Citrus huanglongbing (HLB) has been recognized for a century yet control and management remain elusive despite over 90 years of intensive research. The bacterial pathogen is an insect endosymbiont that was most likely inadvertently introduced into citrus where it found a compatible environment for growth in citrus phloem cells and therefore jumped from the animal to plant kingdom. Because the genus citrus did not coevolve with the bacteria it has no resistance and little tolerance to it and the resulting vascular disease is severe. The winged insect vector of the bacteria, the Asian citrus psyllid (ACP), is an exotic introduced species in its own right, prolific, and difficult to control even on a regional spatial scale. The resulting disease has a long latent period prior to symptom expression and a challenging cryptic period during which detection by convention PCR and other methods can be elusive. The result is an unusually rapid increase and spread of the resulting disease. This article offers some nonconventional perspectives to examine this unusual and devastating pathosystem to stimulate though toward improved control/mitigation.

Field data on intensity of plant diseases is very often irregularly spaced (i.e., there are varying amounts of distance between rows, ponds, voids, roads, houses, or other land areas). Typically, this type of data is gridded and the average disease intensity of the plants within the grid is used instead of the original data on each separate plant. This is done because the underlying statistical assumptions in the analysis of spatial data usually require that data be equally spaced. However, a new method of analysis, sometimes called second-generation wavelet analysis, can be used on irregularly spaced spatial data. Wavelet analysis is a method used to analyze variations in scale and position of non-stationary spatial signals (non-stationary for our data means the statistical properties can vary based on location within the orchard), and the second-generation refers to an iterative process, called a lifting scheme (1), which allows for the irregular spacing. Irregular spacing is often found in citrus groves as spacing within and between rows is often not uniform, and on a larger spatial scale, distance between blocks and plantings are not necessarily simple multiples of distances between rows and trees. In addition, there are a number of other issues such as missing trees, the presence of irregular roads, ponds, staging areas, etc., that cause citrus groves to have irregular distances between trees when viewed at the plantation or regional scale. Therefore, to test this new method, we conducted a second-generation spatial wavelet analysis on a large irregularly spaced citrus planting (Southern Gardens) in Florida where over 260,000 trees were assessed for incidence of huanglongbing (HLB) over five sampling times.

Florida citrus production from 1980-2021 was examined and modeled to determine the impacts associated with weather events and disease introductions.  Specifically, the study examined the effects of North Atlantic hurricanes, freezes events and two disease introductions -- Asiatic citrus canker (ACC), and Huanglongbing (HLB) -- on productions levels and on the structure of the Florida citrus industry.  The models estimated quantified the effects on production associated with the weather events and disease introductions.  Using the deterministic model generated, forecasts were generated to identify future implications of HLB on Florida citrus production.  Theses generated forecasts were compared to actual production levels and the USDA Crop forecast to test and validate the model.  Whereas testing indicated a significant structural change in the Florida citrus industry resulting from adverse weather events and disease introductions, published economic impact studies were examined and reviewed to gage the resulting reduction in total economic impact.