Seasonal Flight Activity of Two <I>Homalodisca</I> Species (Homoptera: Cicadellidae) That Spread <I>Xylella fastidiosa</I> in Southern California

Abstract

Homalodisca coagulata (Say) and Homalodisca lacerta (Fowler) are vectors of a new bacterial disease of oleander in California known as oleander leaf scorch, induced by the bacterium Xylella fastidiosa. H. coagulata also has been implicated in the spread of the strain of X. fastidiosa that induces Pierce's disease of grapevines in California. We monitored the flight activity of H. coagulata and H. lacerta in oleander and citrus by using yellow sticky cards at three southern California locations where outbreaks of oleander leaf scorch have been documented, and where vector compliments are different. Areas sampled included a mesic coastal area (Irvine, CA) that supports predominantly H. coagulata and few H. lacerta, a dry inland location (Palm Desert, CA) that supports predominantly H. lacerta and few H. coagulata, and an intermediate area (Riverside, CA) supporting both Homalodisca species. From November 1996 to October 1999 peak catches of both Homalodisca species occurred during the midsummer at all locations. H. coagulata was trapped in greater numbers in citrus than in oleander at both the Riverside and the Irvine sites. Likewise, H. lacerta in Riverside was more associated with citrus than oleander, yet H. lacerta in Palm Desert was trapped in greater numbers in oleander than citrus.

Seasonal Patterns of FemaleHomalodisca coagulata(Say) (Hemiptera: Cicadellidae) Reproductive Physiology in Riverside, California

“…Timmer et al (1982) observed peak H. coagulata trap catch in June in Florida, whereas Yonce (1983) documented peaks in the number of H. coagulata in the latter part of July in South Carolina. Blua et al (2001) reported that peak adult ßight activity in Riverside, CA, occurred in July of each year from 1996 to 1999. Powers (1973) reported that the density of gravid female H. liturata increased from January to March and again from June to July, but that there was no distinct adult peak because of extensive generation overlap.…”

Feeding site preference of Dilobopterus costalimai Young and Oncometopia facialis (Signoret) (Hemiptera: Cicadellidae) on citrus plants

“…These tactics can include the use of insecticides that affect the sharpshooter vectors before they can inoculate a healthy plant or acquire the bacteria from an infected plant (Blua et al 2001). Thus, the observed sharpshooter preference for citrus sprouting has important implications for CVC management, and control measures against these insects should be adopted in periods of greater vegetation in orange orchards, which are probably critical for X. fastidiosa acquisition and transmission.…”

Identifying the predator complex of Homalodisca vitripennis (Hemiptera: Cicadellidae): a comparative study of the efficacy of an ELISA and PCR gut content assay

“…For instance, in exhaustive cross reactivity tests, the GWSS-speciWc ELISA also reacted to the egg stage (and gravid female stage) of the smoke tree sharpshooter (STSS), H. liturata ). Both the GWSS and STSS are known to co-exist in California (Blua et al 2001;Park et al 2006). Thus, predators that tested positive using ELISA could have ingested a STSS egg or gravid female instead of a GWSS egg or gravid female.…”

“…GWSS is a polyphagous herbivore, native to the southeastern and southern coastal plains of the United States. It was Wrst reported in California in 1989 (Sorenson and Gill 1996) and has since spread throughout southern California (Blua et al 2001). While feeding on the plant's xylem Xuid, it can acquire and transmit Xylella fastidiosa (Wells et al), the bacterial pathogen responsible for several devastating plant diseases such as Pierce's disease in grape, almond leaf scorch, and oleander leaf scorch (Redak et al 2004).…”