If you ever find it, please do share because I think you're mistaken. The Goa'uld withhold or threaten to withhold larvae from Jaffa they think may be disloyal, but that's not because they don't trust them with their symbiotes, it's because symbiotes are a resource that they use to bind the Jaffa to them.
Originally Posted by Peterking72
The Jaffa were genetically engineered so that their immune systems would fail at puberty. Once that happens, they need a symbiote if they are going to live. Since symbiotes mature every few years, the Jaffa need to appear loyal (or risk their lives trying to steal a symbiote from another Jaffa) if they have any hope of being given a replacement. It was a rather ingenious system of enforcing servitude until tretonin was developed.
The bit about the Goa'uld killing symbiotes and that being the cause for their lack of any population growth is from season 5:
Danny, the Goa'uld have been spreading like a plague across the galaxy for thousands of years. Now for the first time they're showing zero population growth. We're not sure why. But we intend to take advantage of the situation. We may never get a chance like this again. Are we good to go?
I know this may seem unimportant right now, but I may as well tell you anyway. I think I figured out why the Goa'uld population hasn't been growing much lately.
The first quote is from "Summit." The second is from "Last Stand." It follows Daniel observing the system lords eating a bunch of symbiotes.
The queens that were System Lords are dead, but we don't know whether all queens were high ranking or whether all high ranking queens followed their System Lords to the grave. Each System Lord needed at least one queen to produced larvae for their Jaffa and some minor Goa'uld with Jaffa armies may have had one as well (others may have been supplied the larvae by their System Lord as a way to establish fealty).
Sure, except all the Goa'uld queens are DEAD. Well at least the ones we knew of, but I don't think there are more left, unless the writers decide that one or two survived, I guess.
We know from seasons 9 and 10 that there are still plenty of lesser Goa'uld in hiding/operating along the margins (e.g. Athena, who was still alive as of the last time we saw her). That this is the case and yet, conveniently, all the queens perished when the System Lords were taken down, despite how valuable they are, seems farfetched to me. And if there's even one, they can not only make lots of symbiotes, but more queens, leading to exponential population growth.
By the way, since it's impossible to tell if someone is a queen by looking at their host, who knows if Athena was one or not. She said she was a rival to Qetesh who Ba'al referred to as his queen in "Continuum." Could this because Athena was a queen herself who tried to rise above Qetesh within the confines of Ba'al's fiefdom? I have no clue, just as I don't know how many queens might be left since I don't know how many there were to begin with.