Transmission of Xylella fastidiosa to oleander by the glassywinged sharpshooter, Homalodisca coagulata

Studies were conducted to investigate the transmission of the oleander leaf scorch (OLS) pathogen to oleander (Nerium oleander L.) plants by sharpshoo ters. OLS is incited by a strain of the bacterial plant pathogen Xylella fa stidiosa Well. The glassywinged sharpshooter, Homalodisca coagulata (Say), is a principal vector of this pathogen in California. In these studies, thr ee cultivars of oleander were exposed to sharpshooters that had previously fed upon OLS-infected oleander plants. Sharpshooters were subsequently cage d on healthy oleander plants individually or in groups of three. Plants wer e observed for symptoms of disease, and ELISA was used to test for the pres ence of X. fastidiosa. The probability of infection did not differ signific antly when plants were inoculated with one insect (83 %) or with three (94 %). However, higher plant mortality rates were observed on plants inoculate d with three insects, indicating that a greater number of infection sites m ay hasten plant death. Although all oleander cultivars were equally suscept ible to inoculation by sharpshooters, 'Ruby Lace' plants were less symptoma tic and had a higher level of survival after one year than 'Hardy Pink' and 'Hardy Red'. When given a choice of the three cultivars to feed on, the nu mber of insects feeding did not differ among cultivars at 24 or 48 hours af ter exposure.