We fresh-pack citrus and have an on-going environmental monitoring program in place. While the idea of getting a positive result can be stressful, a program will help you adjust your cleaning efforts and other processes, and prevent something worse from happening. Here are a couple of comments that might help you as you take on a program:
1.) Define what to test for, what is acceptable as a result (which may depend upon what you found, where you found it, etc). For citrus, the three pathogens most likely to cause issues are Listeria, Salmonella, and E-Coli. I don't know avocados. but I'm sure you can locate some research on them.
2.) Time your testing after cleaning, but then always have your team reclean those areas immediately after taking the tests. This gives you a clean break. Make sure that is documented in case you get a positive result.
3.) Because our log reductions occur early in the process, I focus our testing on the later part of the line/processes. Not exclusively by any means, but a majority of tests are in areas after those reductions have occurred. Those nice big log reductions mean nothing if there are bad little bugs hanging out afterwards waiting for a ride. Assume your line is similar.
4.) Focus on food contact surfaces, but also check your outer zones - floors, drains, under your A/C units, etc. A lot of issues that people have had seem to have occurred when something worked its way from outer zones inward.
If you are using the same line for both citrus and avocados, I would think that your risk assessment would be higher than if just one crop. And while citrus (not juice or juicing) has not been implicated in a recall to date (that I can locate or that anyone that we interact with is aware of), the same cannot be said of avocados. And even in citrus, it's been scientifically proven that pathogens on the peel can be transferred to the fruit when being peeled.
If you are really worried about what you might find, and don't have to start immediately for a GFSI scheme, if you have a down season (aka summer), do some testing then. That would give you a chance to react to any negative results without worrying about the cost of a recall. Not really the ideal approach, but it would give you some time to get comfortable and clean up any issues if you find them. That way when you go into a new season, you are ready and have strengthened your verification processes.
Finally, not related, but here's a good recent article about the effectiveness of different citrus packing house processes and their related log reductions that you might be useful. Comes out of Florida Citrus Research Center (Univ. of Florida): https://doi.org/10.1...fm.2018.10.014
IMO, it's better to find an issue yourself, then get a phone call from a regulatory official....