Impact of Fall Armyworm (Lepidoptera: Noctuidae) Host Strains on the Evaluation of Bermuda Grass Resistance1

Abstract

Development and survival of two fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), host strains were evaluated on four varieties of Bermuda grass, Cynodon dactylon (L.) (‘Coastal’, ‘Grazer’, OSU 71 × 6–7, and ‘Tifton 292’). Two FAW laboratory colonies used in experiments were analyzed electrophoretically and determined to comprise the corn strain (GA colony) and the rice/Bermuda grass strain (LA colony). Comparisons between strains indicated significant developmental differences on ‘Tifton 292’ and, to a lesser degree, on ‘Coastal’. On the former, larvae from the LA colony were 3 times heavier on day 8 and developed about 3 d faster than larvae from the GA colony. Differences in survivorship were not significant. Development on the four varieties also differed within strains. The LA colony exhibited the best developmental performance on ‘Tifton 292’, whereas that variety was worst for development of the GA colony. Thus, a variety considered resistant when tested with the corn strain conferred no resistance to the rice strain. In nature, the rice strain predominantly feeds on Bermuda grass. The host strain of laboratory colonies used to assess host plant resistance to FAW cannot be ignored.