Performance of 'Valencia' orange (Citrus sinensis [L.] Osbeck) on 17 rootstocks in a trial severely affected by huanglongbing

- In a sweet orange field trial, large differences were noted between rootstocks.
- Highest yields in the trial were on US-942 and US-1516 hybrid rootstocks.
- It was estimated that huanglongbing disease resulted in a 33% yield reduction.

'Valencia' orange (Citrus sinensis [L.] Osbeck) was grown on 17 rootstocks through seven years of age and the first four harvest seasons in a central Florida field trial severely affected by huanglongbing (HLB) disease. All trees in the trial had HLB symptoms and were shown by PCR to be infected with Candidatus Liberibacter asiaticus (Las). Large differences were noted between rootstocks for many metrics examined, including yield, fruit quality, and tree size. Highest yields in the trial were on US-942 rootstock, which was significantly more productive than trees on the common commercial rootstocks Carrizo, Kuharske, Cleopatra, and Kinkoji. Other new hybrid rootstocks also performed well in this trial strongly affected by HLB, including the rootstock US-1516, which had the second highest cumulative yield, best tree health rating, and lowest number of trees lost due to HLB damage. Comparison of tree performance in this trial with a similar trial conducted prior to the HLB epidemic, allows us to estimate that the disease resulted in a 33% reduction in yield and 21% reduction in tree growth through seven years of age. Use of a tolerant rootstock is suggested as an effective means of ameliorating crop losses to HLB.