An open access repository of images on plant health to enable the development of mobile disease diagnostics through machine learning and crowdsourcing

Human society needs to increase food production by an estimated 70% by 2050 to feed an expected population size that is predicted to be over 9 billion people. Currently infectious diseases reduce the potential yield by an average of 40% with many farmers in the developing world experiencing yield losses as high as 100%. Infectious diseases of crops are not new and historic examples such as the Irish Potato Famine of 1845-49 demonstrate this. But what is new is the widespread distribution of smartphones among crop growers around the world with an expected 5 billion smartphones by 2020. This offers the potential of turning the smartphone into a valuable tool for diverse communities growing food. One potential application is the development of mobile disease diagnostics through machine learning and crowdsourcing. Computer vision and machine learning have shown their potential to automatically classify images. To do this for plant diseases requires a training set that facilitates the development of the algorithms. Here we announce the release of >50,000 expertly curated images on healthy and infected leaves of crops plants through the existing platform www.PlantVillage.org. We describe both the data and the platform. These data are the beginning of an on-going, crowdsourcing effort to enable computer vision approaches to help solve the problem of yield losses in crop plants due to infectious diseases. Keywords: plant pathology, food security, machine learning, crowdsourcing The origins and continued evolution of agriculture in the face of infectious diseases and pests Perhaps the greatest technological advance that humans have ever made has been the domestication of plants during the agricultural revolution 8-12,000 years ago at multiple sites around the world (Diamond 2002).These events literally created civilizations through the steady, predictable supply of calories that could be obtained with lower and lower amounts of energy expended through human work. The enormous increase in human population from around 1 billion in the early 1800s to our current situation of over 7.2 billion has been made possible by an efficient and productive agricultural basis (Borlaug 2000). However, this steady supply of calories is currently threatened, as many of the advances resulting from the Green Revolution of the 1950s are failing due to infectious diseases and pests spread by globalization and compounded by climate change (Bourne 2015). Diseases of plants are not new of course. Many histories have recorded the enormous impact that infectious diseases have had on growing food crops (Ainsworth 1981). The iconic example is the Irish Potato famine of 1845-49 where an overdependence on a single crop with little genetic diversity set the stage for a devastating decline in yield that resulted in 1.2 million deaths out of a population of 9 million (Woodham-Smith 1991). At the time, plant diseases were poorly studied and the Irish Potato famine is widely identified as the event that began the scientific discipline of plant disease (Carefoot and Sprott 1967). It also marks the formal system of extension where science based knowledge is provided to farmers by state employed extension workers (Jones and Garforth 2005). In the intervening 170 years, plant pathology has grown to become a robust discipline offering crop growers multiple solutions from chemical control to genetic engineering to integrated pest management. At the same time, formalized extension systems have likewise developed to provide knowledge to growers. But the fact that the global food supply is annually reduced by an average of 40% (Oerke 2006) demonstrates that our collective battle against diseases and pests of crop plants is not won. In fact, the emergence and spread of novel and highly virulent crop diseases like the stem rust UG99 that attacks wheat, black pod in Cocoa and viral infections of Cassava suggest that the situation may in fact be worsening. This is troubling at a time when the UN FAO recommends we must in fact increase the food supply by 70% to feed the future population. The effect of modern agriculture is not just its ability to feed large populations in the face of disease threats. Given the long history we humans have had in growing food, it is not surprising that how we grow food shapes the social, psychological, and physical development of individuals and communities. In a large study of communities of rice and wheat farmers in China, for example, researchers found rice farming changed people’s psychology, resulting in more interdependent communities (Talhelm et al. 2014). Recently, two studies recorded how the transition from hunter-gatherers to farmers reduced the strength of our bones (Chirchir et al. 2015, Ryan and Shaw 2015) and teeth (Pinhasi et al. 2015). And at the societal level it is a truism that no country has achieved economic independence and a strong