This was a piece of advice to me from Anna McConville, who is not an ECA member, but suggested the following on this issue:

"People in Victoria have been monitoring nestboxes for quite some time (Organ Pipes National Park) and have had all sorts of problems with pests.  The only way that they have found to deal with ants is to prop open the lid which creates conditions that they don’t like. Then next time you check them, you close the lid and the cycle starts again.  They have found that the ants generally find their way back into the boxes, but may be worth trialling.  People recommend Vaseline to stop ants getting in worm farms etc and maybe a similar approach could be applied to nestboxes.  Maybe put heaps of Vaseline where the nestbox touches the tree (once the ants are gone) on a few boxes and see whether it lasts (and actually works) until the next check??"

Definately worth a try, but of course limited to sites where ready access to the boxes is possible. Makes one wonder about the effectiveness of all those nestboxes being erected for the Pacific Highway upgrades from Tea Gardens to Kempsey at the moment.

I did a wiki search to find that many tests on methoprene had been carried out, but nothing in the report referred to tadpoles? Just as a passing thought, if the rate of malaria is increasing into higher levels in certain mountainous countries, could the use of "M" be a contributing factor?  

hence the conundrum. I've still looking for some research or advice on the issue. Surprising something hasnt come up as nestboxes are widely available commercially now and have been the subject of much research since the 80's

Methoprone, sold in Bunnings is also recommended to kill Ant...particulalry Fire Ants. Is it a safe product to spread around? Could it affect (say) ant eaters? 

After years of recommending their use, I finally got a job where I could erect a decent number of nest boxes (25) specifically for the Squirrel Glider as part of a suite of ameliorative measures for a development in Port Macquarie.

Carrying a 6m extendable ladder through dense Dagger-Leaved Hakea to erect said nest boxes almost made me regret my benevolence, but I erected the boxes about 4 months ago. I recently did a spot check of 7 boxes (most readily accessible) prior to a meeting with Council on site, hoping to impress clueless engineers and desk jockeys with some cute and cuddlies they should continue to pay to be saved.

To my disappointment, I found only one had a Squirrel Glider nest in it (literally only days old) but no-one was home. I also got an Antechinus (poor substitute but its sex life is a never fail anecdote). However, what depressed me (and cause several hurried ladder dismountings followed by frenzied beating of clothes) was that all the other nest boxes were infested with several thousand very aggressive ants. Most had the entrance blocked with a resin-based material, and were happily nesting in the saw dust placed by the supplier in the bottom. I also found the sawdust to be hosting a nice nest of native cockroaches (very creepy), and holding moisture which is sure to rot the bottom out. I thorougly discourage use of sawdust in nestboxes as a result, and recommend drilling drain holes >15mm to ensure free drainage at all costs.

I am now holding off checking the rest until I can come up with a way of keeping the ants out. The obvious thought is some kind of insecticide, but a spray is out of the question due to limited longevity, potential adverse impacts on gliders, etc, and of course adverse smell which may deter occupation by the target species. Hence I will have to investigate the option of some kind of plastic bait station like the cocky baits - if they exist. I appreciate any advice on what others have done.

Last piece of advice is not to hug a nest box, or put your face too close as you open the lid, as all the boxes with ants also hosted the Australian version of the Iraqui Camel Spider - the biggest Huntsman I've ever seen. This species appears rather aggressive (ie rears up with fangs out when your hand nearly clasps it accidentally), and will not hesitate to jump over your shoulder and into the hair of the person holding the ladder while your teetering at the top.