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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Insects and Horticulture Research » Research » Publications at this Location » Publication #323390
Title: Transmission rates of ‘Ca. Liberibacter asiaticus’ by Asian citrus psyllid are enhanced by the presence and developmental stage of citrus flush

Author
item Hall, David
item Albrecht, Ute
item Bowman, Kim

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2016
Publication Date: 2/17/2016
Citation: Hall, D.G., Albrecht, U., Bowman, K.D. 2016. Transmission rates of ‘Ca. Liberibacter asiaticus’ by Asian citrus psyllid are enhanced by the presence and developmental stage of citrus flush. Journal of Economic Entomology. 109:558-563.

Interpretive Summary: Asiatic huanglongbing (also known as citrus greening disease) is the most devastating disease of citrus worldwide. It is caused by a bacterium that is transmitted by the Asian citrus psyllid. We recently concluded research that showed transmission rates of the bacterium are greatly increased when citrus flush is present. Flush is any new leaf growth ranging in development from first emergence up until the leaves are fully expanded yet still tender. Based on this important finding, healthy citrus should be protected from Asian citrus psyllid (ACP) infestations throughout a flush. For challenging germplasm for resistance to huanglongbing, inoculations using infected psyllids would best be achieved if flush is present.

Technical Abstract: Asian citrus psyllid (ACP) transmits a bacterium ‘Candidatus Liberibacter asiaticus’ (CLas) putatively responsible for a devastating citrus disease known as Asiatic huanglongbing (HLB) (= citrus greening disease). The psyllid and disease have invaded many citrus-growing regions around the world including the United States, where the disease is seriously jeopardizing the Florida citrus industry. Solutions are desperately being sought. We recently concluded research that showed CLas transmission rates are greatly increased when citrus flush is present. Flush is any new leaf growth ranging in development from first emergence up until the leaves are fully expanded yet still tender. In an experiment with seedlings of a rootstock cultivar ‘US-942’ (Citrus reticulata × Poncirus trifoliata), a one-week infestation of 20 ACP from an infected colony resulted in 53 to 60 percent of seedlings becoming infected when flush was present compared to only 7 percent when no flush was present. In a second experiment with ‘US-942’, 77 to 97 percent seedlings became infected when flush was present compared to 40 percent when no flush was present. A similar experiment with sweet orange (Citrus sinensis ‘Valencia’) resulted in 23, 80 and 3 percent seedlings becoming infected when young, older or no flush was present, respectively. Young plants of at least some genotypes are therefore more likely to contract huanglongbing if flush is present, with older flush promoting higher infection rates. Based on this finding, healthy citrus should be protected from ACP infestations throughout a flush. For challenging germplasm for CLas resistance, inoculations using infected ACP would best be achieved if flush is present.