Examining the Effects of Induced Plant Defenses on Spodoptera frugiperda Performance

Abstract

Knowing the duration insect pests are in the environment is vital for growers to determine management schemes and apply treatments. Unfortunately, experiments to determine long-term insect performance across plant cultivars are infrequently conducted. With that in mind, we report here the performance of Spodoptera frugiperda, the fall armyworm, on jasmonic acid (JA) induced/non-induced soybean cultivars. JA induction increases plant defensive compounds and can be considered an equivalent to a plant’s response to herbivory. S. frugiperda is a global pest, with infestations in soybeans becoming an emerging problem, making information on this pest’s performance on soybeans warranted. Thus, we reared larvae on two different soybean cultivars with contrasting defensive strategies when induced with JA and measured 7-day survival, development time to pupation, and pupal mass. Plant cultivar and JA induction were both important causes of mortality. Although plant cultivars varied in their amounts of constitutive/inducible defenses, this did not cause an interactive effect between plant cultivar and induction. Insect development to pupation was also extended when fed on induced plants regardless of cultivar, while pupal mass was not affected. Overall, induced plant defenses lowered larval survival and extended development time which would alleviate pest pressure and extend the period growers have for detecting infestations.