Use of sugar beet foliage by the introduced leafmining fly Amauromyza flavifrons (Diptera : Agromyzidae)

Laboratory and held experiments investigated the use of a nontraditional ho st, Beta vulgaris L. (sugar beet), by the leafminer Amauromyza flavifrons M eigen. In laboratory trials using leafminers from the northeastern United S tates where sugar beets are not grown commercially; female flies readily ov iposited on B, vulgaris even when a commonly used host, Saponaria officinal is L., was present. However, larval mortality was significantly higher on B . vulgaris than on S. officinalis and occurred at an earlier instar. Larval mentality on S. officinalis was significantly correlated with the number o f miners in each leaf, suggesting an effect of larval competition, whereas on B, vulgaris, larval mortality was independent of the number of miners in a leaf. Results from an experimental garden array in the northeastern Unit ed States showed that wild, unconfined A. flavifrons females will oviposit on B. vulgaris and confirmed substantial early larval mortality on this pla nt. Implications of female oviposition and larval mortality on B. vulgaris are discussed in terms of the probable spread of this ny to western sugar b eet growing regions.