2018 ASHS Annual Conference

Since the strike of four hurricanes in South West and Central Florida in 2004 (Charley, Frances, Ivan and Jeanne), and then Wilma in 2005, citrus growing areas in the state were hurricane-free for more than a decade. However, the disease known as citrus greening or HLB was first detected in Florida in 2005. Under HLB pressure, that has decreased production by 70% in 10 years, Florida Citrus Industry has adopted several strategies to survive while coping with the disease, since it is now endemic and there is no cure currently available. These strategies include, but are not limited to, developing and testing new varieties (rootstocks and scions) with tolerance to the disease. On September 10^th, 2017 Irma made landfall as a cat 4 hurricane in South West Florida, severely affecting citrus groves aligned in her path. As a result, USDA Citrus Crop Forecast for this year has dropped from roughly 70 to about 45 million boxes. Being the situation dramatic for the Industry, still there was useful information during Irma’s aftermath that we have been able to share with the rest of the citrus community in our state. In addition, these observations have seeded new research initiatives. Examples include rootstock behavior in response to winds and survival of new varieties after extensive flooding and wind damage. Trees from Hamlin and Valencia grafted on different rootstocks behaved differently in response to hurricane-force winds: Around 50% of trees grafted on the trifoliate dwarfing rootstock ‘Flying dragon’ were uprooted, whereas this only happened on less than 6 % of trees on Swingle citrumelo or Cleopatra mandarin, irrespective of the scion. The mandarin hybrid LB8-9, also known as SugarBelle [Clementine’ mandarin (Citrus reticulata) × ‘Minneola’ tangelo] has shown tolerance to HLB and is now being adopted by many growers in Florida willing to produce high quality mandarins for the fresh market. In an experimental plot of 6-year old trees grafted on Carrizo rootstock, winds uprooted 70% of the trees. These trees were laying on the ground for up to three weeks before planted back. After winter, all the trees have survived, and spring flush, flowering, and fruit set was more abundant and occurred two weeks earlier as compared to standing trees. Taken together, these data increase our understanding and will lead to better management of stresses associated with hurricane conditions, allowing citrus growers to make better decisions in a timely manner.