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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #312588


Location: Subtropical Plant Pathology Research

Title: Within-orchard edge effects of the azimuth of the sun on Diaphorina citri adults in mature orchards

item ANCO, DAN - North Carolina State University
item Gottwald, Timothy

Submitted to: Journal of Citrus Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2014
Publication Date: 1/1/2015
Citation: Anco, D.J., Gottwald, T.R. 2015. Within-orchard edge effects of the azimuth of the sun on Diaphorina citri adults in mature orchards. Journal of Citrus Pathology. 2(1):1-9.

Interpretive Summary: Asian citrus psyllids (ACP) are attracted to light. Studies were conducted to see if ACP localize in different areas of a grove in relation to time-of-day and time-of-year, since the angle of incoming sunlight changes according to those factors. More ACP were observed during summer sampling periods, but substantial changes in their localization within groves in relation to time was not observed. Results are beneficial in the sense that ACP scouting protocols and management methods do not need to be spatially adapted within groves depending upon the time-of-day or time-of-year of their employment.

Technical Abstract: Huanglongbing (HLB) has been considered the most devastating disease of citrus. The bacterium and vector associated with HLB in Florida are ‘Candidatus Liberibacter asiaticus’ and Diaphorina citri (Asian citrus psyllid), respectively. D. citri is positively phototropic, and higher populations have been found along edges of orchards exposed to the sun. An experiment was designed to determine if D. citri adult populations along edges of orchards varied according to time-of-day and time-of-year in relation to the azimuth of the sun. The experiment was conducted twice. Citrus orchards, each divided into nine sampling areas, were surveyed for D. citri via stem-tap sampling. Orchards were sampled three times per day (near sunrise, solar noon, and sunset) and four times per year (near the summer solstice, autumnal equinox, winter solstice, and vernal equinox). Time-of-year and sampling area significantly affected psyllid counts (P = 0.0518 and 0.0630, respectively). D. citri adults were most prevalent during the summer solstice sampling period. No overall significant time-of-day effect was observed (P > 0.6). Localization of adult D. citri in sampled citrus orchards did not significantly change in relation to time-of-year (P = 0.0907). Linear mixed regression was used to fit a quadratic equation to log D. citri abundance data in relation to elevation-corrected azimuth at the time of sampling; the fitted model was significant and predicted log D. citri abundance to exhibit a concave-up pattern with increasing elevation-corrected azimuth.