Threats of Tar Spot Complex disease of maize in the United States of America and its global consequences

The emergence and spread of new crop diseases threatens the global food security situation. Phyllachora maydis, one of the three fungal pathogens involved in Tar Spot Complex (TSC) of maize, a disease native to Latin American countries, was detected for the first time in the United States of America (USA) in 2015. Although TSC has been previously reported to cause up to 50% of yield losses in maize in Latin America, the impact of P. maydis alone on maize yield is not known yet. However, there is a possibility that Monographella maydis, the second most important pathogen involved in TSC, would be introduced to the USA and would become associated with P. maydis and both pathogens could form the devastating complex disease in the country. The first objective of this study was to identify the TSC-vulnerable maize-producing regions across the USA by applying a climate homologue modeling procedure. The second objective was to quantify the potential economic impact of the disease on the maize industry in the USA. This study showed that even a 1% loss in maize production caused by the disease could potentially lead to a reduction in maize production by 1.5 million metric tons of grain worth US$231.6 million. Such production losses will affect not only the maize-related industries in the USA but also the food security in a number of low-income countries that are heavily dependent on US maize imports. This, in turn, may lead to increased poverty and starvation and, in some cases, to social unrest due to increased prices of maize-based staple foods. The study is intended to raise public awareness regarding potential TSC outbreaks and to develop strategies and action plans for such scenarios.