How to stop my dog's aggression towards strangers on our property?

Hello, and thanks for your question. It sounds like Tikka knows where "her" property is, and is feeling the need to protect it from strangers. This definitely needs to be addressed, as it can easily escalate to a bite if Tikka feels threatened by your visitors. Even though she's used to the men in your family, that doesn't necessarily extend to an understanding that "men in general" are ok - she knows who is in her family and who is not. She doesn't know that the visitors are your welcomed guests - she sees them as intruders and threats.

You need to set up a boundary to protect your visitors and keep Tikka separated from them until she relaxes and realizes they are not a threat - and I highly recommend working with a trainer or veterinary behaviorist on this behavior. Some dogs who feel very protective are never able to relax and be trusted with strangers - in which case they just need to be kept separate for the duration of the visit. She may need a fence (or invisible fence) to keep her from approaching visitors as they arrive, and/or you may need to put her in another part of the house whenever you are expecting people. This is both to protect your visitors, AND to protect Tikka and help her by removing her from an interaction that is causing her stress.

Your vet should be able to direct you to a veterinary behaviorist or reputable trainer in your area, and I would touch base with them immediately. This behavior should be addressed as early as possible.

I hope this helps!