Herbivory damage does not indirectly influence the composition or excretion of aphid honeydew

Recent research has shown that extrafloral nectar secretion by plants, which also attracts ants, is a defense inducible by herbivory damage. Our research addresses the question of whether plants can manipulate the honeydew secretions of homopterans as an inducible defense in response to herbivory in the same manner as extrafloral nectaries. We investigated changes in honeydew composition and excretion rate by the facultatively ant-attended aphid Chaitophorus saliniger Shinji (Homoptera: Aphididae) depending on the presence or absence of herbivory by caterpillars (Clostera anastomosis L.; Lepidoptera: Notodontidae) on their host plant, the willow Salix gilgiana Seemen. Our results found no evidence to suggest that herbivory damage to the aphid's host plant causes significant changes in aphid population growth, honeydew droplet volume, volume of honeydew excreted per aphid per hour, or composition of three abundant sugars in aphid honeydew as a result of herbivory damage to the aphids' host plant, suggesting that, in this particular system, the plant is not manipulating the aphids' honeydew output for its own benefit.