Distribution of the Specialist Aphid Uroleucon nigrotuberculatum (Homoptera: Aphididae) in Response to Host Plant Semiochemical Induction by the Gall Fly Eurosta solidaginis (Diptera: Tephritidae)

Abstract

Many plants use terpenoids and other volatile compounds as semiochemicals. Reception of plant volatiles by conspecifics may trigger a defensive phytochemical response. These same compounds can also function as host recognition signals for phytophagous insects. In this experiment, we find that when the specialist gall-forming fly Eurosta solidaginis (Fitch; Diptera: Tephritidae) attacks its tall goldenrod (Solidago altissima (L.; Asterales: Asteraceae)) host plant, the fly indirectly induces a phytochemical response in nearby tall goldenrod plants. This phytochemical response may, in turn, act as a positive signal attracting the goldenrod specialist aphid Uroleucon nigrotuberculatum (Olive; Hemiptera: Aphididae). Laboratory-based experiments exposing ungalled tall goldenrod plants to the volatiles released by E. solidaginis galls demonstrated a consistent increase in foliar terpenoid concentrations in ungalled plants. Analysis of tall goldenrod stem and gall tissue chemistry revealed induction of terpenoids in gall tissue, with a simultaneous decrease in green leaf volatile concentrations. Field experiments demonstrated a consistent spatial relationship in tall goldenrod foliar terpenoid concentrations with distance from an E. solidaginis gall. Both laboratory and field experiments establish consistent induction of the terpene β-farnesene, and that this compound is a strong positive predictor of U. nigrotuberculatum aphid presence on goldenrod plants along with plant biomass and several other foliar terpenoids. These findings suggest E. solidaginis induced phytochemistry, especially β-farnesene, may be acting as a kairomone, driving aphid distribution in the field.

Repellence or attraction: secondary metabolites in pepper mediate attraction and defense against Spodoptera litura

“…5,6 Secondary metabolites constitute a major part of plant defense against herbivorous insects, 7,8 as they can protect plants against insects via their repellent and antibiotic effects. [9][10][11][12] The term 'secondary plant metabolite' was first proposed by Friedrich Czapek over 40 years ago. 13 Plants have developed several mechanisms to protect themselves against insect herbivores, such as the release of volatile organic compounds (VOCs), 14 which can repel insect herbivores or can attract the natural enemies of these herbivores.…”

“…Plant resistance to insects refers to the ability of plants to avoid, tolerate, or compensate for the damage caused by insects 5,6 . Secondary metabolites constitute a major part of plant defense against herbivorous insects, 7,8 as they can protect plants against insects via their repellent and antibiotic effects 9–12 . The term ‘secondary plant metabolite’ was first proposed by Friedrich Czapek over 40 years ago 13…”