Parasitoids Associated with the Brown Citrus Aphid, Toxoptera citricida, in Florida

The brown citrus aphid (BrCA), Toxoptera citricida (K.irkaldy), is one of the most serious pests of citrus. Aside from the damage it causes by direct feeding, it is the most efficient vector of the citrus tristeza closterovirus (CTV). BrCA was responsible for the rapid spread of CTV in Argentina and Brazil in the 1930s and 1940s that caused the destruction of the citrus industry on sour orange rootstock (Knorr and DuCharme 1951 ). Prior to 1980, BrCA, presumably native to eastern Asia, was known to occur throughout the citrus-growing regions of Asia, Australia and South America (Yocomi et al. 1994). The aphid expanded its range throughout most of the Caribbean Basin between 1989 to 1994 and was first discovered in Florida in November 1995 in Dade and Broward counties. Since then, it has rapidly spread throughout most of the citrus-growing areas of southern and Central Florida (Halbert et al., in press).

Biological control may be useful in an integrated pest management approach combining other control strategies such as cross protection, tolerant and resistant rootstock and scions, limited pesticide use, and transgenic plants with resistance/tolerance to CTV (Yokomi et al. 1993 ). Preliminary results of a survey of the natural enemies of the BrCA in Florida initiated in 1996 have detected several predators ( especially Coccinellidae) and two parasitoid species that attack BrCA. To date, Lysiphlebus testaceipes (Cresson), a native parasitoid that attacks several species of aphids, has accounted for the great majority of parasitoid recoveries from BrCA. In addition, Aphelinus gossypii Timberlake, which was introduced into Florida from Hong Kong in 1963 for the control of Aphis spiraecola Patch, has been recovered from BrCA, but is much more commonly reared from other aphid species. Four species of hyperparasitoids, Alloxysta megourae complex, Ceraphron sp., Syrphophagus aphidivorus (Mayr) and Pachyneuron aphidis (Bouche) are assumed to parasitize L. testaceipes larvae inside BrCA.

Three exotic parasitoid species have been imported into Florida as biological control agents of BrCA. Lysiphlebia japonica Ashmead, imported from Japan in 1996, was released at various sites in southern Florida; however, very few recoveries of this species have been made in subsequent collections. Lysiphlebia mirzai Shuja-Uddin was imported into Florida from China in 1996, but has not been field-released. Aphidius colemani Vierick, imported from Chile, is currently being tested for efficacy on BrCA and has not been field-released. Plans are currently being made to import other Asian parasitoid species into Florida. One of these, Lipolexis scutellaris MacKauer is included herein because it will likely be introduced into Florida in the near future.

We provide a key and illustrations of parasitoids and hyperparasitoids associated with BrCA as it pertains to Florida to assist studies on the biological control of the aphid. Please note that the fore wing of each species is drawn with the wing setae excluded.