Induced Defences in Tomato Plants Cause Cannibalism among Pests

Tomato plants can influence caterpillars to become cannibals, according to a study conducted by scientists from the University of Wisconsin. The results are published in Nature Ecology and Evolution.

Herbivorous pests have been known to eat each other when there is shortage of food. Some plants also influence pests by making them more predatory towards other insect species. In the study conducted by UW integrative biologist John Orrock and team, a defensive reaction in tomato plants was triggered by exposing them to methyl jasmonate (MeJA), an airborne chemical that plants release to alert others about an impending danger. When tomato plants sense meJA, they react by producing toxins that make them less nutritious to insects. Then the the tomato plants were exposed to caterpillars of a common pest, the small mottled willow moth. After eight days, the tomato plants more strongly alarmed by MeJA had lost less biomass compared with control plants or those plants that received less alarm from MeJA. This implied that the reaction was effective at protecting the tomato plants.

After two days, the researchers 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.

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