Lethal bronzing is a bacterial disease that kills more than 20 species of palm trees in the Southern United States and the Caribbean and has been devastating Florida's green industries for nearly two decades. This disease has been causing a significant decrease in palm trees. In a recent discovery made by Embrapa Environment research fellow Jordana Ferreira, during her postdoctoral studies through the University of Florida under the supervision of researcher Sônia Queiroz and funding by FAPESP, it was observed that palm trees infected with bronzing release high concentrations of volatile compounds, which warn nearby healthy palms of a possible threat. According to Ferreira, the research findings showed that infected, injured or stressed palm trees released volatile chemical compounds such as E-2-hexenal and hexanal, causing nearby healthy plants to activate the production of other compounds such as 3-hexenal and Z-3-hexen-1-ol to potentially ward off the pest responsible for the disease. "Plants that were not close to infected plants and under no threat would not release the volatile compounds. These results were published in the journal Plants, in the paper entitled "Identification of Green-Leaf Volatiles Released from Cabbage Palms (Sabal palmetto) Infected with the Lethal Bronzing Phytoplasma". Ferreira also asserted that those results are important because it is the first documented record of such green leaf volatile compounds in palm trees infected by the bacteria that cause lethal bronzing. "It was observed that the volatile compounds produced by the palm trees have antimicrobial properties," she explains. "This contributes to understanding the epidemiology of lethal bronzing in the fields. In addition, such natural volatile compounds can be used in new bioinput formulas to treat palm trees or stimulate their defenses,” she believes. For Embrapa Environment researcher Sônia Queiroz, one of the biggest advantages in assessing the volatile compounds from samples taken from the field is that the volatile compounds are produced in the early stages of infection. She remarks that when symptoms are noticeable, it may be too late for remediation. Because there is no effective treatment yet, the solution has been the elimination of infected plants to prevent the bacteria from spreading. Currently in the USA the disease is treated with the synthetic antibiotic oxytetracycline as a preventative measure, which not only is expensive but also does not have satisfactory results. Since the volatile compounds have antimicrobial properties, more environmentally friendly bioinputs can be produced to replace the synthetic ones used. Importance in the USA Palm trees play an important role in the South Florida landscape in the United States due to their many environmental, cultural, and economic contributions. In addition to aesthetics and landscaping, which are very strong in this region, palm trees contribute as protection against flooding by adsorbing rainwater and reducing the impact of floods, as the leaves work as suction pumps through the evapotranspiration of those rains. This is important because South Florida is located in a swampy area, where water adsorption is hindered by soil saturation, water accumulation, low permeability and the high level of water table. In addition, their ideal weather conditions like temperature, humidity and winds favor the cultivation of palm trees in the region. However, the native palm species known as Sabal palmetto has been facing serious problems with the spread of the lethal bronzing disease transmitted by the planthopper Haplaxius crudus, which, if infected by the phytoplasma (a type of bacteria), can transmit the disease to the plant as it feeds on the leaves. The phytoplasm then multiplies, causing suffocation in the phloem, and subsequent death of the plant. Soon after the first symptoms of the disease, in a few months, the entire canopy dies and only the stem is left, as shown in the photo below. Photo: Jordana Ferreira. The full paper by Jordana Ferreira (Embrapa Environment); José Ramos (Nova Southeastern University); Débora Dutra (Embrapa Environment); Brandon Di Lella, Ericka Helmick (Nova Southeastern University); Sônia Queiroz (Embrapa Environment) and Brian Bahder (University of Florida), published on Plants 2023, can be accessed here.