Host Preference and Recognition by the Goldenrod Ball Gallmaker Eurosta solidaginis (Diptera: Tephritidae)

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Abstract
Goldenrod ball galls produced by Eurosta solidaginis are almost invariably found on Solidago altissima in central Pennsylvania [USA] even though they occur on several other Solidago species elsewhere within the range of E. solidaginis. In two no-choice experiments, S. altissima was strongly preferred by Pennsylvania Eurosta relative to the sympatric species S. gigantea, S. canadensis and two ploidy levels of S. rugosa. A third experiment was conducted to determine if chemical and/or tactile stimuli sensed by the female fly''s ovipositor serve as cues for host recognition. Buds of S. altissima and S. rugosa were wrapped with bud leaves from S. altissima and presented to mated female flies. The flies punctured the wrapping leaves with their ovipositor on both plant species with equal frequency, but only the wrapped buds of S. altissima were punctured and used for oviposition. The wrapped S. rugosa buds were not punctured indicating that the E. solidaginis females can sense physical and/or chemical features of potential host plant buds with their ovipositor. Our data suggest that host affiliation patterns in Eurosta are the result of herbivore behavioral preferences that are selected for by host suitability.