Induction and suppression of herbivore-induced indirect defenses

Plants release volatiles into the air. Upon herbivory, the amounts they release from the vegetative tissues increases dramatically. Although the physiological necessity for this increased emission is not fully understood, it has interesting consequences, the most important one being that foraging predators and host-searching parasitoids use these signals to track down plants with prey. This process is referred to as "indirect defense" since these responses can augment the plant’s own "direct" defenses, such as structural barriers and toxins, when they result in decreased herbivory via increased predation. Here we will describe how plants organize indirect defenses and how herbivores have adapted to interfere with these processes.