A bar graph wuld be more useful then aline graph as the data are not continuous.
I agree with that, except if you want to show the various pests split out all on the one chart (the default). When using the web version of the software, I’ve found almost by accident that you can select and deselect multiple pests using the CTRL key in those grey shaded blocks, and of course by selecting date ranges you can create quite powerful heat maps for say mice and rats only, or mustelids, or possums.