Citizen Scientists Help Us Understand Plant Diseases

          When trying to elucidate infectious disease dynamics, it is necessary understand spatial and temporal patterns of the species being infected as well as the species that is infectious. When studying plant infectious disease, this means that it is necessary to have robust and up to date data on where the plant is located, and geographically where the plants are being infected. If the disease has a broad range, then the task of gathering up-to-date, robust data is extremely difficult for scientists on their own. Additionally, most data collected by scientists comes from plants on public lands, which leaves a gap in understanding plant diseases on private lands.  

            Meentemeyer et al. recognized citizen science projects as a means to increase data sets and improve knowledge of Sudden Oak Death (SOD), a disease caused by Phytophthora ramorum. In 2008, Meentemeyer et al. founded Sudden Oak Death Blitz, a community science program in California that trains community members to collect leaf samples from oak trees infected with SOD. Each volunteer is able to send in 16 leaf samples, and the location of each sample site is tracked through GPS within a mobile application. Figure one shows the data available for geographic distribution of SOD before and after SOD Blitz. The presence or absence of P. ramorum is verified in a laboratory through Polymerase Chain Reaction (PCR) and ribosomal DNA sequencing. From 2008 to 2013, SOD Blitz had over 1,600 community science volunteers. Prior to the program, they were able to predict P. ramorum infections with 65% accuracy (2008). In 2013, after five years of the program, they were able to predict with 78% accuracy. Additionally, for each year of the program, community science volunteers have had an equal or higher ratio of infected leaves: non infected leaves than self-reported expert volunteers. This indicates that with some training, community scientists can collect samples as effectively as self-reported experts.

Figure 1: On the left are SOD sampling sites pre-SOD Blitz program. On the right are SOD sampling sites five years into the program (2013). Red dots represent infected samples, while green squares represent uninfected samples. 

            The success of SOD Blitz suggests that similar community monitoring programs could be useful in helping scientists understand other plant diseases. One potential opportunity would be to implement a similar program to study bur oak blight (BOB) in the Midwest. BOB is leaf spot disease caused by fungus, Tubakia iowensis which occurs primarily in Iowa and Minnesota (figure 2). Harrington et al. have suggested that the recent increase in BOB may be related to the increase in spring rains in the Midwest. With climate change, it is predicted that Iowa will have increased spring rainfall, so it would be interesting to further investigate the connection between rainfall and BOB disease progression.  Harrington et al. have performed some observations on BOB’s distribution (figure 2), but a community science monitoring program would help expand the data set and monitor disease progression over time in an efficient manner. By creating a long-term program similar to SOD Blitz, we would be able to better understand the dynamics of T. iowensis infections in bur oaks. Additionally, a community science approach could help to engage the public in the process of science and instill an appreciation for the envrionment. 

Figure 2: Geographic distribution of T. iowensis. Red represents counties where T. iowensis presence has been confirmed. Gray represents counties where T. iowensis has not been found as of July 2016.

References:

Meentemeyer, R.K.; Dorning, M.A.; Vogler, J.B.; Schmidt, D.; and Garbelotto, M. 2015. Citizen Science Helps Predict Risk of Emerging Infectious Disease. Frontiers in Ecology and the Environment. 13: 189–194.