The Citrus Grove of the Future and Its Implications for Huanglongbing Management

Revolutionary changes face Florida’s citrus industry as huanglongbing (greening) becomes widespread. Changing economic realities have encouraged many tree fruit industries to modify planting density, tree architecture, training and production systems. More trees/acre translate into earlier bearing and less yield disruption as trees die, but with greater establishment costs per acre. A model for citrus production, which may permit profitable production in Florida using huanglongbing susceptible material, has been called an Advanced Production System combined with Open Hydroponic System. These practices have been adopted in a number of citrus producing countries, but need to be evaluated and adapted to Florida conditions. Practices that facilitate early cropping and fruit quality are critical to high density orchard profitability. Control of water and nutrients to manage tree development, girdling, use of plant growth regulators, larger planting stock, and tree supports may maximize early yields and help contain canopy volume. In the more distant future, genetic improvement solutions may contribute additional tools. The purpose of this paper is to stimulate discussion, facilitate assembly of diverse useful ideas in facing this challenge, and coordinate efforts within Florida to get a critical mass of production and economic data as quickly as possible. The Florida and U.S. citrus industries are facing an unprecedented crisis. It is projected that with the current rates of spread and increase, virtually all current citrus plantings in Florida will be affected by huanglongbing (HLB) in 7–12 years (T. Gottwald, personal communication). Total Florida citrus production will decline in this period in the absence of any offsetting options. For the long-term future of Florida citrus, the greatest threat may be that a significant lapse in citrus production could result in the permanent loss of the processing and packing infrastructure, which requires a high level of throughput to remain viable (R. Norberg, personal communication). Psyllid-control and/or HLB-detection and tree roguing solutions may be found that will protect existing groves (Bove, 2006), but those solutions alone may take too long to sustain the volume of fruit production necessary to maintain a viable industry. Thus, it is critical to develop new procedures that permit economically acceptable production in new plantings until long-term solutions such as pest/disease control measures, HLB-resistant transgenics, or other “sustainable” practices are identified and implemented. The purpose of this paper is not to provide answers obtained through research, because there are no solid answers currently available. Indeed, it appears that the industry needs guidance sooner than the established research verification/extension/industry adoption paradigm can possibly provide it. It is our intent to mobilize the research community and industry to establish a coordinated series of research plots, which will provide reasonable guidance to industry decision makers, so that they can rationally consider establishing extensive new groves which may provide the fruit production necessary to sustain the processing and packing infrastructure.