Herbivores associated with Arundo donax in California.

Abstract

AbstractThe Old World grass, Arundo donax L. (giant reed), is a serious invader of California riparian areas, and its purported ecosystem impacts led to its consideration as a target for biological control development. However, the herbivore complex in the Arundo adventive range has not been characterized, so there is little information regarding insects that may hinder biological control efforts by interfering with the release of new agents or that could be promoted as augmentative biological control agents if they have a substantial impact on the target weed. Here we report the results of surveys in California, with emphasis on three presumably non-indigenous insects that inflict significant damage to the host. One is a shoot-boring wasp, Tetramesa romana (Walker) (Hymenoptera: Eurytomidae), with a range limited to southern California and that damages shoots generally less than 1 cm in diameter. A shoot fly, Cryptonevra sp., is also associated with shoot damage and often mortality of secondary stems. A third herbivore, the aphid Melanaphis donacis (Passerini), is widespread in the southern and central parts of the state but has less apparent impact to the host. T. romana and Cryptonevra sp. are currently candidates for biological control development and introduction from overseas locations. Their established presence in California suggests that efforts could be revised to focus on documentation of host ranges and impacts under field rather than in quarantine conditions, in anticipation of future re distribution in North America.