Variation in invasive plant lineages of an agricultural weed affect insect herbivore

Authors: Arismendi Baena, Giselle; MINTEER, C - University Of Florida; FLORY, S - University Of Florida; BROOKES, DEAN - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Wheeler, Gregory

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2026
Publication Date: 6/17/2026
Citation: Arismendi Baena, G., Minteer, C.R., Flory, S.L., Brookes, D., Wheeler, G.S. 2026. Variation in invasive plant lineages of an agricultural weed affect insect herbivore. Biological Control. 29. https://doi.org/10.1016/j.biocontrol.2026.106091.
DOI: https://doi.org/10.1016/j.biocontrol.2026.106091

Interpretive Summary: Cogongrass is one of the worst invasive weeds in the United States (U.S.) invading forests, farmland, and natural areas. Managing Cogongrass presents significant challenges in the southeastern U.S., where single control methods have proven ineffective, necessitating an integrated approach that combines various methods. This study explored the nutritional challenges posed by Cogongrass for a classical biological control. Here we assessed the effects of Cogongrass varieties, nutrient levels, and leaf age on plant quality and performance when fed to a common insect pest that feeds on many grasses. We measured plant nitrogen, leaf toughness, and silicon. To examine the nutritional challenges of Cogongrass, we used a model organism, the fall armyworm (FAW) as a surrogate for approved biological control agents. Plant variety, nitrogen and leaf toughness significantly affected FAW performance. Larvae fed young Cogongrass leaves from high nutrient plants of the northern lineage had 75% survival compared to no larval survival on any southern plants regardless of leaf age and fertilizer level. When larvae were fed a preferred host St. Augustine grass, larval survival was similar but nearly all performance and nutritional indices were greater than those fed the high nutrient, young leaves of the northern Cogongrass plants. Associated with this difference were higher foliar nitrogen levels and lower leaf toughness in St. Augustine. These results suggest that agents developed for the biological control of Cogongrass must be able to feed and develop on plants that range widely in leaf nitrogen and toughness as these were found to be significant nutritional challenges that impeded feeding and development of FAW.

Technical Abstract: Nutritional differences in invasive plant lineages may influence herbivore survival and performance. Understanding the variation in plant quality and herbivore responses could assist in the selection and prioritization of potential species being developed for biological control. The two primary lineages of the invasive grass, Imperata cylindrica, have separate origins and mostly separate distributions occurring in Alabama/Mississippi (AL-type) and Florida (FL-type), USA. We conducted laboratory experiments with a generalist herbivore Spodoptera frugiperda (FAW) to examine the nutritional differences posed by the I. cylindrica lineages and leaf ages when grown at different fertilizer levels. The plant quality factors examined included leaf nitrogen, toughness, and silicon. Plant lineage influenced leaf nitrogen, and to a lesser degree, toughness but not silicon. Larvae fed young I. cylindrica leaves from high nutrient AL-type plants had 75% survival compared to 0% survival on all FL-type plants regardless of leaf age and fertilizer level. For comparison, larval survival was 100% for larvae fed a preferred host, Stenotaphrum secundatum which had higher foliar nitrogen levels and lower leaf toughness relative to AL-type I. cylindrica plants. The larvae compensated for the lower nutrient level of AL-type I. cylindrica plants by increasing total consumption, although this adjustment was only partially successful and resulted in lower biomass and greater development time. Biological control agents developed for this weed may face lower survival and reduced performance when fed different lineages that vary nutritionally. Similar challenges for biological control agents may occur in other weeds with multiple invasive lineages.