Botox-like muscle relaxant peptides [link] (they have them in bulk at alibaba.com) could be insecticides, possibly relaxing the muscles at insect mouthparts or causing GI tract smooth muscle not to move, killing, starving, or removing motional transport (slackening limbs) at the insect. It might also
be possible to block reproduction with muscle relaxant peptides.
As peptides these short amino acid sequences could be genetically engineered into crops or genetically engineered into mycorhizzial community bacteria or fungi to kill wormlike pests while producing minimal above-ground chemical or peptide concentrations.
Also, possible application to silviculture and arborculture as well as agriculture with trees producing muscle relaxant peptides at bark and sap.
A nifty possibility is that insect muscle relaxant peptides might be completely different from mammal/human peptides making this even safer.