The phrase "infested areas" refers to places that are overrun or filled with a large number of unwanted organisms, such as pests or parasites. Full definition
Based on experiments in infested areas of Georgia and subsequent biogeochemical modeling, Hickman's team found that the end result of these microbial communities springing up is an average 127 % increase in soil nitric oxide (NO) emissions in invaded areas. (blogs.nature.com)
Also, some users in heavily infested areas found the collar alone were not enough to control fleas and ticks and they needed to treat the home and yard too. (petsprinciple.com)
It works incredibly well though, and this is the one I use when I'm going to be in the woods or in tick infested areas. (wellnessmama.com)