|GODFREY, KRIS - University Of California, Davis|
|ARAUJO, KARLA - University Of California, Davis|
|FOSTER, ELIZABETH - University Of California, Davis|
|Yokomi, Raymond - Ray|
|HAJERI, SUBHAS - Central California Tristeza Eradication Agency|
|DOUHAN, GREG - University Of California - Cooperative Extension Service|
Submitted to: Citrograph
Publication Type: Trade Journal
Publication Acceptance Date: 12/8/2017
Publication Date: 3/1/2018
Citation: Godfrey, K., Araujo, K., Foster, E., Polek, M., Yokomi, R.K., Hajeri, S., Douhan, G. 2018. Endemic pathogens may interfere with HLB. Citrograph. 9(2):52-55.
Interpretive Summary: Preliminary results are reported for citrus plants inoculated with multiple pathogens including the endemic pathogens Citrus tristeza virus and Spiroplasma citri and the exotic pathogen Candidatus Liberibacter asiaticus (CLas) (huanglongbing/HLB). How these pathogens interact within the tree and whether endemic pathogens will alter HLB disease development is not known. All three of these pathogens are associated with the phloem tissue of citrus hosts. Also not known is how the endemic pathogens will affect the life history, preference, or transmission ability of the insect vector of CLas, the Asian citrus psyllid (ACP), which is a phloem feeder and could potentially acquire the endemic pathogens along with CLas during feeding. At the end of one year of study, the endemic pathogens appear to interact with CLas when CLas is introduced into a plant that already harbors one or both of the endemic pathogens.
Technical Abstract: Since the first citrus tree was confirmed positive for Candidatus Liberibacter asiaticus (CLas), the causal agent of Huanglongbing (HLB) in 2012, trees continue to be found in urban areas of southern California that are also positive for CLas, demonstrating a slow spread of this disease. However, California differs from other citrus producing states that have HLB in that California citrus trees may harbor the endemic pathogens, Spiroplasma citri (Sc), the causal agent of citrus stubborn disease and/or Citrus Tristeza Virus (CTV). These 2 pathogens are associated with the phloem of the citrus tree much like CLas, and may interact with CLas when it is introduced. The nature of these interactions among these pathogens within the tree and any effect the endemic pathogens on the life history, preference, or transmission ability of the insect vector of CLas, the Asian citrus psyllid (ACP), are not known. This project was initiated to investigate these interactions. At the end of one year of study, the endemic pathogens appear to interact with CLas when CLas is introduced into a plant that already harbors one or both of the endemic pathogens. The exact nature of these interactions requires further study. The presence of Sc or CLas in a lemon, decreased ACP development time from egg to adult compared to ACP development time on a healthy lemon. In limited trials, ACP adults preferred to feed on lemons infected with Sc when given a choice of an infected lemon or a healthy lemon. This suggests that ACP adults are initially attracted to a diseased tree over that of a healthy tree.