Nature is decidedly unappetizing in its discussion of how vegetables turn attackers against each other:
Integrative biologist John Orrock and his colleagues at the University of Wisconsin in Madison triggered a defensive reaction in tomato plants (Solanum lycopersicum) by exposing them to various amounts of methyl jasmonate (MeJA). This is an airborne chemical that plants release to alert each other to danger from pests. When cued with MeJA, tomato plants respond by producing toxins that make them less nutritious to insects.
The researchers then allowed caterpillars of a common pest, the small mottled willow moth (Spodoptera exigua), to attack the crop. Eight days later, they observed that plants more strongly cued with MeJA had lost less biomass compared with control plants or with ones that had received a weaker induction.
So they cued tomato plants with MeJA and then fed leaves from cued plants and non-cued control plants to single caterpillars in containers that also contained a set number of dead caterpillars. Two days later, the team observed that caterpillars fed with leaves from the treated plants had turned onto the dead larvae earlier, and had eaten more of them, than those fed with leaves from control plants.