WIth a normal harmonic radar is this between 700 and 800 meters which is insufficient because an Asian Hornet has a range of 3 to 4 kilometers. This is why the Italian StopVespa project is not useful because after the Hornet travels more than 800 meters they have to dismantle a huge radar, put it in the trunk of the car and drive to the last position the Hornet showed up on the radar. By that time the Hornet has taken another direction and they don't find him anymore.

Absolutely not because the spin-off of Leuven University in Belgium is developing 5G radars for cars who are not bigger than a pack of cigarettes, company is called Tusk-IC. You have to be on top of the technology hype to know this!

I think sonar would be more appropriate choice than radar in this case. Sonar is cheaper, the light weight- low power realisation is easier, and its disadvantages are probably tolerable in your application.