|Baldwin, Elizabeth - Liz|
|RAITHORE, SMITA - Former ARS Employee|
|DETERRE, SOPHIE - Former ARS Employee|
|STANSLY, PHILIP - Southwest Florida Research And Education Center|
|TANSEY, JAMES - Southwest Florida Research And Education Center|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2017
Publication Date: 9/7/2017
Citation: Baldwin, E.A., Bai, J., Plotto, A., Manthey, J.A., Raithore, S., Deterre, S., Zhao, W., Stansly, P.A., Tansey, J.A. 2017. Effect of vector control and foliar nutrition on quality of orange juice affected by Huanglongbing (HLB): chemical analysis. HortScience. 52(8):1100-1106. doi:10.21273/hortsci.12000-17.
Interpretive Summary: Citrus greening or huanglongbing (HLB) disease is devastating Florida citrus. Efforts to control this disease includes spraying insecticides to control the insect that spreads it combined with the application of added nutrients for the trees. These practices enhance production and reduce disease symptoms for the trees. Unfortunately, the disease also results in poor fruit and juice flavor. The purpose of this study was to determine whether these practices would also mitigate the effect of the disease on fruit and juice flavor over three seasons. Results showed that there were more differences in flavor chemicals due to season than due to insecticide or nutritional treatments. Nevertheless, the treatments that included insecticide, did result in juice with higher sugars and lower acids as well as lower levels of pathogen deoxyribonucleic acid (DNA).
Technical Abstract: ‘Valencia’ orange trees from groves with 90% infection by Candidatus liberibacter asiaticus (CLas), thought to be the pathogen for citrus greening or huanglongbing (HLB) disease, were treated with insecticide (I), a nutritional spray (N), insecticide plus nutritional spray (I+N). Controls (C) were not treated. Fruit were harvested in March - April, 2013, 2014 and 2015, juiced, and the juice frozen for later chemical analyses. Titratable acidity (TA), soluble solids contents (SSC)/TA ratio, many volatiles, flavonoids and limonoids showed differences due to season, while SSC, some volatiles (ethanol, cis-3 hexenol, a-terpinene, ethyl acetate and acetone), flavonoids (narirutin, vicenin-2, diosmin, nobiletin, heptamethoxy flavone) and limonoids (nomilin and nomilinic acid glucoside) showed differences due to treatment. There was not a lot of consistency for differences among seasons. TA tended to be higher in N the first two seasons and SSC/TA higher in N or I+N for all seasons (not always significant). Bitter limonoids tended to be higher in I, N or I+N over the seasons. Principal Component Analysis showed that there was good separation by season overall and for treatment in 2013. However, in 2014 and 2015, the insecticide treatments (either I or I+N) had the highest sugar and SSC/TA levels and lowest TA levels, although not always significant, as well as higher juice CLas Ct levels, indicating lower levels of the pathogen.