A study on some anatomical parameters of the piercing-sucking process in leaves and branches of Pittosporum tobira L. (Pittosporaceae) infested by the cottony cushion scale, Icerya purchasi Maskell (Homoptera: Coccina, Margarodidae)

Abstract

Pittosporum tobira L. (Family Pittosporaceae) is an important plant species grown in parks and gardens in Turkey. The cottony cushion scale, Icerya purchasi Maskell (Homoptera: Coccina, Margarodidae), is an important pest of P. tobira, and causes damage mainly to the leaves, branches and stems of the host plant. In spite of the great economic importance of I. purchasi to its host plant P. tobira, information has been limited on some basic anatomical parameters of the nature of the damage to leaves and branches. The present study was, therefore, initiated to investigate the insertion and penetration of stylets into the leaves and branches of P. tobira, the length of stylets and depth of penetration in both of these tissues, and penetration of stylets into the cortex, xylem and phloem tissues and into the secretory and non-secretory canals of the leaves and branches. The results showed great variations between the leaves and branches in all the criteria observed in I. purchasi infesting P. tobira. The study found 20 whole and 23 broken mouthparts in the leaves as compared to 3 whole mouthparts and 1 broken in the branches. Length of the stylets inserted into the leaves ranged from 33.83 μm to 540.93 μm and into the branches from 202.85 μm to 340.8 μm. The stylets reached greater depths in the leaves, at 540.93 μm, as compared to 498.67 μm in the branches. The stylets in the leaves were associated with 12 secretory canals, but with none in the branches. It was found that three stylets reached xylem in the leaves as compared to one in the branches. Similarly, 17 stylets in the leaves reached to the phloem, but only 2 in the branches. No stylets were found in the cortex of the leaves, but one was found in the branches. In the leaves, 11 stylets reached and remained in the non-secretory canals, but none in the case of the branches.