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This study examined the effect of climate change (CC) abiotic factors of temperature (20, 25, 30 degrees C), water activity (a(w); 0.995, 0.98) and CO2 exposure (400, 1000 ppm) may have on (a) growth, (b) gene expression of biosynthetic toxin genes (Tri5, Tri6, Tril6), and (c) T-2/HT-2 toxins and associated metabolites by Fusarium langsethiae on oat-based media and in stored oats. Lag phases and growth were optimum at 25 degrees C with freely available water. This was significantly reduced at 30 degrees C, at 0.98 a(w) and 1000 ppm CO2 exposure. In oat-based media and stored oats, Tri5 gene expression was reduced in all conditions except 30 degrees C, 0.98 a(w), elevated CO2 where there was a significant (5.3-fold) increase. The Tri6 and Tril6 genes were upregulated, especially in elevated CO2 conditions. Toxin production was higher at 25 degrees C than 30 degrees C. In stored oats, at 0.98 a(w), elevated CO2 led to a significant increase (73-fold) increase in T2/HT-2 toxin, especially at 30 degrees C. Nine T-2 and HT-2 related metabolites were detected, including a new dehydro T-2 toxin (which correlated with T-2 production) and the conjugate, HT-2 toxin, glucuronide. This shows that CC factors may have a significant impact on growth and mycotoxin production by E langsethiae. (C) 2019 Published by Elsevier Ltd on behalf of British Mycological Society.