Histology of the damage in fruits and branches of ‘Hass’ avocado trees caused by armored scales (Hemiptera: Diaspididae)

Abstract

Armored scales Abgrallaspis aguacatae and Hemiberlesia lataniae are occasional pests of 'Hass' avocado trees; however, they can cause problems during the production and packing of the fruit. Despite its importance as pests, the interactions between these insects and their host plants has been little studied. The aim of this study was to determine if armored scale species cause histological alterations in fruits and branches of 'Hass' avocado trees. Physiologically mature fruits and young branches with and without the presence of armoredscaleswerecollectedinfivecommercialorchardsof Michoacán, Mexico, in January and July 2011. Histological sections were performed in order to observe changes that occurred at the cellular level in response to the presence of the scales. Three species were identif ied: Hemiberlesia lataniae, Hemiberlesia dif f inis and Abgrallaspis aguacatae. These scales caused no macroscopic or anatomical changes in the tissues of branches and fruits, but the accumulation of phenols was detected, in response to the presence and the feed process of these species, in interior cell walls of epidermis and bark cells, as well as on the walls and cytoplasm of epidermal and parenchymal tissues of the exocarp, and in the area where the insects were located. In the branches, the stylets of the scales were found in the bark and fruits, and most were located in the exocarp cells. Apparently, the mouthparts of the scales penetrated the tissues of avocado intracellularly, and no association of the stylets with the vascular tissue was observed.