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Herbivore preference and performance: horse nettle beetle response to water status and two host species.
Sacchi, Christopher1, Mezzacappa, Lisa2, 1 2
ABSTRACT- We experimentally tested the response of the horse nettle beetle, Leptinotarsa juncta, to plant water status and to species identity of two Solanaceous hosts, horse nettle, Solanum carolinense, and cultivated eggplant, Solanum melongena var. esculentum. We predicted that horse nettle beetle preference for hosts and their performance on them would be influenced by both water status and by species identity of the native compared with the cultivated host. Preference for plants by water status and host species was evaluated in both field and lab experiments. In the field, there was weak but suggestive evidence of horse nettle beetle preference for horse nettle in the high water treatment. In lab preference studies, horse nettle beetles preferred low-water treatment eggplant leaves. In a non-choice feeding experiment to assess insect performance, horse nettle beetles grown on plants of both species under a single high water treatment grew to similar size through four instars. In a fully crossed, two-factor field experiment, second instar larvae performed best on eggplant in the high water treatment followed by growth on horse nettle in the low water treatment. These results provide mixed evidence for the influence of host water status and species identity on herbivore choice of host plants and their performance on hosts. Results will be interpreted in light of current theory about herbivore response to attributes of their hosts.
KEY WORDS: herbivory, preference and performance, Leptinotarsa, Solanum