So you want to know how to get rid of cockroaches?
Well, neem oil can indeed help to get rid of cockroaches, but not as easily as you might hope...
If you landed here in the hope that neem oil makes a terrific cockroach spray, just like it makes a terrific insect spray in the garden, then I have some bad news...
The only way to kill cockroaches with neem is to get them to eat it. You'd have to make your own cockroach bait.
Let's see how you can get rid of cockroaches, with or without neem...
Cockroaches infest warm sheltered areas that offer moisture and, of course, food. Impeccable cleanliness will keep their numbers lower, but it will not get rid of roaches once they are there.
Once you have cockroaches in the household, they will not disappear by themselves. They breed fast, every cockroach capable of producing several thousand more cockroaches every year...
And since they can transmit diseases onto food causing food poisoning, and they also cause allergies (in that respect cockroaches are second only to dust mites!), let's see how we can get rid of those cockroaches.
There are two main ways of killing cockroaches. One is to kill them with a contact poison, something that will kill them if they come in touch with it. The other way to kill them is to use cockroach bait, something they eat and that poisons them.
No matter what pest you are trying to get rid off, to me bait is usually the preferred solution, if available.
Why? For one it's much easier to use. In the case of cockroach extermination you don't have to empty all the kitchen cupboards, cover all eating utensils and food so they don't get covered in poison etc.
But most importantly, you don't have to poison yourself and your environment. There are substances available that are not necessarily toxic to the environment but that kill cockroaches and other pests if ingested.
Neem is a good example.
Now you may say, "But neem isn't toxic if sprayed." That's correct...
Unfortunately neem spray is not effective on cockroaches, mostly because you can't get it on them. If you cover a roach in neem oil it will likely kill it, but as you know, those cockroaches hide in cracks and crevices and inside the walls in the most inaccessible places.
They like moisture, but moisture makes the insceticidal components in neem oil break down. It doesn't last long enough... And it doesn't repel cockroaches efficiently enough to clear your house of them. They are tough buggers.
So if you hoped spraying a bit of your neem garden spray around the house will kill the cockroaches already there and prevent new ones from moving in, sorry... It ain't as easy as that.
So why do you read in the sales information of so many neem products, "effective against cockroaches?"
Because research has shown that neem bait affects cockroaches.
Bait that was perpared with a commercial neem seed extract (neem seed extract is usally a form of neem oil, though not necessarily the raw oil) killed young cockroaches and inhibited egg laying in older cockroaches. Nymphs don't develop, the younger ones all die, some of the oldest may survive, but then they won't lay eggs.
As described on the page about neem insecticide, neem does not work as a knock down insecticide. It interferes with the insect hormones and stops them from breeding.
And regarding the repellent action of neem, well, the results for the cockroach baits are not conclusive. The scientists actually did a taste test with American cockroaches. The roaches preferred the neem treated pellets over the untreated ones! But neem treated milk cartons did indeed repel them. Go figure...
So what do you do with this information now?
Well, you don't know what exactly the scientists used, or how they prepared their bait. You could of course go and experiment, making your own bait. (If you find a great recipe that works, please share it with us!)
But I suspect for most people this sounds too hard and they won't have time to make their own bait.
So, if you want a sure fire, natural way to get rid of cockroaches, why don't you go and get yourself some boric acid?
It is easily available and non-toxic (if used properly, don't eat it!) Boric acid doesn't smell, isn't volatile, is a lot safer than cockroach gel bait, and if used correctly it works a treat.
Boric acid is strictly speaking not a bait. Cockroaches ingest it accidentally and they also absorb some through the skin.
In any way, if you want to use boric acid for cockroaches, here is an excellent fact sheet that explains in detail how it works, how to use it, including what not to do.
Neem oil is great stuff, but sometimes there are even easier solutions out there!