Carneocephala floridana, an oligophagous leafhopper that inhabits the
salt marshes along the coasts of Florida, utilizes Borrichia frutescen
s and Salicornia virginica (both herbs) as primary summer hosts, but u
ses two grasses, Distichlis spicata and Spartina alterniflora, during
the winter. We tested whether the seasonal patterns of abundance and a
pparent host-switching by Carneocephala are related to plant quality.
In laboratory experiments, nymphs of Carneocephala reared on nonfertil
ized control plants of the two herbs produced adults that were similar
in size to field-collected insects. Only Carneocephala raised at the
lowest densities on Spartina and Distichlis from the highest fertilize
r treatments produced adults similar in body mass to those reared on n
onfertilized Borrichia and Salicornia. For Distichlis, superior qualit
y (high foliar nitrogen) plants were able to mitigate the negative eff
ect of nymphal crowding on adult body mass. However, laboratory fertil
ization regimes produced an extremely high foliar nitrogen content in
the two herbs and the organic acid concentration in the xylem fluid of
Borrichia, the only host species suitable for xylem fluid extraction,
increased 2.5- to 3-fold. Total amino acid concentration in the xylem
fluid of fertilized Borrichia decreased compared to nonfertilized pla
nts. Carneocephala demonstrated reduced feeding efficiencies on high n
itrogen Borrichia. Our results suggest that Carneocephala prefers, and
performs better on, plants with high nitrogen content up to a thresho
ld, beyond which high nitrogen levels result in reduced leafhopper fee
ding rates and assimilation efficiencies.