Yes,
Don't even think about it.
99.99% chance you will bugger your pump
Pressure washer are designed to deliver a lot of water at a very high flow rate and pressure.
Sprayers are designed to deliver a tiny amount of liquid at a much higher pressure and substantial lower flow rate.
12V spray packs are not expensive and usually come with a much longer wand to keep your lungs a lot further away from what you are spraying which is usually a good idea with herbicides and even better with insecticides.
Not hard to fab up a rack to go on your ride on and power it from your battery