Rootstock impacts on citrus flush dynamics, vegetative growth, and Diaphorina citri infestation and dispersion: Implications for huanglongbing management

BACKGROUND: Citrus tree vigor is regulated mainly by the rootstock. It may affect vegetative flushes and the dispersal and infestation of Diaphorina citri (Asian citrus psyllid) within the orchard, contributing to the inoculation of the huanglongbing (HLB) bacterium. We conducted an experiment using the sweet orange cv. Hamlin grafted onto two rootstocks of contrasting vigor: the vigorous 'Sunki Tropical' mandarin and the dwarfing 'Flying Dragon' trifoliate orange. The study aimed to investigate the impact of these rootstocks on tree growth, vegetative flush dynamics, psyllid infestation and dispersal, HLB progression, yield, and fruit quality in a young orchard. RESULTS: Psyllid infestation was strongly associated with the presence of flushes in a given period. Trees on vigorous rootstocks exhibited profuse growth, larger canopies, and longer, more abundant flushes, offering greater resources for psyllid feeding and reproduction over time. In contrast, trees on dwarfing rootstocks had smaller canopies and fewer, shorter shoots (50% shorter than vigorous), resulting in reduced psyllid abundance for these trees as a host in our study. HLB progression was slower in dwarfed trees throughout the evaluation period; however, by 43 months after planting (MAP), disease incidence and severity increased, resulting in similar levels between treatments. Our findings indicate that dwarfing rootstocks have the potential to integrate management strategies to reduce psyllid populations and, consequently, HLB progression under strict control of the insect vector, even in areas with high disease incidence. CONCLUSIONS: Dwarfing rootstocks, such as 'Flying Dragon,' significantly restrict vegetative growth and flush development, thereby reducing available feeding and oviposition sites for psyllids, offering a promising component in integrated HLB management strategies by lowering vector populations and disease spread potential.