I have 2 sites with 15 trees on each site. I plan to treat all 15 trees in site 1 with a new pesticide and leave all 15 trees in site 2 untreated. The total number of bugs on each tree is measured before treatment and after treatment on both sites, even though the second site is untreated, we still measure the bugs at the same time we measure the post treated trees on site 1.
Limitation of this study is that randomly assigning trees to treatment is not possible.
I'm interested to know the effectiveness of the new pesticide. What model would be suitable to answer this research question?
Any help is appreciated!