We always keep flour and cornmeal in the freezer. Insect eggs are often present in flour. In warm temperatures those eggs hatch and then you see them crawling about in the flour bin.
A bit of Microvaving goes a long way in your case.
When i buy a potting soil, i bake it on 100Celsius, to get read of all the bugs and weeds. microwaving is no good in this situation , as all the micro organisams and composting processes would be eliminated.
In my vegetable garden I use "companion gardening" method, garlic , basil, and marygolds, are keeping bugs away.
As far as citrus goes, a good splash of soapy water does wanders.
Unfortunately , both me and my wife are smokers, cigarete buds are good for breaking the soil, the nicotine water, strained and in a spray bottle, is a good bug deterant.
Garlic spray is just as good, Crush a few cloves (10) in a litre of water, after 3-5 days strain it troug a cloth, put it in a spray bottle.