manufacturing sector without first developing a strong agricultural sector. This was (regrettably) demonstrated in a number of African countries in the 1950s which, post-independence, abandoned a system of coordinated agricultural knowledge development and dissemination in favor of industrial growth (Eicher 1999). The result was a weakened agricultural sector that still exists today which 1	  http://www.fao.org/fileadmin/templates/wsfs/docs/expert_paper/How_to_Feed_the_World_in_2050.pdf necessitates the efforts by the Alliance for a Green Revolution in Africa (AGRA) (Sanchez 2015). Therefore, an examination of humans at the psychological, physical and societal levels demonstrates that, as an agent of change, agriculture is one of the most potent. Agriculture is culture. And like all human culture, it is constantly evolving. For example, in the USA, the way people have farmed -and what proportion of the population actually farmshas shifted considerably. These changes reflect increased urbanization and greater efficiency at the farm level via the incorporation of new technologies from fertilizers and pesticides to better farm machinery, to more recent advances such as precision agriculture and Genetically Modified Crops. In America in 2015, few people are fully engaged as farmers; less than 1% of the entire population according to the United States Department of Agriculture (Woteki 2012). It would be easy to think that food growing is not that relevant to most Americans or other members of countries in the industrialized west. But of course that is not true. A cursory glance at the media shows an increasingly high level of concern about food production, and many people express unease at the dominance of Big Ag (e.g. Monsanto), the increased focus on growing monocultures (e.g. corn) for both meat production and biofuels, and of course the public concern over GMOs (Bourne 2015). Perhaps reflecting this change is the growing movement called the New American Farmer (Bartling 2012). Since the 1980s we have witnessed an increase in smallholder farmers that seek to promote diverse practices and crops. The essence of such movements were captured in Michael Pollan’s book, The omnivore's dilemma: a natural history of four meal (Pollan 2006). Recognizing this, public health institutions are increasingly encouraging consumers to grow their own food, as both the process of growing food (exercise through gardening) and the yield (fresh fruit and vegetables) contribute to beneficial public health outcomes. Indeed, gardening, and urban gardening in particular, has become increasingly popular in the past two decades, reversing a long trend of consumers becoming less and less involved in growing their food. Globally, Google Trends captures this and reports a steady increase of interest in "urban gardening" . Whereas many communities in the developed world countries are choosing to grow foods at small scales, in the developed world such small-scale farming is the norm. This is an imposed necessity rather than a choice. In many countries (e.g. those in SubSaharan Africa) as much as 80% of the population are farmers with single families growing diverse crops on small (2-5 hectare) plots with minimal mechanical or chemical (fertilizer, pesticides) inputs (Sanchez 2015). At this scale the relative impact of yield gaps (the gap between potential and actual yield) is very high (Collier and Dercon 2009, Foley et al. 2011). A consistent wedge reducing our ability to close this gap are infectious diseases and pests. Since most subsistence agriculture today occurs around the tropics and since the biodiversity of all infectious diseases (of humans, animals and plants) is higher in the tropics then the pressure of diseases are greatest in these areas. It is commonplace for smallholder farmers to routinely lose 80-100% of a given crop to pests and diseases (Oerke 2006). Taken together then we can see that agriculture is an ancient technology of great relevance to both human society and human psychology and that it is currently practiced around the world in diverse modes that are under constant cultural evolutionary change. In a world that increasingly hot, flat and crowded the importance of growing enough food 2	   https://www.google.ch/trends/explore#q=Urban%20gardening cannot be overstated. The difficulties are many but largely revolve around the need to close the yield gap by reducing losses due to diseases, pests and poor management practices. In the 170 years since the Irish Potato famine we have learned a considerable amount about the science of reducing the yield gap. But our current situation of diverse food growing arenas from community gardens to mega farms to smallholder farms has meant that finding relevant knowledge can be difficult. Depending on the country and location of the food grower, they may have access to professional services providing help. For many professional growers crop insurance mitigates the losses. Further, in many countries, extension services provide critical support dealing with th