The objective of this study was to integrate data on the effect of water activity ( a _w ; 0.995–0.93) and temperature (20–35°C) on activation of the biosynthetic FUM genes, growth and the mycotoxins fumonisin (FB ₁ , FB ₂ ) by Fusarium verticillioides in vitro . The relative expression of nine biosynthetic cluster genes ( FUM1 , FUM7 , FUM10 , FUM11 , FUM12 , FUM13 , FUM14 , FUM16 and FUM19 ) in relation to the environmental factors was determined using a microarray analysis. The expression was related to growth and phenotypic FB ₁ and FB ₂ production. These data were used to develop a mixed-growth-associated product formation model and link this to a linear combination of the expression data for the nine genes. The model was then validated by examining datasets outside the model fitting conditions used (35°C). The relationship between the key gene ( FUM1 ) and other genes in the cluster ( FUM11, FUM13, FUM9, FUM14 ) were examined in relation to a _w , temperature, FB ₁ and FB ₂ production by developing ternary diagrams of relative expression. This model is important in developing an integrated systems approach to develop prevention strategies to control fumonisin biosynthesis in staple food commodities and could also be used to predict the potential impact that climate change factors may have on toxin production.