The major alkaloid produced is the indole alkaloid, ergovaline. The endophyte grows between the plant cells. It is most proliferative in the spring, and closely associates with the growing flower and seed head. It is through contamination of the seed that infection of fescue is spread. Plant to plant or field to field transmittion of the endophyte is very limited.
Tall fescue produces the two diazaphenanthrene alkaloids, perlolidone and perloline.
Under lab conditions, administrating perloline to sheep has caused mild photosensitivity, increased pulse and respiration rates, loss of muscle control, convulsions, and comas. However, perloline and perlolidone do not appear to be responsible for the fescue toxicities observed under field conditions. Rather, alkaloids produced by the endophyte appear to be the culprits. Acremonimum coenophialum produces both loline and ergopeptine classes of alkaloids. The lolines are saturated pyrrolizidine alkaloids with mild vasoconstrctive properties.