ARS | Publication request: An assessment of yellow sticky card traps as indicators of the relative abundance of adult Diaphorina citri in citrus

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 9, 2008
Publication Date: N/A

Interpretive Summary: The Asian citrus psyllid is an important, invasive insect pest of citrus that transmits citrus greening disease (huanglongbing), considered the world¿s most serious citrus disease. Disease management programs rely on disease-free nursery stock, aggressive removal of infected trees, and an intensive insect control program. The Asian citrus psyllid was first found in the USA (Florida) during 1998, and the disease was first found during 2005. The psyllid was found in Texas during 2001, but the disease has not yet been detected. Growers, researchers and regulatory personnel need tools to detect and monitor infestations of the Asian citrus psyllid. Previous research showed that yellow sticky traps have value in detecting psyllids and gauging their population trends over time. In this project, yellow sticky card traps were assessed as a tool for estimating infestation levels of adult psyllids. The value of yellow sticky traps as indicators of absolute densities of adults was found to be reduced by changes in sunlight and temperature. Captures of adults were not reduced by rain and usually only to a minor extent by wind. A positive correlation was found between captures of adults and high winds in young trees, possibly because adults in young trees are more prone to being dislodged by strong winds than those in larger trees. Significant correlations were found between numbers of adults captured on sticky traps and numbers on mature leaves. However, the research indicated that little confidence could be placed on individual predictions of adult densities on mature leaves based on trap captures. Increasing the number of traps per tree from one to three did not significantly improve individual estimates, although detection of adults in trees was improved using three traps when adult population levels were low. Yellow sticky traps deployed in citrus trees may generally be useful for detecting and gauging population trends of adults, but they are inconsistent as indicators of absolute densities.

Technical Abstract: Yellow sticky card traps were assessed as a tool for estimating infestation levels of adult Diaphorina citri, an important pest of citrus. Weekly trapping was conducted in young and mature trees with traps deployed directly in trees, one trap per tree. In addition, a comparison was made between one and three traps per tree in the mature trees. Sunlight and air temperature during the day influenced captures of adults. The value of yellow sticky traps as indicators of absolute densities of adults was therefore reduced by changes in sunlight and temperature. Captures of adults were not reduced by rain and only to a minor extent by average daily wind speed. A significant, positive correlation was found for data from the young trees between captures of adults and maximum daily wind speed, possibly because adults in young trees are more prone to being dislodged by strong winds. Significant correlations were found between numbers of adults captured on sticky traps and numbers on mature leaves. However, regression analyses indicated that little confidence could be placed on individual predictions of adult densities on mature leaves based on trap captures. Increasing the number of traps per tree from one to three did not significantly improve individual estimates, although detection of adults in trees was improved using three traps when adult population levels were low. Yellow sticky traps deployed in citrus trees may generally be useful for detecting and gauging population trends of adults, but they are inconsistent as indicators of absolute densities.