Settling and feeding behavior of sharpshooter vectors of Xylella fastidiosa on new plum selections apparently resistant to leaf scald disease
Plum leaf scald (PLS) is a serious disease caused by Xylella fastidiosa, which is transmitted by sharpshooters (Hemiptera: Cicadellidae: Cicadellinae). Disease management is based on planting healthy nursery trees, eradication of diseased trees and insecticides. PLS has affected the crop expansion in Brazil, but the development of plum selections that apparently are not infected under field conditions has opened new prospects to disease control based on host plant resistance. Here we investigated the morphological differences of leaves and the settling and feeding behavior of two vectors (Bucephalogonia xanthophis and Sibovia sagata) on three plum selections (SC7, SC13 and Leticia). The settling preference was evaluated by counting the number of insects landed on plants of each selection, at 24, 48 and 54 h after releasing 40 sharpshooters in a choice-test arena. Sap ingestion rates were quantified by measuring honeydew excretions of sharpshooters confined on branches of each selection for 72 h. SC7 selection was less preferred for landing, whereas SC7 and SC13 reduced sap ingestion of both vector species. Comparative light and scanning microscopy analyses indicated that SC7 and SC13 have larger epidermal cells and thick layers of epicuticular wax, which may affect stylet penetration until the xylem vessels, as well as transmission of X. fastidiosa. The results suggest that SC7 and SC13 selections show antixenosis resistance to the vectors.