Action Thresholds for Fall Armyworm on Grain Sorghum and Coastal Bermudagrass

Abstract

Under the present (1980) economic conditions, action thresholds for fall armyworm Spodoptera frugiperda (J. E. Smith), on grain sorghum have been estimated to be (1) 10% of seedling sorghum possessing egg masses, (2) 1 larva/shoot in the whorl stage, and (3) 2 larvae/head after flowering. In coastal bermudagrass the action threshold is between 2-10 larvae < 3/8 in. long/ft.^2. It is common for economic or action thresholds to range from guesses to thoroughly-tested management tactic initiation guidelines. Nevertheless, the action threshold concept is needed in high-energy, fossil-fuel dependent agriculture systems to increase short-term profits and reduce conventional pesticide usage. Important factors to consider in the development of action thresholds for fall armyworm are: weather, soil types, crop culture, other herbivores, and entomophagous arthropods which affect both the fall armyworm and the host crop, as well as the ecosystem in which they are found. An alternative to the development of complex dynamic action thresholds for use in high energy systems is the use of insect insurance; this should be considered in conjunction with or in place of action thresholds. As we transcend to low-energy, holistically-managed systems, there should be much less of a need for action thresholds in our agroecosystems since these systems must be designed to prevent, avoid, evade, circumvent, and suppress pest problems.