Insects found on Araujia species (Apocynaceae, Asclepiadoideae) in Argentina

The results of a survey of the natural enemies of moth plant or “tasi”, species of Araujia (Apocynaceae, Asclepiadoideae), present in Argentina are shown in this paper. 57 species of insects were recorded of which 17 are cited as natural enemies of these species for the first time. Their specificity was determined and their potential use as biological control agents for Araujia hortorum Fourn. was hypothesized. Pseudosphex noverca Schaus (Lepidoptera, Arctiidae), is recorded for the first time in the Buenos Aires province, Argentina.


INTRODUCTION
Few systematic studies have previously been carried out on natural insect enemies of native plants in Argentina. The well known listings of Bosq (1937Bosq ( , 1940Bosq ( , 1943 and more recently of Cordo et al. (2004) put emphasis on species that are important in agricultural crops, as until now, that is the sector where most surveys have been conducted.
The present study is part of a project on the biological control of Araujia hortorum E.Fourn., an invasive species in New Zealand. A survey was undertaken during 2004-2008, in Argentina and neighbouring countries, of the insect species found on A. hortorum, as well as on related genera and species, that could be of potential use as biological control agents of this plant in New Zealand.
In preliminary reports Winks & Fowler (2000) and Winks et al. (2004), a total of 19 insect species found on "moth plant" (A. hortorum) are cited in Argentina, data that was later included in the "Catálogo de Insectos Fitófagos de la Argentina" published by Cordo et al. (2004). Villamil et al. (2005) later added 35 species to the list of phytophagous insects and predators found on A. hortorum and other species of the same genus (A. angustifolia (Hook. & Arn.) Decne., A. sericifera Brot., A. odorata (Hook. & Arn.) Fontella & Goyder and A. brachystephana (Griseb.) Fontella & Goyder). That list was the result of surveys undertaken in the south of Buenos Aires province and in the Argentine mesopotamia (provinces of Entre Ríos, Corrientes and Misiones). Only 10 of these species (found on five species of the moth plants studied) were identified (21 % of the total number of species).
In the present research, the study area was extended to the north and centre of Argentina, but the focus was on the north of Buenos Aires province which is considered as the most important area in Argentina as most species of moth plant studied are found there, both in anthropogenic and pristine areas. Two other species of Araujia are included in this study: A. megapotamica (Spreng.) G.Don. and A. plumosa Schltdl. Some insect species are proposed as biological control agents of moth plants and their use is justified.
The authors have developed this research using the traditional approach, which considered Araujia and Morrenia as distinct genera (Meyer, 1944, here referred as sensu antico). Nevertheless, recently both genera have been brought together as Araujia (Rapini et al., 2011, here referred as sensu novo).
From the species found during the development of this project have been chosen by Landcare Research (the project sponsor) and preliminarily evaluated in laboratory, Colaspis argentinensis (Bechyné) (Coleoptera, Chrysomelidae) and Toxotrypana australis Blanchard (Diptera, Tephritidae).

MATERIALS AND METHODS
The specimens studied were collected in jars with 70 % alcohol and were deposited in the Entomology collection in the Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" to be studied and stored.
The insects and plants, has been determined by comparison with reference collections, both in the collection of the Division of Entomology Museum of Natural History and the herbarium of the Universidad Nacional del Sur.

RESULTS
These are the final results of the survey of natural enemies of Araujia, after five years of field work (2004)(2005)(2006)(2007)(2008). The authors have added 17 new natural enemies to the preliminary lists.

Record of herbivorous insects reported on different species of Araujia in Argentina
Featured here is the list of species found and published in the reports of the various campaigns conducted between 2000 and 2008 (1) Species cited in Winks & Fowler (2000).

Results of the 2004-2008 survey
Fifty seven species of phytophagous insects were recorded on the nine species studied of Araujia, and some other Asclepiadoideae, of which 46 were identified to species level and eight to the genus. Another 12 unidentified mor-Another 12 unidentified morphotypes cited in Villamil et al. (2005) were also included with brief comments.
Of the total of 57 phytophagous species studied it is concluded that: The following 24 species are not very important as they are polyphytophagous:  Winks & Fowler (2000). Y. Pest/host associations mentioned in Villamil et al. (2005). Z. Pest/host associations mentioned in Villamil et al. (2006). Z. Pest/host associations mentioned here for the first time. 1. Pests on more than one species of Araujia or Morrenia (both in sensu antico). 2. Pests found only on different species but only on Asclepiadaceae. 3. Specific pests on one of the moth plants studied (monospecific pests). ?. No data. Species without numbers are polyphytophagous (also present in other plants not Asclepiadaceae). Table 2. Characteristics and potentialities of herbivorous insect populations found on different species of Araujia. Definitions of frequency categories according to Winks et al. (2004): rare: fewer than five individuals collected in total. occasional: a total of 5-24 individuals collected, or present at fewer than five sites. common: 25 or more specimens collected and present at five or more sites. abundant: more than 200 individuals collected and present at 10 or more sites. These data may be relative because damage caused by, for example, 10 larvae of Rhyssomatus, is greater than damage caused by 500 Aphis nerii. Different feeding habits according to Winks et al. (2004)