GLASSY-WINGED SHARPSHOOTER IMPACT ON WASHINGTON NAVEL ORANGE YIELD, FRUIT SIZE, AND QUALITY

• Author(s): Hix, Raymond; Arpaia, Mary; Grafton-Cardwell, Elizabeth; Lovatt, Carol; Phillip, Phil;
• Abstract: Prior to this study, it was unknown what impact the glassy-winged sharpshooter (GWSS), Homalodisca coagulata, had on fruit yield, fruit size, and quality as well as tree vigor. The effects of the high feeding populations of GWSS on navel orange peel nutrient status and metabolism have been consistent for the four years of the study. High GWSS feeding populations significantly reduced peel Ca and Mg concentrations all years of the study: year 1 (P=0.05) and year 2 compared to the low GWSS population (P=0.001). High GWSS feeding populations significantly disrupted N metabolism causing high peel nitrate-N or total N in years 1 and 2, respectively (P=0.05). High GWSS feeding populations significantly increased peel arginine and putrescine concentrations in four years of the study with the magnitude of the difference between the two treatments greater in years 2 and 3 (P=0.05). High GWSS feeding populations resulted in a numerically higher concentration of proline in year 1 and a significantly higher proline concentration in year 2 (P=0.05). Although GWSS feeding causes changes in peel Ca, Mg and N status, high levels of feeding and the induced changes occur after maximum peel thickness and, thus far, have not affected external fruit quality. The changes in metabolism induced by GWSS feeding are indicative of tree stress. The increased magnitude and statistical significance of these metabolic changes over the first two years of high GWSS feeding pressure is consistent with cumulative stress to the trees. High feeding pressure resulted in significant yield losses in Washington navel oranges.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium