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United States Department of Agriculture

Agricultural Research Service

Title: Time of day, seasonality, cardinal direction, and xylem sap effects on Homalodisca vitripennis population dynamics and movement in citrus

Authors
item Blackmer, Jacquelyn
item Hagler, James

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2008
Publication Date: N/A

Interpretive Summary: Host-plant quality influences insect population dynamics and the timing and extent of insect dispersal. An understanding of how these factors influence the glassy-winged sharpshooters’ development and movement is needed to better predict the spread of Pierce’s Disease and to aid management strategies. We investigated the influence of plant factors and temporal or directional components on sharpshooter population dynamics and movement in a large commercial citrus grove. Number of egg masses, nymphs, and adults were counted on branches that were sampled for xylem sap. In conjunction with xylem sap collections, sharpshooter movement was monitored with yellow and clear sticky traps during the day and overnight. Overall, 40 times more sharpshooters were trapped on yellow sticky traps than on clear sticky traps and the majority, regardless of gender or trap color, were trapped at midday. Relative to xylem sap collections, 22 amino acids were detected with proline accounting for approximately 60% of the total makeup. Most xylem traits measured, varied due to collection date and several varied with time of day, but only xylem pressure, percent amides and amide to proline ratios were positively correlated with trap catches. Egg counts varied significantly due to sampling date and cardinal direction, with the highest number of egg masses observed in early August and on the East and South sides of the trees. Adults were found in higher numbers on the South sides. Weak correlations were found between number of egg masses and essential amino acid concentrations and osmolarity in the xylem sap.

Technical Abstract: Host-plant quality influences insect population dynamics and the timing and extent of insect dispersal. An understanding of how these factors influence Homalodisca vitripennis, the glassy-winged sharpshooters’ development and movement is needed to better predict the spread of Pierce’s Disease (PD) and to aid area-wide management strategies. We investigated the influence of plant factors (i.e., xylem chemistry, osmolarity, and xylem pressure) and temporal or directional components (i.e., time of day, time of year, and cardinal direction) on sharpshooter population dynamics and movement in a large commercial citrus grove. Number of egg masses, nymphs, and adults were counted on branches that were sampled for xylem sap. In conjunction with xylem sap collections, sharpshooter movement was monitored with yellow and clear sticky traps during the day and overnight. Overall, 40 times more sharpshooters were trapped on yellow sticky traps than on clear sticky traps and the majority, regardless of gender or trap color, were trapped at midday. Relative to xylem sap collections, 22 amino acids were detected with proline accounting for approximately 60% of the total makeup regardless of time of day or collection date. Most xylem traits measured, varied due to collection date and several varied with time of day, but only xylem pressure, percent amides and amide to proline ratios were positively correlated with trap catches. Egg counts varied significantly due to sampling date and cardinal direction, with the highest number of egg masses observed in early August and on the East and South sides of the trees. Adults were found in higher numbers on the South sides. Weak correlations were found between number of egg masses and essential amino acid concentrations and osmolarity in the xylem sap.

Last Modified: 12/18/2014
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