when the trash is only picked up twice a week and it smells bad. I know some people freeze their garbage until garbage day, but that probably isn’t realistic for most as freezer space is limited unless you have a large or standalone freezer, or don’t use your freezer for anything.
  • Seal up cracks or spaces insects might be able to get in. One place I’ve noticed in our apartment in our apartment is the small space between the sliding doors/windows when they are open. It’s basically a space that is just big enough for most bugs to get in. I’ll go into this more in a future post, but there are things you can attach to the frame that block this space and help prevent the bugs. (I’ve also noticed our bubble wrap on one window from winter caught at least a hundred mosquitoes. Gross.)

Cockroach baits/insecticides

Cockroach bait, as you can probably guess, is an insecticide mixed with real food ingredients such as flour, sugar, and lard, and placed in a little plastic dome or container for the cockroaches to come eat. Eventually the ingested insecticide will kill them, and if they return to their colony (before they die, of course), other roaches will eat their feces and die as well.

cockroach trap, bait, insecticide

The bait is contained within the plastic containers so it doesn’t pose much of a threat to pets or children (although if you choose to use them, you should still be careful anyway and place them in discreet places your pets or kids can’t get to, such as behind/underneath your fridge, etc.)

Main ingredients

Boric acid  -  ホウ酸
Boric acid is a naturally occurring substance and is often used in laundry and personal care products. It is generally not seen as toxic except when ingested in large amounts.

Fipronil  -  フィプロニル
Fipronil is an insecticide, highly toxic to various fish and small animals, and moderately toxic to humans. It is also a suspected carcinogen.

Hydramethylnon  -  ヒドラメチルノン
Hydramethylnon is an insecticide and highly toxic to fish and insects. I’m not sure about its effects on humans.

Some common brands (not comprehensive):
Some common brands of cockroach bait (typically in small black plastic domes or square containers) include:

ブラックキャップマルチスリム  (Black Cap Multi-slim)
ゴキブリキャップ   (Gokiburi [Cockroach] Cap)
ゴキファイター  (Goki Fighter)
コンバット  (Combat)
ゴキブリワイパア  (Gokiburi Wiper)

Another type of cockroach bait, though essentially the same as those above, is “ホウ酸ダンゴ”, or in English, “boric acid dango.”

Dango is a small dumpling, typically made of rice. So in this case, the “dango” is a dumpling made with food ingredients that entice the roaches but is also mixed with boric acid to kill them.

Cockroach traps

Another option is cockroach traps. Most are enclosed, so you won't have to clean up the remains or anything like that. These are also typically small containers, but with a sticky glue sheet at the bottom that traps the roaches when they crawl in.

cockroach trap, insecticide

For these types, you’ll want to look for ゴキブリ捕獲 (ゴキブリほかく - ほかく means “capture”), or anything with コイコイ or ホイホイ in the name.

Some common brands (not comprehensive):

コンバット  (Combat)
ネズミバスター   (Nezumi Buster) Nezumi means rats/mice but can be used for cockroaches as well.
ごきぶりホイホイ  (Gokiburi Hoihoi)
ちびっこホイホイ  (Chibikko Hoihoi)
ワイパア ゴキブリゾロゾロ  (Wiper Gokiburi Zorozoro - zorozoro essentially means “large groups”)

Insecticide sprays

If you want a spray to kill cockroaches for when you see them skittering around, you have a variety to choose from (and many of them are all-purpose). Some sprays are designed specifically to be used as a “barrier” and supposedly repel cockroaches wherever you spray (such as around doors and windows).

cockroach, insecticide

I’ve listed the common active ingredients below (they're all chemical insecticides), and as you probably can guess, you should ventilate areas where you spray insecticides with these ingredients and avoid inhaling the vapor.

Common active ingredients

pyrethroid ピレスロイド
phenothrin フェノトリン
imiprothrin イミプロトリン
resmethrin レスメトリン
phthalthrin d-T80-フタルスリン

Some common brands (not comprehensive):

ゴキジェットプロ  (Goki Jet Pro)
ゴキバリア  (Goki Barrier)  -  Puts an insecticide “barrier” around places to supposedly keep the cockroaches out.
アースジェット  (Earth Jet) - All purpose.
水性キンチョールジェット (Liquid Kinchol Jet)  - All purpose.

Non-insecticide spray alternatives

One spray that does not use harmful insecticides is ゴキブリ泡ジェット (Cockroach Foaming Jet), a foaming jet spray made with regular soap/detergent. It claims that the foam will suffocate the cockroach, thus killing it.

Another spray that does not use harmful chemicals is ムシさんバイバイ (Mushi-san Bye Bye). This is a type of “barrier spray”; so you spray the areas where you want to repel cockroaches, such as around doors, windows, behind the fridge, stove, etc. It uses a combination of essential oils as the main ingredients.

Natural methods

Of course, there are other methods that may work instead of some of the above (though I’ve yet to try them all myself).

  • Essential oils such as tea tree oil or peppermint oil supposedly repel cockroaches when sprayed around areas such as doors or windows or wherever they might get in.
  • Raw garlic cloves also supposedly repel cockroaches when left around the home (perhaps it’s the smell).
  • Vinegar, diluted with some water, can act as a repellent spray similar to essential oils.
  • Plain boric acid sprinkled in a very light layer will be picked up by the cockroaches and eaten, thus killing them. However, I don’t think this is that practical or safe in general, and certainly not if you have pets or children.
  • Regular dish soap mixed with water reportedly works as a spray to kill cockroaches.
  • I’ve also read cockroaches don’t like cedar, so may be worth getting some cedar blocks to place around your home. (Cedar also helps with moisture control).

Cockroach forecast

I stumbled upon a fun website that provides a cockroach “forecast.” The forecast is based on the weather (such as the temperature and humidity), but users can submit reports of when and how many cockroaches they have seen. You don’t need an account to submit a cockroach report. The site is Japanese-only, but is really visual so kind of fun to click around.

Gokiten or "cockroach forecast"

Over to you. What tips do you have for fighting cockroaches?

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