Kirsten Hannam

Agriculture and Agri-Food Canada | AAFC · Science and Technology Branch

In the past 2-3 years in Canada, fruit trees including apple, pear and apricot, have shown evidence of serious and unprecedented mortality rate exceeding 40%. This fruit tree decline is evident in apples and tender fruits, and may be caused by a complex combination of biotic and abiotic stresses. Symptoms of decline leading to mortality have been reported in Ontario, British Columbia, Prince Edward Island and Nova Scotia. Preliminary research and literature reports have identified bacterial, fungal, nematode, arthropod and viral agents as biotic contributing factors. A thorough understanding of the etiology of the causal agent(s) is vital for preventing the spread of these diseases and minimizing their affects on tree fruit production in Canada. In apples, this disease is known as Sudden Apple Decline (SAD). SAD occurs rapidly, with tree mortality occurring within a few weeks following the onset of symptoms. Apple Luteovirus 1 was recently identified in diseased trees but it is not clear if this virus is responsible for SAD. In Ontario, British Columbia and Prince Edward Island, a second tree decline disease was recently reported in tender fruits. We have called this disease Tender Fruit Tree Decline (TFTD). TFTD proceeds slowly over 2-3 years before tree death, with yellowing of leaves, vasculature rot, stunted growth and poor fruit set. We have identified Tomato ringspot virus in symptomatic apricot trees, but it is unlikely that this pathogen alone, is causing this mortality. Both SAD and TFTD are likely caused by a complex combination of pathogen pressures and abiotic factors. Identifying causal agents of SAD and TFTD are the primary objective of this proposal. The research team assembled to identify these causes will include a diverse and multidisciplinary team of highly qualified AAFC scientists across Canada. Microbiology, nematology, entomology, physiology, plant pathology, genomics and molecular biology will be used to identify pathogens related to these syndromes. Once major pathogens have been identified, we will determine their contributions to diseased fruit trees by following Koch's postulates. The overarching goal is divided into two main objectives: identification of pathogens and abiotic factors including characterization of tree fruit decline symptoms associated with individual pathogens, and implementation of Koch's postulates to conclusively demonstrate which pathogen(s) are required for the characteristic diseases symptoms in apple and tender fruit. The positive identification of contributing pathogens to fruit tree decline, will then allow the development and implementation of future integrated management practices for the control of tree fruit decline in Canadian orchards.

The main goal of this project is to summarize the methods and results of forest wood ash amendment trials across Canada (AshNet: http://www.nrcan.gc.ca/forests/research-centres/glfc/ashnet/20279) with the aim of informing future wood ash amendment research and exploring the potential benefits of wood ash amendment practices.

To better understand the effects of irrigation practices on soil nitrogen and soil organic and inorganic C storage. Research will be conducted on sites with a range of soil types, crops, and irrigation practices in the semi-arid Okanagan Valley, British Columbia. Our ultimate goal is to identify management practices that best mitigate greenhouse gas emissions while maintaining crop productivity and enhancing soil health.