Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 12/7/2010
Publication Date: 12/15/2010
Citation: Bextine, B., Hunter, W.B., Swatsell, C., Hail, D. 2010. Cell culture based production of Homalodisca Coagulata Virus 1 (HOCV-1): Towards a Glassy-winged Sharpshooter biological control system. 2010 Proceedings of the Pierce's Disease Research Symposium, California Food and Agriculture, December 15-17, 2010, San Diego, California. p. 9-12. Interpretive Summary: A leafhopper virus, Homalodisca Coagulata Virus 1 (HoCV-1), was shown to cause increased mortality in leafhopper cells. The glassy-winged sharpshooter, GWSS; Homalodisca vitripennis, causes crop losses in grapes known as Pierce’s disease, but also losses in fruit and nut tree crops due to the transmission of plant pathogenic bacteria. Due to insects’ rapid development of insecticide resistance, we examine naturally occurring pathogens, like insect-infecting viruses, as an additive stress to support efforts to reduce leafhopper populations. Viral biological control agents offer alternatives and supplemental measures which aid effective use of chemical controls by lowering an insects’ tolerance. The extracted virus was inoculated adult GWSS, and into GWSS cell cultures at increasing dosages to determine the maximal effect for mortality. At low doses the virus did not cause significant acute mortality in live insects, however, higher dosages did cause increased mortality. Increasing population infection with this virus may reduce the fitness of GWSS such that other control methods would be more effective.
Technical Abstract: We show that HoCV-1 can cause mortality and occurs in Texas populations of glassy-winged sharpshooter (GWSS; Homalodisca vitripennis, Hemiptera: Cicadellidae). The GWSS is an invasive pest and important vector of Xylella fastidiosa, a xylem-limited bacteria that causes Pierce’s disease in grapevine as well as other scorch-like diseases in tree fruit and nut crops. The primary method of managing the spread of Xylella is reducing GWSS populations. Methods such as chemical control are not insect specific and lead to problems such as residue contamination, injury to non-target organisms and insecticide resistance. We continue to discover new leafhopper pathogens for use as biological control agents. The HoCV-1 was extracted from populations of GWSS collected in Texas, inoculated to GWSS cell cultures, and adults. The viral extract killed all treated cell cultures within 5 days. Increase in virus titer in treated cell culture was monitored over time by virus-specific PCR. Similar results were obtained in adults which were injected. Increased HoCV infection in populations of GWSS may be one approach to making them more susceptible to currently used insecticides, or to other pathogens.