Assessment of Triozoida limbata (Hemiptera: Triozidae) attacks: morphological and biochemical changes on Psidium guajava plants

The relationship between herbivorous insects and plants is an example of an ‘evolutionary arms race’. Understanding the relationship between insects and their host plants makes it possible to determine critical points in the bioecology of these herbivores. In this relationship, insects and plants use strategies to overcome, avoid and mitigate the actions of the other. Insect-induced galls are one of the great examples of this ‘arms race’. Psyllids (Hemiptera: Psylloidea) are among the most important gall-inducing insects. The psyllid Triozoida limbata (Triozidae) is an important pest of guava (Psidium guajava) in the Neotropics. Thus, this work aimed to determine the morphological, anatomical, and biochemical changes in guava leaves caused by T. limbata to study the ‘arms race’ between these two organisms. Therefore, the process of gall formation on guava leaves during the psyllid life cycle was described. A comparative study of the anatomy and levels of phytohormones in leaves attacked and not attacked by the psyllid was carried out. It was found that the psyllid attack triggered the plant's defence by increasing the jasmonic acid content in the leaves. The psyllid attack caused anatomical changes in the leaves (such as cell non-differentiation), allowing the insect to survive feeding on the plant. In addition, the psyllid-induced galls provided shelter for the psyllid.