Phoma betae, causative agent of seedling, foliar, and root diseases, is an important pathogen of table and sugar beet worldwide. Little is known of the epidemiology and management of diseases caused by P. betae in New York (NY) table beet production systems. This research was conducted to understand the population biology of P. betae in table beet in NY and evaluate management options for the foliar disease caused by P. betae, Phoma leaf spot (PLS). Microsatellite and mating type markers were developed to genotype P. betae populations, and population biology analysis was performed to investigate hypotheses concerning pathogen biology and the role of various inoculum sources in PLS epidemics. High genetic diversity and moderate differentiation was observed among populations, along with evidence for a mixed reproductive mode. Development of these genetic tools will facilitate future studies targeting specific epidemiological questions. Field surveys were conducted in the summers of 2017 and 2018 to estimate prevalence, incidence, and severity of PLS epidemics in conventional and organic NY table beet production systems. PLS was found in 35 of 60 fields with incidence up to 31% in affected fields. The prevalence of PLS in organic table beet fields (74%) was higher than in conventional fields (49%). This research also focused on the potential of cultivar resistance to form part of an integrated management strategy for PLS in organic production. Eight popular table beet cultivars were evaluated for susceptibility to PLS and horticultural characteristics in mist chamber and small plot, replicated trials. Non-red cultivars (Avalanche, Boldor, and Chioggia Guardsmark) were consistently less susceptible to PLS than red cultivars (Falcon, Merlin, Red Ace, Rhonda, and Ruby Queen). Information from this research will be used to strengthen durable management strategies for this disease in NY.