We had terrible problems with cockroaches a few years back and after a chat with a chemist friend I changed from using Borax to Boric Acid as they way to get rid of our cockroach problem.
The active ingredient seems to be the Boron that is in both Borax (Left) and Boric Acid. (Right) The main difference seems to be that Borax is a crystal and easier for the cockroaches to ignore as its large and easy to see. The Boric Acid is a powder and dissolves into the sugar/milk mixture that I use and is ingested along with the attractive sugary part of the dish and Voila - no more cockroaches!
Here's what I did...
I buy my boric acid online via eBay for about $5. As you only need a teaspoon at a time, a few hundred grams lasts a long time!
I mix 1 teaspoon of boric acid with 1 teaspoon of sugar and about a table spoon of milk in a container I can throw out.
Then I slide the lids under bins, to the back of cupboards, under the fridge - anywhere I think the cockies are hiding.
And then sit back and wait!
Yup - its that easy.
If its your first application with boric acid you will have quite a few cockroach bodies to sweep up in the next week or so. If its your second, third or more, you'll probably only get the ones that you saw which reminded you to make up some more mixture again!
If you cant lay your hands on Boric Acid, try doing this with the Borax just remember that the Borax is a bit coarser and the cockies will be able to "eat around it". I found Borax wasn't so effective as the Boric Acid once I made the change.
Green-ness: 5/5 Very green to use the minimum amounts of poison needed to deal with the infestation.
Frugal-ness: 5/5 for making it yourself!
Time cost: 2 minutes!
Skill level: Very very easy!
Fun-ness: Not so fun for the cockroaches but a blessed relief to be rid of them!