Oh shoot, that's actually an awesome idea. Your friend's grandma just handed out a 10,000 IQ move.
Bugs (stink bugs included) have what's colloquially called a 'Death Stench' (lol) - which tells other bugs 'Oh shit, something poisonous/dangerous is nearby, better run away'
Biologist David Rollo discovered this when studying the social behaviors of cockroaches.
When a roach locates a new amazing place full of food, it gives off a chemical pheromone to attract other cockroaches.
But when a cockroach dies, its body produces a pheremone that strongly repels the cockroaches.
They crushed dead cockroaches and spread the body-juice in different areas - some with food, some regular corners, etc. "It was amazing to find that the ockroaches avoided places treated with these extracts like the plague."
So far the research has found that the 'death stench' fatty acids are found in pretty much all common insects, and is a UNIVERSAL repellant for insects.... even woodlice and pillbugs.
Even though woodlice and pillbugs are crustacians, they produced the same set of fatty acids that create the 'death stench', and so were equally effective at repelling bugs when mashed.
They also found that a log treated with the fatty acids (extracted from dead bugs, not the mashed bug paste itself) repelled
wood beetles in an open forest environment for a full month - even through rainfall.
Bonus: Humans can't deetect the fatty acids of the 'death stench' - it's not the same compound as what sting bugs or cockroaches give off when they die.
so if you wanted to collect woodlice, pill bugs, stink bugs - any pest bugs, really, mash them up, dilute them a little so it'll fit through a spray, and hose down your plants.... I'm almost CERTAIN that it will work!
I'm honestly gobsmacked that I never made that connection. I knew about the death-chemical and how it made bugs run away, but I never made the connection "Oh, use dead bugs as a natural bug-repellant"
I.... really want to try this, now. I'm sure I could find loads of pillbugs under various rocks. The squash beetles have arrived, and something's been chewing my amaranth and peach
trees to bits.
If I could just blend up some bugs to make a universal bug-spray....if it /works/, we may have just stumbled across a solution to one of the biggest difficulties in organic
gardening: How do you stop bugs from eating your plants, without using toxic gick?
Bro, I'm so excited. Please please pleast do this and come back w the results! I'm also going to go bug-hunting when I get home.