Phototaxis, host cues, and host-plant finding in a monophagous weevil, Rhinoncomimus latipes

Rhinoncomimus latipes is a monophagous weevil used as a biological control agent for Persicaria perfoliata in the eastern United States. Density of adult R. latipes and resulting feeding damage has been shown to be higher in the sun than in the shade. This study aimed to determine whether phototaxis, sensitivity to enhanced host cues from healthier sun-grown plants, or a combination is driving this behavior in the weevil. A series of greenhouse choice tests between various combinations of plant and light conditions showed that R. latipes is positively phototactic, responsive to host cues, and preferentially attracted to sun-grown plants over shade-grown plants. From our experiments, we hypothesize two phases of dispersal and host finding in R. latipes. The initial stage is controlled primarily by phototaxis, whereas the later stage is controlled jointly by host cues and light conditions.