Plant-Herbivore and Plant-Pollinator Interactions of the Developing Perennial Oilseed Crop, Silphium integrifolium

Weight Gain of Spodoptera frugiperda Larvae (Lepidoptera: Noctuidae) on Leaf and Floral Tissues of Silphium integrifolium (Asterales: Asteraceae) Differs by Plant Genotype

Silflower (Silphium integrifolium (Michaux)) is a native North American relative of sunflower that is undergoing domestication as a perennial oilseed crop. As silflower incurs pest damage from multiple insect species, it is necessary to screen genotypes for their effect on insect performance such that more pest tolerant/resistant accessions can be incorporated into future silflower breeding programs. We present a bioassay protocol for silflower using the generalist herbivore fall armyworm (Spodoptera frugiperda (J. E. Smith)). In this study, fall armyworm larvae were placed on leaf and flower tissue from eleven silflower genotypes, one cup plant (Silphium perfoliatum (L.) (Asterales: Asteraceae)) genotype, and an inbred sunflower line (Helianthus annuus (L.) (Asterales: Asteraceae), HA89). Caterpillar weight gained during a 4-d feeding period significantly differed on leaf and floral tissue from different silflower genotypes, between the Silphium species (silflower and cup plant), and between Silphium genotypes and annual sunflower. Two wild silflower genotypes produced lower larval weight gain on both the floral and leaf tissue than all other genotypes, suggesting these genotypes have either lower nutrition or greater resistance to fall armyworm. However, nonsignificant correlations between larval growth on floral versus leaf tissue across all plant species tested and among all silflower accessions suggest insect performances on these tissue types in silflower are independent. Along with identifying germplasm of interest for silflower breeding programs, we established an easily replicable bioassay protocol using fall armyworm on silflower floral and leaf tissues.

Field Trapping and Flight Capacity of Eucosma giganteana (Riley) (Lepidoptera: Tortricidae) in Response to Behaviorally Active Congeneric Semiochemicals in Novel Silflower Agroecosystems

Simple Summary

Rosinweed is a novel perennial crop being developed for oilseed and biofuel in the midwestern US. A primary pest is the Giant Eucosma Moth (GEM). Little is known about the chemical ecology or flight behavior of adults, but many attractants have been identified from other closely related species. The goals of this study were to evaluate whether any of these compounds could improve the capture of GEMs on sticky cards in the field and determine whether the most attractive volatiles might affect flight behavior in the laboratory. We found that there was significant attraction to (E)-8-dodecenyl acetate, which may possibly be a component in the pheromone blend for GEM. Exposure to these compounds in the laboratory reduced flight capacity. Our results suggest these two compounds could be included in monitoring or management programs for the Giant Eucosma moth.

Abstract

Silphium integrifolium is a novel perennial crop being developed for oilseed and biofuel in the midwestern US. One of the primary pests in this system is Eucosma giganteana (Lepidoptera: Tortricidae). Little is known about the chemical ecology or flight behavior of E. giganteana, but many semiochemicals have been identified from other closely related Eucosma species. Some of these compounds include: (Z)- and (E)-8-dodecenyl acetate, (E)-9-dodecenyl acetate, (Z)-8-dodecenol, (E,E)-8,10-dodecadienyl acetate, and (Z,E)-9,12-tetradecadienyl acetate. The goals of this study were to evaluate whether any of these compounds could improve capture of E. giganteana on clear sticky cards in the field, and the most attractive volatiles might affect flight behavior on a computer-automated flight mill assay. We found that there was significant attraction to (E)-8-dodecenyl acetate in two years in the field, which may possibly be a component in the pheromone blend for E. giganteana. On flight mills, E. giganteana flew an average of 23 km in a 24 h period. The presence of attractive stimuli (e.g., (E)-8-dodecenyl acetate) had arresting properties and decreasing flight distance on the mill by 78 to 80%. The longest flight distances were registered in the morning (4:00–12:00) and were 1.8-fold greater than flight distances and durations at night (20:00–4:00). (E)-8-dodecenyl acetate may be useful in behaviorally based monitoring and management strategies for E. giganteana. Overall, our research expands the knowledge on the chemical ecology of adult E. giganteana.