Alterations of foliar arthropod communities in a maize agroecosystem induced by the root-associated fungus Trichoderma harzianum

Plants establish multitrophic interactions above- and belowground with arthropods and microorganisms. Trichoderma spp. are common soil fungi that colonize roots and promote plant growth and health. Under controlled conditions, Trichoderma spp. have been shown to induce plant resistance against the attack of foliar herbivore insects. Here, we investigated the effect of field inoculation with Trichoderma harzianum in the rhizosphere of maize plants during the vegetative plant growth phase on the community of pest and beneficial arthropods associated with maize foliage. Independent of T. harzianum inoculation, the arthropod community was complex and harbored chewing and piercing-sucking herbivores as well as natural enemies. Inoculation with T. harzianum increased the abundance of chewing herbivores, decreased the number of piercing-sucking herbivores and increased the abundance of sampled pest regulating arthropods. In addition, we provide a biochemical basis of shoot metabolites, which may be involved in the alterations of the foliage arthropod community mediated by T. harzianum. Inoculation with T. harzianum caused substantial changes in the levels of sucrose, jasmonic acid (an activator of defense responses against herbivory) and (Z)-3-hexen-1-ol (a volatile compound that attracts natural enemies of herbivores). In conclusion, our results show that inoculation with T. harzianum can alter the arthropod community associated with maize foliage and reduce the abundance of specific pest insects under field conditions.