Don't know anything about your particular mix. I do seem to recall that tobacco plants use nicotine as an insecticide, and that coffee plants do the same with cafeine. Perhaps if you soaked a few ciggeys or ground beans in the mix overnight?

My grandmother used nicotine as a insecticide. She would carry around a coffee can and chew her home grown tobacco and spit in the can. Then dilute it up and use it in the garden.

It was once sold in stores, brand name Black Flag if I recall correctly. Black Flag sold other things too I think.

There is someone over on the organic forum who will flame you sorely if you suggest nicotine as an insecticide.

This works very very well for me.2tblsp baking soda/2tblsp dish soap/2tblsp vegetable oil/32.oz cup of hot water/ mix all. add to 1 gallon of water and spray. works great for the lawn and flower beds also.

Another thing you can do is electrify your plants/soil (electroculture / electro-horticulture). Doing so activates and accelerates the plant's natural insect defenses like the release of chemical VOCs to either ward off attackers or attract predatorial insects like certain wasp species.