Cold hardy citrus is an emerging industry in north Florida. However, it is under the threat of Candidatus Liberibacter asiaticus (CLas), the agent of the citrus disease huanglongbing. Distribution and phenology of the Asian citrus psyllid, Diaphorina citri (Kuwayama), the vector of CLas, was investigated over a 2-year sampling period in north Florida. Diaphorina citri was only found in backyard and ornamental citrus along the Gulf of Mexico, and was not observed in cultivated citrus groves during the 2 years (2017–2018) of the survey. Diaphorina citri population peaks occurred approximately 2 mo later than in central Florida with major population peaks occurring in July. The number of D. citri adults was significantly higher on CLas infected than uninfected citrus trees, whereas more nymphs were found on uninfected trees. Most D. citri were negative for CLas except in Franklin county where both infected trees and psyllids were found. We were able to find adult D. citri during all winter months, despite temperatures as low as –5.5°C. During two consecutive winters, we conducted experiments to determine D. citri cold hardiness by caging D. citri under ambient conditions in mid-November and assessing survivors in the following spring. In 2018, approximately 21%, of D. citri adults survived overwintering whereas 16% survived in 2019 despite lower temperature in 2018 than in 2019. As we are at the earliest stage of HLB infestation, management of D. citri and CLas in north Florida should focus on removal of CLas-infected trees to reduce the reservoir of pathogen.
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Vol. 113 • No. 3