Bermudagrass Allelochemistry and Influence on Spodoptera frugiperda Herbivory

Cultivated area of bermudagrass (Cynodon dactylon L. Pers.), in the USA are under stress from a complex of insect and secondary fungal pests which has resulted in a loss in crop production. The fall armyworm (Spodoptera frugiperda (J.E. Smith)) is the major insect herbivore of bermudagrass in the south-eastern USA. Bermudagrass breeding programmes over the last decade have yielded germplasm with potential insect-resistant traits. Thus, a programme was initiated to define bermudagrass allelochemislry with respect to insect herbivory. Pall armyworm is variably responsive to bermudagrass cultivars, the basis being causally related to a differential concentration of the phagostimulant 6, I 0, 14 trimethylpentndecnn-2-onc. The nutritional suitability of bermudagrass to herbivory was cultivar-dependent and associated with a variable profile of several key essential dietary lipid components. These included polyunsaturated falty acid esters, vitamin E, and the sterols: campesterol, stigmasterol, and sitosterol. A differential accumulation of an active feeding deterrent was also found to vary among cultivars.